Cozy Beehive

Some Probability And Statistics On The Individual Time Trial

noreply@blogger.com (Ron) — Thu, 05 Nov 2009 07:01:00 +0000

The Tour de France (TDF) is the marquee cycling event on the calender for any top international pro cyclist as well as their squads. Everyone wants to do well here because its arguably the biggest and most glamorous stage for displaying athletic talent. The competition is tough, the fans are many, the stages are epic and the prize money is fat.

In this post, I'm trying to figure out what kind of a statistical distribution is seen in the finishing times from this year's prologue TT (Tour de France). I will also try to quantify the probability of getting close to the fastest time trialist in the world. Alberto Contador tried pretty darn well. How well?

Only one way to find out these things.

So here's what I did.

Step 1 : I obtained Cyclingnews.com data for the TDF Prologue TT on July 4, 2009. I obtained 180 data points corresponding to all the competing cyclists.

Step 2 : To make sense of this data clutter, I put them into Microsoft Excel 2007 and ran a descriptive statistics analysis on it. Here's what I obtained. What you're about to see is powerful.

Fig 1 : Descriptive statistical figures for the finishing times of a sample set of 180 cyclists from the Tour de France 2009.

So is my sample set taken from a normal distribution or something different? Let's try to answer that reasonably with the table above.

The mean, median and mode are very close to each other which MAY indicate its normally distributed. The average of the average deviation of each cyclist from the mean was 0.63 min or 37.8 seconds. The minimum time belonged to Fabian Cancellara, with a blitzy 19.53 mins whereas the maximum time belonged to Yauheni Hutarovich. I also have a Kurtosis and Skewness of 0.558 and -0.068 respectively.

Positive Kurtosis indicates a relatively appreciable peak which makes me suspect the distribution is leptokurtic (too tall instead of normally high). The book Using Multivariate Statistics (Tabachnick & Fidell, 1996) explains that if my Kurtosis statistic is more than 2 times [sqrt(24/180)] = 0.73, the data is not normally distributed. Since 0.558 is less than 0.73, we're ok.

Negative Skewness indicates that my data is left skewed. The same book mentioned above explains that if my Skewness statistic is more than 2 times [sqrt(6/180)] = 0.365, the distribution is not normal. Since -0.068 is less than 0.365, we're ok here as well.

Step 3 : The above only gives rough indications of the type of distribution. Nothing beats setting up a visual of the spread. So I made a histogram, with a chosen bin width of 0.20 min.

Fig 2 : The histogram for the data set. Please see source of data on CyclingNews.

The graph agrees with the skewness and kurtosis statistics. The data has central tendency but is ever so slightly skewed towards the left. This is the data for the best cyclists in the world. Not really a Gaussian, but not too far away from it either. What kind of distribution it is will take more analysis and tests for goodness of fit, which I'm going to tackle some other time.

So What Does All This Mean?

Looking at the data and Fig 2, we can say that the course conditions in Monaco on that July day were such that nearly 48% of all 180 cyclists managed to get times below the average, which might mean they were pretty fit and came well prepared (or something else worked in their favor which I can't quantify). Thus, the 48th percentile is the average time, i.e 21 min and 30 seconds.

To put it in another fashion, the probability of a world class cyclist racing on this course in a time less than the average time is 0.48.

52% of the 180 performed under par, with about 8% of those 52 giving exactly average times. The probability is 0.52 that a cyclist is at average time or above it on this course.

We can also say that 72% of the 180 cyclists lie between one standard deviation on both sides of the average, 93% lie between two standard deviations about the average and 99% lie between 3 standard deviations. Pretty close to the 68-95-99 rule obeyed by normal distributions eh?

Alberto Contador Vs Fabian Cancellara As Time Trialists

Our last question is the most interesting. So if you're a top pro at the peak of your abilities, what are you chances of ever getting close to Fabian Cancellara's blitzkrieg results? Then the next question would be, how close do you want to get to 'Spartacus'? Within 2%? 3%?

Let's do 2% as a start. Within 2% is 23 seconds difference. Now that's probably the limit of what a time trialist can accept to cap the gap, so to speak!!

Let's look at what Contador obtained that day from the data. Bert raced the course 18 seconds slower than Cancellara for an amazing second place. In other words, there was a mere 1.54% time difference between the best all round cyclist in the world and the fastest time trialist in the world. Just 4 cyclists managed to come within 2% of Cancellara's time - Contador, Wiggins, Kloden and Evans. 4/180 = 0.02 = 2%.

In other words, just 2% of the 180 cyclists got a time less than or equal to 19 minutes and 55 seconds (this 2% window we're talking about).

Put in another way, this is the 2nd percentile. This is where the glory is at. And the money. And the kisses from the long legged European girls.

The probability that you're in this 23 second window from the best man on the bike is low. Just 0.022 or 1 in 45 chance. Keep in mind this is for the best in the world.

Now you know why you and I are not racing in the Tour de France. Let's just scratch our butts and cheer these beasts on.

* * *

2009 Weblog Awards - Nominate & Vote For The Bee!

noreply@blogger.com (Ron) — Wed, 04 Nov 2009 00:00:00 +0000

Hey everyone. So a little about me again. I'm a mechanical engineer currently dabbling in electro-optics full-time after quitting my previous job in the petroleum industry. On the side, I survive through a rabid fascination for cycling and its many aspects, from tech and history to culture.

For the past 3-4 years, this blog has given you varied articles that many of you love and use as reference/research. Some are so controversial they are discussed on forums to the point where people trade barbs with each other. Popular posts such as Serious Cycling=Serious Legs, Power to Weight Ratio, Lore of The Victory Salute, Church Of Lance Armstrong, The Ideal Weightweenie and numerous others are staples of this blog.

Even though I'm not as HUGE as some of the other blogs people read, I will tell you one thing right away. No individual cycling blogger might come close to the variety of topics I write about in depth or the quality of links I pollinate. I say that pretty proudly unless you show me another.

In fact, the kind of readers I get stands testimony to the site's popularity and strength of content. I receive periodic attention from MIT Engineering and Design, U of Delft, Cornell, and various other American universities who use my blog to even engage students in the classroom.

Bikers who work with Lockheed Martin and the Boeing Company have conversed with me in the past. Two big cycling companies approached me soliciting employment offers after the blog, safe to say, impressed them. Not to exclude, authors of best-selling cycling books and inventors of cycling products are also in this company of readers. The average time spent by a reader is about 3 mins and 6 seconds. Now I consider that PLENTY for the fast paced, attention deficit disorderly world we live in today.

For the folks among you who aren't so technical minded, I write quite a number of general articles and share my perspectives, both on the serious and the funny side of things. I make great efforts to make articles readable by all, regardless of nationality. In fact, over the past one year, I have been attracting lots of readers from South America, India and China who share an equal love for cycling but may not be very talented at the English language. I'm pretty sensitive to that issue. I think English by far is the hardest language to master. Anyone disagree?

While content is free to all, I haven't always felt that I'm not doing a thankless job (I'm human afterall). Now you can get to show your annual appreciation by nominating and voting for Cozy Beehive towards the 2009 Weblog Awards. Turns out, there's no prize money or medals offered, but the recognition will go a long way. Last year, I was a finalist in the category of Best Sport Blog but didn't go any further as the competition was just too stiff out there.

All relevant details on how to nominate and vote can be found on the Weblog awards website. See Nominations FAQ and the list of nominations page where you may vote for my blog against what you feel I deserve! See you all there!

Meanwhile, any of you who are serious about blogging and pay attention to content must join the party too!! Ok ok, I'll cut out the sales pitch now.

ADDITIONAL RESOURCES :

CompetitiveCyclist.Com : Cozy Beehive Blog Review (Top 2)
2009 Weblog Awards Voting Page - Nominations Master List

* * *

Battling The Tour de Off-Season

noreply@blogger.com (Ron) — Sat, 31 Oct 2009 05:35:00 +0000

Cattaraugus, NY

For many here in the northeast of the U.S, crusty golden leaves have begun to fall, signaling the time of the year when we must take give our a nuts a break off the bicycle saddle and gather other edible nuts for winter.

We are to find out our losses in upper body strength and try to "cross-sport", which must be like "cross-dress" to those 50-50 human beings, you know...to find out what the other exciting side of the grass is like.

After emptying the family budget throughout the year buying bicycles, racing bicycles and driving huge vehicles to buy them and then hauling them around like a Bedouin to race them all over the place, we are going to try new things, lust after new gear, and bring the family budget to negative on the number line.

We're going to spend night in and night out of Ebay worse than a prostitute in a red light district of Bangkok, bidding on this crankset and those wheelsets and that headset because our well, our headset up there on the shoulder is a little out of torque, we're not satisfied with what we have and think we could be faster with the fancy colored ceramic bearings originally designed for machines that churn out raw materials for society in excess of 20,000 rpm. Nope, we must have it.

Not to mention, such night sessions of Ebaying will take a toll on us as we gain weight each day by the pound.

Sometime later, we'll start the "training" again and buy loads of cycling books to read because turns out, none of us know zilch about mambo-jumbo like periodization and TSS and FTP and BSS and all that BS.

When the training kicks in, it comes in myriad forms like wind trainers and rollers and fancy virtual reality and scandalous indoor spinning classes. For those of us who can't afford any of the above, we'll just pretend to spin a high gear in the bathroom while showering and then do calf raises after that, and somehow get the impression those legs will get big in the hot water over a couple of months. You know, the air-cycling version of air-guitaring.

Oh and must I say, half the training mentioned above will be consumed in trying to get rid of the weight we put on in winter. The other half lands us precisely to the fitness level we started out last year. And then we walk proud and upright with an S-curve in the back thinking we are stronger cyclists. Note : This is not applicable to those of who air-cycled in the bathroom as most of them will slip and fall on their bottoms in soapy water anyway.

The final stage of this Tour de off-season comes when renewing races licenses and buying extra licenses and so on, just in case one got lost, voila, not to fear here's another one in my organizer. Cat 1, cat 2, cat 3...what's that mate...is that a part of the cat family? Do they snarl?

When all is said and done, its a great off-season and its the journey that matters, yeah?

By the way, why the heck do they even call it off-season? There's nothing off about this silly affair.

* * *

Happy Halloween and yes, have a great....off season !!!

A Word On Bicycles And Radios

noreply@blogger.com (Ron) — Thu, 29 Oct 2009 17:27:00 +0000

Think back to a great speech, an interesting musical composition or an experience of going through a historical event live and chances are, you probably heard a good portion of them on the radio.

Riding a bicycle and going places also instills deep memories. In developing nations, kids ride bikes to school. Men make money through bicycles. Entire families are seen transporting themselves from village to town and vice versa. For most of us, we remember routes and places better when we take a trip there by bike.

One could argue that both the radio and the bicycle completely changed human society, and the way we live today. They are metaphors for social progress. The bicycle has offered a cheap means of transport for millions of people across the world for over a century. It increased personal freedom, elevated personal health and has had pivotal roles to play in the emancipation of women.

And without the radio and closely related wireless technologies, perhaps the Allies wouldn't have even ended either of the World Wars. I mean, there's nothing more gripping and nervous than the threat of war, I'm sure we can all agree to that. So imagine conducting battles, moving tens of millions of people and resources across nations, directing complex artillery to places you cannot even see and making concerted decisions relevant to governance, information and security via horses, mail coaches and pigeons.

The radio has been a cheap information source. We don't have to know what's in it. There's a fantastic level of abstraction to this technology. The package is great! And through the ether or whatever that stuff is up there, it brings us music, tidings, propaganda and sports broadcasts. All we have to do is sit somewhere and turn the knob to the right places. Then shut up and listen. Its simple and beautiful.

The bicycle takes a day or two to learn. Okay, at most 10 days, maybe a fortnight. But the thrill of finally getting to ride one must far overwhelm the initial effort. Once on a bicycle, the rider is in tune to everything around them - the breeze to the face, the direction of the wind, the inclinations of pathways, the people and the surroundings, the quality of the air, the temperature gradients, the sounds on the bicycle. Its a self discovery. Its a discovery of the environment. Its a discovery of mechanisms and how they work.

Should bicycling be like using the radio? Yes, of course. It should be easy to use. So easy, a caveman could do it, that sort of thing. It should be like the radio as an instrument that helps tune personal development, giving the owner great education, memories and pleasure. Riding a bicycle should have an imaginative component, like listening to a radio. It should be a tool promoting shared experiences. Hundreds of people can listen to one great radio broadcast and enjoy it. Hundreds of bicyclists can ride the same beautiful countryside on the same bicycles and enjoy its lush offerings. Why, that concept has been enjoyed by many people for many years.

Should the bicycle be as complex as the radio? The radio is complex and its there for a reason. But the complexity is hidden through abstraction. All we see is the outer case and a couple of knobs. But if something goes wrong with it, we have to sit and RTFM - Read The Fine Manual. If its necessary, you must take it to a specialized individual to have it fixed.

Is it necessary to pollute the bicycle with unneeded complexity? I guess it depends how you think about that. Here's what I feel. Not considering bicycles used purely for specialized hobbies, the common bikes that people ride for transport and living must be kept simple to a large degree. Most normal people equate happiness with simplicity. It must feel great to have a tool that's easy to use and is easy to figure out what's wrong if something does go wrong. And how nice it would be to have one that you can use and carry around with you in many places, akin to the mobility offered by the simple radio.

Enjoy this video from Rwanda,. As we can see, there must be something deeply existential in fitting a radio to a bicycle. Can you relate to this special joy?

* * *

Velo Taboo : Underwear Inside Shorts

noreply@blogger.com (Ron) — Tue, 27 Oct 2009 15:08:00 +0000

Attention Cycling Noob,

Just where do you think you're going?? Are you wearing underwear, knickers, lingerie and ofter hardware under your cycling shorts?? If yes, just imagine someone plugged out a huge 8ft stop sign from the ground with utmost urgency and stuck it in your face while an elephant provides the mother of all trumpeting!

Wearing underwear under padded cycling shorts is like riding with your shorts full of broken glass. I mean, imagine someone exploded a Schott glass with dynamite and then slipped the remains from a laboratory funnel right into your shorts. Happy trails!

And we did not even get to the most important part YET.

If you've got cheesy flowers, Mickey Mouse and other nonsense on the underclothing, they'll show through your colored Lycra shorts which will obviously knock the person drafting behind you out of consciousness. Which will then knock the others behind them out of line and others behind them out of their lines... and so on and so forth, until you're all done with a wonderful zero mile ride and all you've done all day is collecting loose pieces of skin from the road to piece yourself together.

Oh..alright...maybe if you're the type of bloke who likes to shoot for a Nobel Peace Prize in microbiology, we might be able to understand why the multitude of fungal infections harvested from the bulbous boils around your nether regions are of any immediate use to you.

So unless you're the above, or you're pulling off a gimmick as an underwear salesman or just someone really bent on publicly exhibiting the variety in the underwear drawer, please oblige and do us all a favor.

While you're changing in the restroom, we'll be having a long talk with your mom.

ADDITIONAL READING :

ShamWow Shammies

* * *

Saturday Stupidity VII

noreply@blogger.com (Ron) — Sat, 24 Oct 2009 04:00:00 +0000

FOR PREVIOUS INSTALLMENTS OF STUPIDITY, SEE :

Saturday Stupidity I
Saturday Stupidity II
Saturday Stupidity III
Saturday Stupidity IV
Saturday Stupidity V
Saturday Stupidity VI

* * *

E-Hub Marketing : A Important Lesson In Statistics

noreply@blogger.com (Ron) — Thu, 22 Oct 2009 15:48:00 +0000

Like the past 100 years, even today cycling products come and go. And with them, so do their marketing sound bytes...

Any intelligent cyclist must carefully inspect marketing data handed to him, and question what is missing and why its missing. Weak data can lead to weak correlations, spurious percentage differences and other logical fallacies. Until the missing numbers are accounted for, I don't advise anyone to take faith in where they put their money.

When James posted a small article yesterday on the E-Hub at the Bicycle Design blog, I got very amused and decided to take a peek at the product website. I spent a little time looking at the interesting item proudly displayed but then had an itching desire to see the numbers behind the invention. Not just plain numbers. I wanted to see if they're meaningful numbers.

This page has a statement from Dr. Alen Orbanić (a University mathematician from Slovenia) telling us that the designers behind the innovation carried out a surefire experiment to prove without doubt that using the E-hub for cycling showed the following things :

1) Increased average power output when compared to cycling with a conventional rear hub.

2) 4% reduction in average and maximal heart rates in cyclists using this product, when compared to the same figure for cycling with conventional hub.

3) 10-15% of blood lactate reduction using the E-hub versus using a conventional hub.

So What Was The Experiment?

Well, I'll tell you the part of it they conducted outdoors. They brought together a population of cyclists from 20-60 years of age. How many? Not specified. Then they categorized them as "Professionals", "Recreational" and "Amateurs". How did they define who belonged where? No indication. What were their weights, fitness levels etc? No indication.

So this population of cyclists were asked to fit themselves with a Polar heart rate measuring system who then mounted Ergomo powermeter fitted MTBs to ride a 2km track (1.24 miles) with 14 degrees of average inclination. Apparently, they did this twice, one with the E-hub and one with a classic hub after 24 hours of rest between the two. Levels of lactic acid were measured twice, immediately after each run with a hub.

Fig 1 : A snippet showing how things were measured by the authors. Typos abound. Click to zoom.

I'm surprised a tad bit by two things. 14 degrees of average inclination? Wow. That is an average of 25% grade. Second, I'm surprised recreational cyclists could manage this effort. Either Slovenian humans are exceptional, or the drive train was really dumbed down for spinning, or something is just plain wrong with this number presented to us. I have written in the past about the W/lb required to maintain a certain speed on a given grade.

So What Does The Data Look Like?

The authors go on to claim they gathered a "vast quantity of data" but for the sake of the reader's reading convenience, they picked 3 'random' data points corresponding to 3 cyclists, for each class of cyclist. I guess this is a solid example of where you can't really thank people for their kindness :).

Here are the numbers :

Fig 2 : 3 randomly selected cyclists in each class showed the above numbers with and without an e-hub. And how were they randomly chosen? No indication so could we not say this is an example of data mining?

Fig 3 : % differences in heart rate and power between the two hubs.

Fig 4 : % differences in average blood lactate between the two hubs.

Right off the bat, I see this is poorly presented data, at least for a professional level. From the surface, I can come up with 3 weaknesses :

1. Sample Points & Averages : There's a rule of thumb in good statistics. You need a minimum of 30 sample points before you do descriptive analysis on it to explain trends.

Take a look at the amount of power these cyclists are producing on this so-called 25% grade, 1.2 mile track. Professionals are producing puny average power outputs while recreational and amateurs are easily rivaling them, not only in power but also in speed.

This leads me to question firstly how the authors classified and defined these cyclists. It seems to me from this meager amount of data that all three classes were almost equal in their cycling abilities?

I also have to say that averages can fool you if data jumps all around the place wildly. For the meager sample points presented above, you can see that the average power is pretty sensitive to outliers.

Infact, if we had been handed 30 sample points or more for each class of cyclist, it is likely the data could have shown a decreased average power, which could have reduced the resultant power differences between the E-Hub and the classic hub. Any guarantee that's not the case? The authors haven't proven it here but go on to artificially bump up the averages using just 3 data points mined from here and there. Furthermore, their conclusions about the apparent efficiency increase with the E-Hub is only relevant for these 3 sample points.

2. Spread : Closely following the absence of more samples is the question, what's the spread and deviation of this "vast amount" of data? I don't have any idea of it as there's no indication of standard deviation. The data is meaningless. How can I tell if a majority of data points in this experiment are close to the average power output or not? What if outliers are pushing the average up?

3. Range : Because only one sample data point (for power, HR and lactic acid) have been presented to us going across for each cyclist, we have no idea of the true range, or the true maximum and minimum values that would be observed. The data point presented to us is just one of what could be many and they are all bound to vary, because that's how all processes are... they vary! Hence, the range could vary pretty significantly if we had more tests on the same individual.

4. Instrument & Measurement Error : Lastly, what about the instruments used? Were they calibrated properly and accurate to other power measurement systems? What's the bias in the system, if any? Are these numbers from just random variability or regression to the mean? It is often taken for granted by some that measurement systems (instrument+human operator) that produce such outstanding numbers are always pin-point accurate.

I simply have to conclude that this data, so far, to me is just meaningless. The rest of the data that follows on the webpage, done on an indoor ergometer, suffers from exactly the same types of weaknesses I have mentioned. These are basic rules to follow in statistics and I'm surprised they weren't in this case.

The product itself may be great. I cannot disagree for certain there. But the numbers don't show me much so far. Thus, I think the declaration that this hub system really improves the efficiency of a cyclist compared to what we usually use must be taken with a handful of salt.

* * *

Edge Composite 68 Carbon Wheel Failure

noreply@blogger.com (Ron) — Mon, 19 Oct 2009 13:18:00 +0000

Our protagonist, the author of a blog called "Manley Man", had recently participated in Levi Leipheimer's GrandFondo ride in California. Among the highlights of this ride are really steep descents, some of which feature blind corners.

One of these, called Meyer's Grade Road, was an 18% grade technical downhill and the Manley Man was being pretty cautious going down this road, hitting his brakes every now and then (okay, 'every now and then' maybe a huge assumption from my side). Yet, towards the bottom of the descent, he found things out the hard way. Observations were described thus :

"Toward the bottom third of this descent I felt a very bad pulsation in the front brake lever. I looked down at the front wheel to see if there was something wrong but there wasn't anything visibly bad. But it was scary to see the fork flexing back and forth under braking; it probably was oscillating at least an inch when I had the front brake applied heavily.

I got to the bottom of the descent and my teammate pulled over a few seconds later to see how I was doing. I spun the front wheel and it got stuck. It wasn't clear to me what happened. I opened the brakes up to let the wheel spin more freely. At this point I saw the issue. Initially it looked like the sidewall of my Rubino Pro had bulged out and was rubbing the break pads (yellow Swiss Stop). But to my surprise it actually was a deformity of the braking area of the rim! I had somehow managed to melt the carbon!"

Here's the deformed wheel, picture courtesy of Manley. The original specs of this clincher can be found on the product page. Because its a clincher wheel, the carbon braking track has to withstand the pressure inside the tire.

Manley Man limped through the rest of Levi's ride, being able to use what he estimated as only 10% of his total front braking power. He says that he'll be on the phone with Edge Composites having a long talk with them.

This kind of scenario has been a common topic of discussion on this blog and forums. If you'd like to get a little deeper into rim heating during braking, please see this past article. You may also notice that these kind of incidents happen not only with amateurs, but also professionals on the international stage. See this article.

Now we're all really really wondering what Edge Composites told the owner of the wheel. Will they have it replaced under warranty or pass on the blame to him with no gifts? Manley?

Do you want to discuss the specific nature of this failure? Please include your comments below.

ADDITIONAL READING :

Clincher Failure On Meyers Grade
Rim Heating During Hard Braking
Tubulars Exploding And Peeling Off
Bizarre H Plus Son Rim Failure In Japan

* * *

Analysis Of The Bicycle Endo

noreply@blogger.com (Ron) — Thu, 15 Oct 2009 05:02:00 +0000

The endo, short for end-over or end-over-end, is a type of pitch over crash where the cyclist goes over the handlebars, the weight offset of which causes an inertial moment to act about the front wheel resulting in rear portion of the bicycle to flip in the air above and behind him.

Usually, the cyclist, as a sudden reflex action, yanks out their hands or legs at some point to cushion the impending fall and ends up letting go of handlebar control. Meanwhile, the bicycle is bound to fall either sideways, due to its motion about the steering axis or right on top of the cyclist. In the latter scenario, the saddle or even the rear wheel itself could land on the cyclist's body.

Again, an endo is a crash that could cause injury. It is not a bicycle trick. That one has another name. Its called a 'stoppie' or a 'wheelie'. An endo is caused due to strong front wheel braking or when the bicycle hits a curb, a structure more rigid than the wheel itself. Endos may also occur if the front wheel is loose, i.e, if it is not secured properly to the fork dropouts by the quick release skewers.

In this post, we will cover the "endo parameter", study the relationship between braking force and endo parameter on level ground, outline some common reasons for endos, check out a video analysis of an endo and finally study the relationship between gradient of the road and endo parameter through a literature source.

ENDO PARAMETER

Braking a bicycle naturally upsets equilibrium and transfers weight to the front wheel. With a stark increase in the overall braking force, the load on the rear wheel approaches zero, after which the rear wheel will start to lift off the ground. Hard braking may stop the bicycle but Newton's first law reigns supreme as the cyclist's body continues in motion in the headed direction. This rider motion has some momentum. If not self-controlled, the rider will flip over the handlebars and the bicycle will pitch-over as well. What results is the endo.

It turns out that while outrageous situations cannot be helped, some factor of safety from bicycle design and rider positioning skill can provide for a cushion against pitch-over tendency in the above mentioned situations.

I'll call my main parameter of interest the pitch-over parameter (or endo parameter for lack of a better word) - A/H - as can be seen in the diagram below :

Fig 1 : Free Body diagram of a bicycle-rider system just at pitch-over. Now you may be able to appreciate from geometry and c.o.g as to why recumbents and tandems are stable in pitch-over. O is the point signifying the contact point of the front wheel with the ground.

TERMS :

W = combined rider-bicycle weight
Wf = normal load on front wheel
Wr = normal load on rear wheel
Ff = braking force at front wheel
Fr = braking force at rear wheel
Fb = braking reaction (mass times deceleration)
L = wheelbase
A = location of center of gravity (c.o.g) aft of front wheel
B = location of c.o.g forward of rear wheel
H = height of c.o.g

The endo parameter, A/H (a ratio), in the combined bicycle-rider system should be large enough to avoid front pitch-over. Obviously the vertical height, H, of the center of gravity (c.o.g) and the location of the c.o.g aft of the front wheel, A, are going to vary with variation in rider's weight, height and sitting position.

This highlights why its important to get a proper bike fit for the type of bicycle you wish to ride. Its not just a question about comfort. Its also a question about safety. Enlarged riders who overwhelm miniature bikes not made for their size will quickly find out what they're doing wrong. All they have to do is hit the front brakes hard and they're right on target to be turned into human projectiles.

Looking at the free body diagram above, we can deduce that the system is in static equilibrium about the front wheel contact point O if the sum of the moments due to all forces about that point is zero. In other words, rotation is just initiated at :

Fig 2 : Endo parameter relationship to braking force. This also gives us an expression for the braking force at the point of the pitch-over.

From this simple relation for level ground, we see that endo parameter is equal to the braking force as a percentage of total weight at just about the initiation of the endo. Braking force is a function of the co-efficient of friction at the tire-road interface.

Before the initiation of pitch-over, the braking force-weight ratio is lesser than the endo parameter. Well after the pitch-over has been initiated, the endo parameter falls lesser than the braking force-weight ratio.

We can now infer that making A/H larger is better for safety. Otherwise, a lesser braking force relative to total weight will be sufficient to initiate pitch-over. How? Simply because the braking force-weight ratio catches up with the endo parameter sooner. Oops.

A/H can be fixed to be greater with good bicycle design and proper fit. It can also be superficially made larger by the cyclist while riding by positioning his body rearward (relative to bottom bracket) as the following picture shows :

Fig 3 : A cyclist ducks and shifts his c.o.g rearward to increase his endo parameter

People succumb to pitch-overs because of other factors too. They may not be skilled enough to increase the endo factor, A/H. They also may not be skilled enough to modulate and may tend to hitting the front brakes really hard without realizing that a front brake can cause more deceleration than a rear brake. For comparison, front brakes generate upto 0.5g's of retarding force whereas rear brakes produce a max of 0.1 or 0.2g's. Note that maximum deceleration is limited by the co-efficient of friction between tire and road and the normal load.

You can notice front braking power for some mountain bikes through a speed vs time graph.

Fig 4 : Speed vs Time graphs of MTB's (Courtesy : Beck Forensics)

Obviously, the graphs show that you can bring a bike to a stop faster using the front brakes alone than the rear brakes. Using both brakes is even better for reducing stopping distance even further.

SEQUENCE OF MOTIONS IN AN ENDO

Beck Forensics did an interesting little video analysis of an endo. The following image as well as the snippet below it is taken from a web sampler of their book Bicycle Collision Investigation. It shows the steps involved in an endo before the crash.

A mountain bicyclist traveling at about 22.5 mph (36.2 kph) applies only the front brake. Once the front wheel is nearly locked, the rear wheel starts to lift up. At about 0.20 seconds, the rider really has no chance to recover. At about 0.33 seconds, he releases the brake and prepares his right hand, and then his left hand for landing. The cones are shaped in 25 foot (7.6 m) intervals and the grade is about -2% (descent). (Courtesy : Beck Forensics)

RELATIONSHIP WITH PERCENTAGE GRADIENT OF GROUND

This section is a little more involved. It uses the same analysis techniques shown above to derive a relationship between the "endo parameter" and braking force-weight ratio with the percentage gradient of the ground. You will see that the chances of an endo are more likely on a descent.

The following literature is from one digest of IHPVA (2001), written by a retired engineer named Frederick Matteson. Click on the series of images to zoom the text. Alternatively, you can also read the paper here.

Enjoy!

Page 1 : Click to zoom

Page 2 : Click to zoom

Page 3 : Click to zoom

ADDITIONAL READING :

Budbrake : Proportional Brake Control For Safer Bike Stops
Dynamic Stability Of Bicycle Design : Part 1
Dynamic Stability Of Bicycle Design : Part 2
Dynamic Stability Of Bicycle Design : Part 3
Dynamic Stability Of Bicycle Design : Part 4

* * *

Pedal Force Simulator : Capturing The Outdoor Experience

noreply@blogger.com (Ron) — Tue, 13 Oct 2009 04:00:00 +0000

Components of Pedal Force Simulator

Tom Compton, the personality behind AnalyticCycling.com, believes trainers do a shabby job of simulating outdoor riding conditions. There's that something missing in them.

Well, nothing new there, as most of us have felt the same since time immemorial. We all sit on these mechanisms and fool our brains into thinking we're doing the actual thing.

But what I like is that Compton expresses this "something missing" of trainers relevantly as follows. This collection of statements puts together an obvious problem in need of an engineered solution :

"Acceleration is the root cause of the difference (between actually riding outdoors on bicycles and indoors on trainers). Trainers model average power at constant speed and don't respond realistically to accelerations. So when you get up to sprint on a trainer, the pedal 'falls out from under you'. The acceleration of a trainer is wrong, wrong by as much as several orders of magnitude. After all, the mass of even a large-flywheel trainer is small compared to the mass of a rider."

Compton is now taking trainers one step forward with a cool add-on simulator that mimics real world riding conditions indoors.

How do you simulate real world conditions? It turns out that its all in the resistance force encountered at the pedals. Compton has designed a one package solution, called Pedal Force Simulator (PFS), through which riders can select a pre-programmed force simulator in a Palm device mounted on the handlebars. The simulation model is then communicated wireless to a computer at the rear wheel which then controls the pedaling resistance at about 1000 times per second.

The resistance computer of the PFS at the rear wheel

The PFS uses the standard validated model of forces acting on a rider to simulate instantaneous forces at the pedal. It measures acceleration and, using the standard model of forces acting on the rider and applies a resistive force at the pedals that is theoretically equal to the force a rider would feel riding outdoors under the simulated conditions (or theoretically sound). It does this using an eddy current brake that is electronically controlled by a computer in the resistance unit. The computer recalculates force at the pedals 1000 times per second so that the instantaneous force a rider feels at the pedal is always a theoretically correct force. [Source : Tom Compton]

Fig 2 : The display on the handlebars is a high-end Palm device with a large, color display area. Display software takes full advantage of the Palm device's capabilities. Displays and plots of parameters are provided. Workout data is saved to a sophisticated database. All measurement parameters normally expected are also provided. [Source]

The power of this system comes in customization and as said before, in mimicking outdoor variables. While there are pre-programmed courses in the simulator, a rider can also setup any ride profile he desires into the computer. Moreover, the PFS takes wind speed and direction as selected by the rider and transforms it in a way that gives realistic outdoor increases and decreases in wind speed which translates to a more realistic "windy" riding experience. As the wind is varied during the ride based on the model, the rider may feel necessary to shift into easier gears to pedal, just like in the real world.

After having built complete prototypes, all true and tested, Compton is now offering licensing of the technology.

In short, what is claimed by Compton is that the Pedal Force Simulator gets the instantaneous acceleration right. This affects the rider's ability to put power into the pedals and hence, captures real and subtle effects that one will never obtain on a trainer.

Thoughts and comments?

* * *

The AssBLEND® Bicycle Saddle

noreply@blogger.com (Ron) — Thu, 08 Oct 2009 04:49:00 +0000

Apologetic Design Technologies
Gentle Avenue, Koala Bear 73232

Dear Customer,

Congratulations. You've made the right decision in purchasing our newly designed bike saddle, the AssBLEND®.

We at Apologetic have heard your needs and bring you a product that meshes perfectly with your ass like a fine fitting coat, better than any other saddle on the market. Do away with ass hatchets that leave you with a feeling of being violated by a leathered cantilever.

To ensure you have the best experience with AssBLEND®, we will guide you through your first baby steps with it :

1. When you first bought the AssBLEND®, you should have obtained a big airtight box with the name AssBLEND® printed on it in shining gold. If this is not present, you have not bought our product and we suspect its a Chinese knockoff.

2. When you open our big airtight box in anticipation using the tabs on the side, you will find a lump of material in it about 3 inches in diameter sitting in one corner. It has a blueish tint to it and may seem like a moon rock. At the other corner, there should be a steel spatula. Right in the dead center, you should have been able to find this instruction sheet you read now, neatly folded and kept awaiting the grace of your eyes.

3. Where the bloody hell is the saddle, you'd snap impatiently. Ah. We expected exactly this question from our research. Patience now. Continue to step 4.

4. The blue lump/ball is pliable. Take it in your hand carefully. Feel the ball slowly. It is soft to touch. Yes feel it more. Ok, that's enough now...

5. This ball is a result of 5 years of research and design in our chemical laboratories at Apologetic. We have designed it in such a fine manner that it possesses a time dependent pliability for 5 min the moment it is exposed to atmospheric air at 14.5 psi.

6. Which means don't just stand there!

7. Please rush to the bathroom with the provided spatula immediately and strip off your trousers.

8. Close the toilet lid, place the ball on it at the dead center.

9. Now take a deep breath, try your best basketball jump and land right on the ball. Hold it there for exactly 20 minutes. The material is designed to work with human body temperature and hardens while expanding at the same time. While you wait, you can flip this instruction sheet in your hand for some testimonies from some of our customers. To give you comfort while you sit on the lump, we have made the testimonies (un)settling.

10. 20 minutes must have gone by now and you should feel something hard against the rear end. Take the provided spatula and scrape this hardened lump off your ass. Move onto step 11.

11. We forgot to say something in step 10. Please scrape it off carefully. That spatula is a work horse made by an artisan in South America so it can damage your ass with permanent marks if careless.

12. What you will observe on the spatula is a perfect negative of your rear end, containing an accurate description of all its crests and toughs, down to the most minutest details such as hair follicles, spores and childhood spank marks. Get your hands to work and do some additional shaping to get it into a saddle form.

One customer's sample has been provided below as reference.

Sample saddle in rough stages before processing

13. For final processing, what we call cold treatment, take any seatpost you would normally use, stick it into the AssBLEND® at the angle you desire and place into the your refrigerator.

14. After 1 hour of processing, what you should get is a rock solid copy of your ass attached to the seat post. Lock it in place on your seat tube with an allen wrench and off you go - yes, go...take your first ride with it.

Notice immediately as you ride, that every feature on your bottom melds into the AssBLEND® perfectly. What you've done is broken into the saddle with your ass in less than 2 hours. This is the AssBLEND® difference.

DISCLAIMER : Any product defect is not our liability. It's your own fault.

* * *

The G-G Diagram Applied To Bicycle Racing

noreply@blogger.com (Ron) — Mon, 05 Oct 2009 04:00:00 +0000

In the midst of our world of possibilities for data analysis in cycling performance, I was wondering if we could consider extending our scope a bit to other things.

As we speak, more models of GPS systems, power meters and heart rate monitors are being designed and released with are basically just different answers to the same old questions : "what's my speed", "what's my power", "what's my heart rate".

But what about other fundamental questions and problems imposed by bike racing? How could we explore and quantify those parameters?

As an illustration, one topic for discussion rarely brought to the table in our daily techno babble is that of acceleration and its impact on safety. Acceleration is an elementary concept in physics and we all know how important it can be towards team race strategies we see today in cycling. Is it getting the importance it may deserve from an analysis standpoint? I'm not sure.

The question is : Could an acceleration analysis be helpful to the racing cyclist and how?

Consider a human-bike system in an Individual Time Trial, a bike race against the clock on a circuit of predetermined length and design. Often in a race of professional caliber such as this, the standard deviation of the data set of results from the top 5 placers is mere seconds.

While time trials are usually steady power output races, if we considered a very technical race course with lots of curves and S-bends, we could say that a majority of the racer's effort is concentrated towards finding the optimum line between the bends while controlling the bike's speed through braking and acceleration. Miscalculations here could cost seconds and a possible podium spot.

Consider two racers, A and B, who chose different paths around a section of this hypothetical race course. Let's also say that they were riding bicycles of the same design, with the same handling qualities.

Fig 1 : Paths of two cyclists in a section of an ITT course. COG = center of gravity.

Who emerged faster at the right end of this section? Racer A or B?

Of course, we wouldn't know because we don't have enough information, you would say. The information missing here is that of the cyclists' acceleration.

To maintain a curved path on the ground, any vehicle, be it a bicycle or a Formula 1 race car, must be moving sideways as well as forward. Hence, there are two components to the bicycle's acceleration. They are :

1. Lateral or centripetal acceleration (LA), whose vector points towards the center of curvature of the road. A bicycle turns because of applied lateral tire forces. LA is affected by tire-road friction characteristics, angle of lean, square of the speed of the bike and radius of the curve, R. If lean is too large (i.e. rider tilts too much into the circle), centripetal force will be too much and the bike will start turning into a circle with radius smaller than R. If lean is not large enough, there won't be sufficient force to keep the bike on the circle and the bike will veer off, turning in a circle with radius larger than R.

2. Tangential or longitudinal acceleration (TA), whose vector points in the fore-aft direction of the bike rider. It is decided by pedal torque, aerodynamic drag forces, and traction limit of the tires.

If m is mass of bicycle-rider system, v its speed along the course, R the radius of curvature of the curve, t is time and g is the acceleration due to earth's gravity, then the above two are defined mathematically in terms of g-force as :

The vectors of these components and their resultant roughly look like this :

Fig 2 : The tangential and lateral vectors of acceleration represented graphically. A reversal of lateral acceleration vector (purple) signifies reversal of direction while a reversal in tangential acceleration vector (red) signified reversal of speed with time.

If we attached perpendicularly oriented accelerometers at the center of mass of the rider-bike system for the 2 riders in Fig 1 , and if we captured lateral acceleration (LA) and tangential acceleration (TA) through a data recording system, the data points when plotted on a graph could look like this (shown just for illustration, not to be taken for granted).

Fig 3 : This plot shows an example g-g diagram (a composite of friction c ircles for both wheels) for two bicycle riders on the same section of the race course on the same bicycle. It consists of a forward acceleration, turning and braking regions. Data points for each cyclist is shown in red and blue. A rough boundary envelopes these points for both riders. It must be noted that the g-g envelope/boundary for each of the cyclists is not fixed and depends on the bicycle, maximum tire friction force, human skill level and environmental conditions imposed on tire-road contact. This is the performance envelope for the bicycle-rider system. Outside this safe envelope, racing a bicycle could be dangerous.

This plot is called a g-g diagram. The concept was described extensively by aerospace engineer and race car driver Will Milliken Jr.

The difference in riding techniques of the two riders resulted in two different maneuverability boundaries, which can also be looked at as the maximum potential of the rider-bike system in any technical section of the race course for the race conditions. A given individual can only generate limited g's of acceleration to get up to speed. Theoretical limits of deceleration are on the order of 0.5g for a crouched rider on level ground before a person flies over the handlebars. If they are riding two different bicycles with different handling qualities and tires, the g-g boundaries will be different in this case too.

The ultimate limit of the g-g boundaries is imposed by the acceleration capability of the bicycle, which is primarily determined by the grip between the tire and road surface. This is represented in the g-g diagram by the outer oval shaped boundary.

When a racer sits down and studies his g-g performance, he could get a graphical picture of how he utilized the components of acceleration at specific sites on the course and how his choice of equipment may have cost him.

With appropriate software, answers could be generated to questions such as : What's the range of my accelerations? Which direction did I spend more time cornering to? Did I decelerate too much before the sharp curves? Did I accelerate optimally after the apex? How much emphasis did I place on acceleration and deceleration? Could I have changed the ratios of these accelerations by riding differently and emphasizing various body movements? How would these have affected or improved my course times at the end? What really caused my wipe out at that sharp bend and was it related to the lean angle and speed with which I faced that bend? How does all this change with a change in my bicycle tires? Or bicycle design.

How may this be specifically applied to improve performance? I have some thoughts :

1) The tire and the bicycle could be engineered to widen the g-g boundary as much as possible throughout an expected range of operating conditions (load, surface, temperature) without bringing about potentially dangerous modes of oscillatory motion.

2) The rider could train and improve his skill level to ride and exploit these maximal g-g limits of his machine.

Perhaps knowing the performance envelope of the bike being ridden for specific operating conditions may also empower the cyclist with a feeling for when he can safely take risks to win a race.

Take a look at the following two videos. One shows the capturing of the acceleration vectors on a g-g circle for a remotely controlled toy car. The one below it shows what looks to be a real time friction circle generation from a computer simulation.

Its inspiring to watch these data recording and software applications. Perhaps we could have a neat cyclocomputer in the future that could show the bicycle's g-g diagram in real time, if its practicalities have been established. Maybe cycling commentators will start talking about g-g diagrams and other cool things in future race telecasts. Who knows. What do you think?

ADDITIONAL RESOURCES :

The G-G Diagram
Rate Of Cycling Uphill Explained
Wild Ideas For New Cycling Products Part 1
Wild Ideas For New Cycling Products Part 2

* * *

Cold Forging Technology At Shimano

noreply@blogger.com (Ron) — Fri, 02 Oct 2009 05:25:00 +0000

If you read descriptions of Shimano's products, you'll often come across the words "cold forged aluminum", mentioned with great pride.

Forging is a metal shaping process in which a malleable metal part, known as a blank, billet or workpiece, is worked to a predetermined shape by one or more processes such as hammering, upsetting, pressing, rolling and so forth. Cold forming is a precision category of forging which does the same thing without heating of the material (room temperature), or removal of material.

Most of Shimano's products in the bike and fishing business utilize cold forming technology, which was established by the company more than four decades ago. It was in 1963 that Shimano introduced a cold forging plant to press precision parts for bicycles using dies and high pressure in order to form metal at room temperature. Plants such as these use presses, punches and dies that see very high working pressures, upto 1500 N/mm^2.

But why such specialized equipment?

The plasticity of aluminum at room temperature is low. The flow stress of aluminum decreases with increasing temperature. For alloys that are very easy to forge, such as 6061, there is nearly 50% decrease in flow stress between 700 deg F and 900 deg F.

Forgeability and forging temperatures of various aluminum alloys. Note that 810-900 deg F is the recommended forging temperature for 6061 alloy. Credits : Aluminum and Aluminum Alloys (ASM International)

Therefore, at room temperatures , because the flow stresses are higher, large machines capable of ramming and hammering the hell out of these alloys to get accurate shapes are needed. Of course, its more a delicate operation as opposed to the violence I have described above as great care has to be taken to prevent microscopic defects from developing in the cold forged piece, while it works at the upper limit of its strength.

On the other hand, because cold forging allows one to make parts without introducing the need for heat treatment and additional machining processes, it is an economical manufacturing method to produce precision, net-shape parts.

This is exactly what was needed by Shimano back in the day when it started designing integrated shift levers and gears that demanded high precision but which invariably suffered from the disadvantage of having a specialized and small market without much economy of scale. It has been mentioned that Shimano is one of the few companies in the world that can produce cold forged aluminum parts with close tolerances as those needed in the STI mechanism.

So how exactly did Shimano get around to having this precision, cost cutting technology? It turns out that the company has to thank a brilliant electrical engineer who basically re-created the entire company in the 1950's by helping it adopt the cold forging process, way before any other company in Japan at the time, even Toyota!!

Shuzo Matsumoto joined Shimano in 1954 with a dream. A graduate of the electrical engineering department of Osaka Prefecture University, he saw his mission as introducing cold forging technology to the replace hot forging then used. To achieve this goal, he was dispatched to the United States for 2.5 months by the company President, Shozaburo Shimano (died in 1958). In those days, only a limited amount of foreign currency could be taken out of Japan by any individual. Therefore, before departure, he was handed a lot of dollars obtained from the black market by Shozaburo and was simply instructed to "enjoy the trip".

The following snippet from page 76 of the book "Japan : Moving Towards A More Advanced Knowledge Economy, Vol. 2 Advanced Knowledge Creating Companies " describes briefly how Matsumoto went about accomplishing his mission of introducing cold forging technology to Shimano. Zoom in to enjoy the read. If you've anything else to share about Shimano and their production processes, give me a buzz.

ADDITIONAL RESOURCES :

Cold Forging In Bolt Production : A Video From Discovery Channel's How Its Made
Shuzo Matsumoto Patent : Rear Hub With Built-In Three Speed Change Mechanism For A Bicycle

* * *

Psychology Of Dog-Cyclist Encounters

noreply@blogger.com (Ron) — Tue, 29 Sep 2009 05:34:00 +0000

The human instinct to fear when something on four legs chases you down on a pathway is natural. The speed, ferocity and the sound of animal paws smacking the ground as it tries to catch up behind us sends us scrambling for escape responses. Getting caught up in this moment to save your own butt could be all too easy.

What about the dog? Are all cyclist-dog encounters dangerous for riders? This is the interesting question for today.

I have never had very troublesome dog encounters but I did have a few close ones which I managed perfectly fine by just increasing my velocity. That response wasn't hard to gather. I find it somewhat odd when people talk about carrying sticks of dog spray and other ammunition on their backs as if preparing for some kind of surprise ambush like those between highwaymen and money wagons in western movies.

Maybe you'd have a different perspective and we can surely disagree.

In this post, we take a look at the ingredient of dog sprays and then try to understand the mind of a dog during a dog chase. We think we know animals, but we might actually be surprised by how much we don't. What's the source of the dog chase and what's the best course of action from a cyclist? Read on...

DOG SPRAY AND ITS SHU VALUE

Its become a sort of fashion these days to go with the "Point and Spray" method without a furnishing a second thought. Besides giving the user of the spray an inflated sense of security, there's probably some degree of thrill involved in knowing that you'll be spraying nasty crap into someone's eyes. I did wonder a few times whether people stop and think about what this crap really is.

Bite into a piece of hot pepper and one quickly realizes the complex reactions involved in the body to flush out this irritant heat. If that's not enough for you, try some of the interesting hot sauces out there. People make a living through marketing this stuff and gaining notoriety for the "heat in the bottle". The more, the better.

I was once offered a bloody little drop of Dave's Insanity Sauce to try as relish by a friend. Just a tiny drop about 0.5 inches in diameter on the palm of my hand.

How did it go? Well, let's say I was too saucy in my overconfidence to begin with. The moment the wretched stuff hit my tongue, my eyes started watering streams and my throat, mouth and ears felt like they were lit on fire by a propane torch. Wow. Its relieving to just say that it was something I tried, in past tense.

You'd think this is the hottest stuff around that you had in your mouth but the gurus of spice will wave you off and tell you otherwise. For perspective, inspect the table below. This gives the Scoville Rating, which is basically the piquancy spectrum, for peppers. The unit of measurement is Scoville Heat Unit or SHU for short.

The Scoville Scale of peppers. Click to zoom.

The predominant ingredient in dog spray is oleoresin capsicum (OC). Take your canister and inspect it. It might even say something like "contains capsaicin and capsaicinoids", which is true as the extracts of OC contain capsaicin. Capsaicin causes neurogenic inflammation.

The hotness of OC is directly related to the amount of capsaicin in it, which varies significantly from manufacturer to manufacturer. The more capsaicin content the OC has, the hotter and more effective the spray will be.

While Dave's Insanity Sauce has about 250,000 to 500,000 SHU's, commercial grade self-defense sprays such as dog spray, mace and pepper spray have a minimum of 2 million SHU's and beyond. That's 4 to 8 times the strength of Insanity Sauce.

Now imagine if someone who didn't like you took the same Insanity Sauce and squirted a bit in your eyes. Good luck, my friend. You may see your bum through your head.

When you spray 2 million SHU's or more on someone's face, into their nose and eyes, you bet its going to hurt real bad. Humans could easily get help and get nursed with water in the event this happens. What's a blinded dog to do in the middle of the road? I'm not sure.

PSYCHOLOGY BEHIND THE DOG CHASE

Many times I have wondered what causes a dog to chase a cyclist. What's the motivating factor for ticking a well domesticated animal, sending it scuttling behind something else it spotted on the road? What's the psychology of a dog's mind during this scenario?

I don't profess to be a dog expert. That's why I posed this troubling question to Alexandra Horowitz, a famous professor of psychology and cognitive scientist with Barnard College. She's probably one of the few in the U.S who leads a dog cognition lab which studies dog behavior.

Her recent book, Inside of a Dog: What Dogs See, Smell, and Know, describes recent discoveries of the fields of dog cognition, behavior, and biology in order to better imagine what it is like to be a dog. Just last week, her work was featured in a well written article in Time Magazine titled The Secrets Inside Your Dog's Mind.

Since she understands dogs better than most of us, I asked her to unravel for me the psychology behind the dog chase, from the dog's perspective. She was, in a way, the perfect person to ask because apart from being a scientist, she also happens to be a runner and recreational cyclist.

Ms. Horowitz's best explanation to me went along these lines. Consider the visual system of dogs. The visual system of canids evolved over the course of many years to notice quick movements, like fleeing prey.

As hunters, dogs and their forebears developed a very high sensitivity to motion, dogs became much quicker to notice a small motion in their peripheral vision than we are. This is adaptive for an animal which chases moving prey.

Not all dogs chase bikes, of course. But for those that do, they see the smooth, quick motion of the bike and it triggers their prey instinct to chase the "animal". In our case, the "animal" to the dog is the cyclist. The cyclist is the source of the problem.

She also pointed out to me that this isn't the same as saying dogs see cyclists or runners as "prey" because after all, they never consume you as you dismount. But they do get very excited and their nervous system just riles up for the chase.

What would her approach be as a cyclist? The best way to stop a dog is to simply stop the illusion of the prey, i.e, stop the bike. A dog may still bark and stay riled up, but does this only for a short time, as their nervous energy subsides. It may be impractical to stop if you're on a long ride, but keep in mind that the dog is just excited and can be calmed by stopping the bicycle.

Of course, this is easier said than done as this seems a counter-intuitive step for a majority of us. But since the dog psychology in dog-cyclist encounters makes sense, the response from a cyclist countering exactly that psychology may also make sense.

I also asked her if owners could train their dogs in such a way that they learn not to do what their instinct tells them to do on seeing a cyclist on the road. According to her, the training itself might be intensive, but something like this is certainly possible. A dog can be trained to notice, but not act on these cues. Unless an owner specifically trains their dog to be still when a bike comes by, it is not something dogs with this visual tendency will do on their own.

Ms. Horowitz believes, like I would also like to, that in most case scenarios, there is no pressing need to spray a dog with a canister of a million SHU's. In fact, she believes this could really up the ante and "cause" a secondary response in the animal.

Do you have a dog chase story to share? What are your thoughts on dog behavior? Please join the discussion if you know you have specific experience as a cyclist, dog owner or as researcher involved in animal behavior.

ADDITIONAL READING :

Guide To Chile Heat
Health Hazards Of Pepper Spray
Scoville Scale Chart For Hot Sauce And Hot Peppers
The Secrets Inside Your Dog's Mind (Time Magazine, 21 September 2009)

* * *

Saturday Stupidity VI

noreply@blogger.com (Ron) — Sat, 26 Sep 2009 05:57:00 +0000

Laugh the weekend away for me, will ya?....

By the way, Cozy Beehive has officially chosen the following piece as its soundtrack. Let's apply it to bicycles. I'm already dancing. Can you keep up?

FOR PREVIOUS INSTALLMENTS OF STUPIDITY, SEE :

Saturday Stupidity I
Saturday Stupidity II
Saturday Stupidity III
Saturday Stupidity IV
Saturday Stupidity V

* * *

The Highlander Cycle Tour

noreply@blogger.com (Ron) — Thu, 24 Sep 2009 04:01:00 +0000

Distance : 105 miles (170km)
Total Vertical Climbing : 10,000 feet+ (3050 m)
Weather : 56 Deg F, Foggy With Rain (13 deg C)
Ride Time : 8.5 Hours

In between these days thinking about bicycle dynamics and other personal affairs, I managed to pull myself together and ride the one and only Highlander Century on September 12.

The organizers of the Tour call it the King of the East, desiring to put it close to strenuous rides in the U.S such as the Triple Bypass in Colorado (120 miles, 11,140 ft climbing) and California's Death Rid e (129 miles, 15000 ft climbing).

Held in the stunning region of the Finger Lakes (NY's answer to the Napa Valley in CA), the riders who participate in this marquee event of the weekend visit 5 beautiful lakes and climb all the hills separating them. Featuring more than 10,000 feet of total climbing in 18 separate climbs, 40% of these climbs are 1-2 miles long with grades ranging between 9-23%. Fabled climbs such as "Le Grand Egypt", "Mont. Ste. Millers", the now legendary steeps (23% grade) of Le Alpe de Bopple and the Col de Gannett, are all Highlander staples.

The following is a 15 min Google Earth video essay of the 2009 Highlander route that I prepared for you, with relevant details of aid stations, climbs and regions visited. The music captures the drama and difficulty of this ride, yet it does look much easier from the sky. Note that you can view the same on Youtube, broken in two parts, and in slightly higher quality. See : Part 1 and Part 2.

The Highlander Century : A Google Earth Essay from Ron George on Vimeo.

The route for this year had lots of character in both paved and graveled roads. The weather imposed a necessity of fine bike handling skills while using the gravel paths. The cold was constant and the foggy, rain mist was periodic and made for reduced sight. Sweat saturated the helmet lining and emulsified with rain making it slightly more harder on sight. Multiple flats had us stopping many times to change tubes in wet weather. I mean, there really is no way to keep these variables at bay.

6 aid stations keep you loaded with well-needed food and liquid supplies. Its also a time for conversations about routes and cramps and hills gone and hills to come. The psychological factor can grab your head like a scorpion if you're a newcomer here. Sometimes, its better to stop listening to people's conversations.

The ride was a great test of fitness and challenge to me. Instead of talking about myself, I would like to say a few things to those who are willing to face challenging rides such as these :

1) Carry extra food that you are familiar with. You don't get too many electrolytes at the aid stations so have something of that nature with you. I gave up on crappy race gels long ago. For relentless periodic climbing, I take glucose tablets.

2) Find a friendly group beforehand to ride your tour with. Maintain a sense of humor through challenges. This is hard as it is already. And always lend a helping hand to someone stuck out on the road in the middle of nowhere with equipment issues.

3) Come prepared to ride by having lots of miles in the legs. If you don't have time to train, the least you can do is practice plenty of hill repeats. I rode 4 centuries in the summer for fun and did rake some serious mileage and climbing in the Green Mountains of Vermont earlier this year.

4) Pay close attention to your core strength and conditioning before attempting a ride such as this. In a ride that features 10,000+ feet of climbing, you'll quickly come to realize why you climb only partly with the legs. Most of your power comes from the torso, especially the lower back. Weak muscles in this region can seize up pretty quickly and your experience climbing relentless hills will be extremely painful. If something of this nature does pop up, get off the bike and stretch.

5) Never, ever attack hills if you don't know what you're doing. Give them the respect they desire, or they'll topple you upside down. Its like dealing with a black mamba. Breathe from the belly and stay relaxed on the bike. This isn't a race.

6) On steep roads of more than 20% grade such as Bopple, its more energy efficient, but slower to cut across the hill in a zigzag path. If you can't do that either, its better to walk but do that knowing its hard to gain momentum to climb back on the bike again.

Here are some few pictures I captured from aboard my Colnago C40. I hope you like them, although they don't do much justice to the understanding of this ride. Enjoy and do ask questions if you have any!

Come ride this beast and be a Highlander! Are you game?

Rollout from start at 8am

Gannett Hill

Gravelled road

Aid station 1

Aid station 2

Pinewood

Gullick to Mosher Hill

Egypt Valley

Bristol

Lake Canandaigua

Final climb up Bopple Hill

Jubilous Highlanders at the finish after dinner (me in the center in white)

ADDITIONAL READING :

Highlander Cycle Tour Official Website
Tour of The Highlands (more on Bopple & Mosher Hills)
Democrat&Chronicle : Highland Cycle Tour has been drawing cyclists to Ontario County hills for 10 years (Sept 10,2009)
Visit Finger Lakes NY

* * *

Dynamic Stability Of Bicycle Design : Part 4

noreply@blogger.com (Ron) — Tue, 22 Sep 2009 06:05:00 +0000

"Trail can be found by supporting the bike on a flat surface in an upright position for measuring purposes. A centerline is run down through the head tube until it hits the flat surface. A vertical line is then dropped from the front axle until it hits the ground. The distance between these two points on the ground is the trail. The comfort range of trail is 50 to 65 millimeters. Beyond these limits in either direction, it would be considered less desirable."

- A quote from Chapter 1 : Frame Geometry, The Paterek Manual for Bicycle Frame builders

Question : Why do we know what we know about the comfortable range of bicycle design parameters and ride desirability? How do we know it? Can such claims be applicable to all bikes with any rider in general? What does science say about these statements?

Continued from Part 4

In the previous post, I presented a mathematical bicycle model to you (validated by research) and a computer program called JBike6 that uses this model to calculate the bicycle's stability eigenvalues. We also explored an important point that this model is, regardless of complexity, still simple in terms of being a riderless model not accounting for the frictional properties of the tires. Hence, whatever results you see in the JBike6 is only so true as long as you consider a riderless bike with other simplifying assumptions established.

Interestingly, Jim Papadopoulos (thanks Jim!) pointed out to me in a comment to the previous post that in terms of ridden bikes, he surmises that JBike6 might apply best to recumbents (where the rider is secured to a seat) with extremely hard tires, ridden no-hands. So its applicability is not lost.

So what is the bottom line of all this mess? What I've been trying to convey to you through this series is that studying a bicycle is a difficult and complex task. The bicycle really is a complex vehicle. Why do we know what we know about the bicycle dynamics, and how do we know it?

Some of us like to think we know bicycles and like to give out general rules of thumb for design so as to get a self-stable bike. Now this could be true for the particular bike design being considered but the point is, it may not be true for different designs and different people. A different bicycle with a differently sized rider can have totally different dynamics.

Hence, it turns out that when someone makes general claims about bicycle design that he thinks he or she knows will work for all bicycles, that's just an unvalidated statement in a true scientific sense. They're what's called an anecdote. Anecdotes come through hearsay or someone's personal experience with building something. However, the state of the art in bicycle science has yet to concretely come out with the unifying principles behind why a rider controlled bicycle, any bicycle, behaves the way it does.

Science has a long way to go before establishing the truth behind general statements about parameter changes and their effect on ride characteristics as applicable to all bicycles of any design. Science also has some ways to go in studying complex modes of motion in bicycles that we talked about in Part 2, particularly the dangerous ones such as high speed wobble that can bring harm and loss of property to the owner.

While I leave you with these thoughts, I'd like to present some research by one of my readers, Jason Moore. Jason is working towards his Phd in Mechanical and Aerospace Engineering at UC Davis. He's currently a Fulbright Visiting Scholar and Researcher at the Bicycle Dynamics Laboratory at Delft University.

Jason and his advisor, Prof. Mont Hubbard, employed the same validated bicycle model we've been talking about and studied the dynamics for the design parameters of an old Schwinn bike he owns. The model was then used with a physical parameter generation algorithm to evaluate the dependence of four important design parameters on the self-stability of a bicycle. These parameters were :

1) Front wheel diameter

2) Head tube angle

3) Trail

4) Wheelbase

In the end, the duo were able to generate interesting results through graphs that showed how changing the above four parameters independent of each other affected bicycle stability in weave and capsize critical velocities.

Their research paper was featured in Engineering of Sport, the journal of the International Sports Engineering Association. The graphs show definite parametric dependence of bicycle stability. Most interestingly, their results disagree with the general claims made by the Paterek (shown at the beginning of the post) about the comfortable limits of trail by showing an increasing stable speed range with increase in trail, provided this increases was kept within reasonable limits.

With Jason's permission, attached below are 8 pages of the paper titled Parametric Study of Bicycle Stability. Please click on them to expand and read. This is also available to read via Google Books Online. See this link.

Finally, if you have any questions about bicycle stability that bothers you, please ask away and I guarantee you'll receive an adequate reply from Jason, Arend Schwab or Jim Papadopoulos, as they all read this blog.

Thanks for sticking along on this journey!

* * *

The Engineering of Sport 7 : Proceedings of the 7th International Sports Engineering Association Conference. Biarritz, France. June 2-6, 2008.

CONNECTED READING :

Dynamic Stability Of Bicycle Design : Part 1
Dynamic Stability Of Bicycle Design : Part 2
Dynamic Stability Of Bicycle Design : Part 3
Dynamic Stability Of Bicycle Design : Part 4
A Bicycle Model To End All Models
"Linearized Dynamics Equations For The Balance & Steer Of a Bicycle" - J. P. Meijaard, Jim M. Papadopoulos, Andy Ruina, A. L. Schwab, 2007
History Of Bicycle Dynamics

* * *

Dynamic Stability Of Bicycle Design : Part 3

noreply@blogger.com (Ron) — Fri, 18 Sep 2009 04:14:00 +0000

Continued from Part 2.

Hello bike nerds! Before you engage yourself in another installment in my series on bicycle stability, have a look at this clip from The Daily Planet shown on Discovery Channel Canada. The individual interviewed is Arend Schwab, a mechanical engineer with Delft University of Technology.

Modeling For Stability Analysis

The bicycle is a complex system to analyze. In Part 2, we talked a little about modeling the idealized passive rider-bicycle system, simplifying many things through assumptions but still capturing enough detail to go ahead with a reasonable analysis. The full analysis, particularly that involving the derivation of the equations of motion, is beyond the scope of this blog.

But to put it in simple words, what the analysis yields are two coupled second order, non-linear, differential equations in lean and steer. Then, these equations are linearized through a carefully followed algorithm to give us an eigenvalue problem. The eigenvalues gained from the characteristic equation help us assess the stability of the modes of bicycle motion. Eigenvalues are the cool numbers that give us an idea of the stability of the engineered system when the system is disturbed.

Fig 3 : What eigenvalues tell us about stability. To make an engineered system stable, we're all interested in attaining negative real numbers for eigenvalues. Stable motion of a bicycle has negative, real, eigenvalues. Courtesy : University of Michigan, Dynamics And Controls

Many years of research has allowed us to understand the nature of the bicycle's linearized equation of motion (LEOM). The LEOM, expressed in terms of small changes in the lateral degrees of freedom being the rear frame, roll angle ф and the steering angle δ, from upright straight ahead configuration at a forward speed v, looks like this in matrix form :

Fig 4 : LEOM Of A Bicycle

where

M = symmetric mass matrix which gives the kinetic energy of bicycle system at 0 forward speed
C1 = damping matrix, proportional to forward speed v
K0 = first component of stiffness matrix, which when combined with 'g' yields a symmetric quantity proportional to gravitational acceleration and can be used to calculate changes in potential energy
K2 = second component of stiffness matrix, which when combined with the square of forward speed, v, gives a quadratic quantity in forward speed and is due to centrifugal effects.
f = applied forces

Consider each of these matrices as packages and the contents of these packages would be specific combinations of the bicycle's design parameters shown in Fig 2 of Part 2. To know what goes where in these matrices, you need to read this paper from Delft.

Finally, the time varying variables in the LEOM are :

Fig 5

ф = roll angle
δ = steering angle
Tф = action-reaction roll moment between fixed space and rear frame due to external causes like wind or lateral pushing force from behind.
Tδ = action-reaction steering moment, torqued by rider's hands.

Because we're analyzing a passive, uncontrolled bicycle, both these moments are taken to be 0. The characteristic equation is then the determinant of the equation in Fig 4 which gives us the eigenvalues of the problem. Eigenvalues are the exponential part of the solution to the differential equations of motion and as said before, help in stability analysis.

Computer Program To Plot Eigenvalues

Solving all this by hand takes pages of tedious work. If we can program these rules into a computer, it can quickly solve the characteristic equation. The input for the program would be all the bicycle's design parameters. The output would be the eigenvalues. We can even tell the computer to plot them for us as a function of forward speed v, for any particular bicycle configuration that we provide.

That's exactly what JBike6 does. It is a program written in MATLAB, a collaborated work between Delft University of Technology and Cornell. For small values of steer and lean, the program is perfectly accurate. Jim Papadopoulos, a contributor to JBike6, is also the co-author of the book, Bicycling Science (I had interviewed the main author, Prof. David Gordon Wilson from MIT earlier this year).

As the main illustration for today, I pull up an example bike, already provided in the program. It is a Litespeed Ultimate bicycle and Fig 7 shows its design parameters, all values in metric units.

Fig 6 : Litespeed Ultimate

Fig 7 : Litespeed Ultimate's 25+ design parameters entered as inputs to program. Click to zoom in.

After checking these boxes, I hit the calculate button on the upper right hand side. The program solves the linearized eigenvalue problem and gives me 4 generalized eigenvalues. It plots these values on the y-axis as a function of forward speed, v on the x-axis.

Fig 8 : Litespeed Ultimate's eigenvalues vs forward speed. Re = Real, Im = Imaginary

The above plot tells me something about the stability of this bicycle as a function of speed. To understand what's going on, let us remember the information about eigenvalues in Fig 3 and commit it to mind, or go back and refer to it. Now read the plot in Fig 8 slowly from left to right in the order of increasing speed v. We'll take it piece by piece.

Speed Range Of Interest : 0-0.5 m/s (0-1.118 mph)
Motion: Capsize
Nature : Stable, non-oscillatory capsize

What would you expect from a bike standing still or nearly so? It will simply flop over. How do we know this? The fact that the plot yielded large positive eigenvalues or real numbers tells us right away that this is a very unstable motion. Two positive and negative pairs of roots correspond to both falling and uprighting of the bicycle. One pair corresponds to when the steering is turning toward the lean; the other when it is turning opposite to lean. Since there are no imaginary parts of eigenvalues, it tells us that this capsize motion is non-oscillating, like I mentioned in Part 2.

Speed Of Interest : 0.5-1 m/s (1.118-2.237 mph)
Motion: Transition to weave
Nature : Unstable, oscillatory weave with stable capsize

As the forward speed v is increased from 0.5m/s to slightly more, two real eigenvalues (in blue) become identical, coalesce and form a conjugated pair, which is where oscillatory weave motion actually shows its face. In this oscillation, the bicycle sways about the headed direction.

Speed Range Of Interest : 1-4.8539 m/s (2.237-10.858 mph)
Motion: Weave+Capsize
Nature : Transition to stable weave, with stable capsize and oscillation

The positive eigenvalues tend to decrease in magnitude, so the motion is tending towards stability. Eigenvalues with imaginary parts lead to oscillation with increasing frequency, and the rate of increase is rapid at first, but then slows. The bike will weave back and forth one or more times before falling over.

Speed Range Of Interest : 4.8539 m/s (10.858 mph)
Motion: Weave + Capsize
Nature : Weave speed critical point, with stable capsize

Weave speed is that speed at which weave does not grow or decay, as can be seen by the eigenvalue crossing 0. Hence, weave speed is 4.8539 m/s. It is stable and forms the lower stability range bound for this bicycle. Eigenvalues corresponding to imaginary parts is oscillating motion. Beyond this point, weave is stable until infinity.

Speed Range Of Interest : 4.8539-7.0994 m/s (10.858-15.880 mph)
Motion: Weave + Capsize
Nature : Asymptotically stable behavior

This speed range is the stable range for the bicycle, as the eigenvalues corresponding to both weave and capsize have no positive numbers. The bike will weave back and forth, less so each time, and eventually roll straight ahead, although not necessarily in the original direction.

Speed Range Of Interest : 7.0994 m/s (15.880 mph)
Motion: Weave + Capsize
Nature : Capsize speed critical point, with stable weave

Capsize speed is that speed at which capsize does not grow or decay, as can be seen by the eigenvalue which is at 0. Hence, capsize speed is 4.8539 m/s. It forms the upper stability range bound for this bicycle. Crossing this point gets us over the stable range.

Speed Range Of Interest : Greater than 7.0994m/s (v>15.880 mph)
Motion: Weave + Capsize
Nature : Stable weave with unstable capsize

Small positive eigenvalue for capsize gets it into unstable mode. Eigenvalues with imaginary parts, but whose real component is much smaller than the positive eigenvalue overwhelms oscillations. The bike slowly leans farther and farther to one side, without oscillation, until it finally falls over.

Thus, stable speed range for an uncontrolled Litespeed Ultimate is between 10.858-15.880 mph, but for all practical purposes, we could say it becomes easily balanced above 2 m/s. One important thing to realize is that capsize instability in these regions is very slow and thus can be easily corrected by a controlling rider. Also note that all this time, we have deliberately avoided talking about wobble. Wobble is complex and cannot be described without analyzing tire dynamics. This is an on-going study in bicycle dynamics.

In the final series to come shortly, I'll show you a cool peice of literature one of my readers has authored from which we might be able to study how changing the parameters in bicycle design affects the modes of bicycle motion. Now you can all take a deep sigh and have a good weekend.

CONNECTED READING :

* * *

Dynamic Stability Of Bicycle Design : Part 2

noreply@blogger.com (Ron) — Mon, 14 Sep 2009 04:01:00 +0000

Continued from Part 1.

Here, we'll study some fundamental concepts associated with bicycle motion, before we step into play mode. This is necessary for understanding what is to follow in later parts.

A bicycle is a single track vehicle and its dynamics can be studied with or without a rider. For purposes of our discussion here, we consider the human to be passive, rigidly attached to the rear frame of the bicycle, providing no control feedback whatsoever.

Fig 1 : A diagram of the model. Courtesy : Koojiman et.al

Engineers and scientists love to make models to study behaviors of systems. And it turns out that we can go ahead and make a mathematical model (see above) of the bicycle with a rear frame, a front frame with handlebars, and finally two wheels. Certain assumptions are made in the process, such as frictionless revolute joints, non-slipping rolling contacts for tires and knife-edge wheels.

Researches such as Francis Whipple and others have done this for almost a century, hence we stand on the shoulders of giants. The state of the art in bicycle dynamics also adopts the model and the linearized analysis behind it happens to be experimentally verified to justify the assumptions made in creating the model.

After introducing non-holonomic rolling and kinematic constraints, the typical 24 dimensional bicycle can be reduced to 3 to represent its configuration space. These are :

1) The roll rate of the rear frame, ф* (phi dot)
2) The steering rate, δ* (delta dot)
3) The angular rate of the rear wheel relative to the rear frame, θ* (theta dot)

Just imagine how complex analyzing bicycle dynamics in 3 dimensions is , leave alone analyzing it as a 24 dimensional system.

As it turns out, the state of the art model of the bicycle has 25 different design parameters, like the real world bicycle. These are shown in the graphic below. Just count the tick marks as you go along.

Fig 2 : Parameters affecting bicycle motion

Here, we get an idea of the different things that affect bicycle design. Its not just trail, or this angle, or that length, or this mass, but a picture bigger than that. Moreover, we can infer that there is an inter dependability among parameters. For example, changing the moment of inertia of your bicycle wheel is likely to change its mass as well.

In terms of their physical significance, single track vehicles possess 3 main modes of motion. There are precise scientific terms for these modes and its important that one doesn't muddle up their definitions and meanings.

1. CAPSIZE

Capsize mode is a non-oscillatory behavior involving both roll and steer and its prominence depends, among others, on the bicycle's speed and deceleration of the bike. The forward speed at which capsize motion neither grows nor decays is called capsize speed.

Basically, the mode tells you when the bicycle will lean over and fall and how easily it will do this. A bicycle without a rider at very low speed is unstable in roll and will simply fall to the ground laterally after moving into a tightening progressive spiral, sort of like a broomstick upon the action of gravity. A rider with some basic skills can easily stabilize this mode.

If a bicycle is rapidly decelerated by locking up the front wheel, it could capsize. In cornering at higher speeds, the ease with which capsize occurs (if you would consider it a rider controlled capsize) determines the cornering maneuverability of the bike. If capsize mode has a lesser time constant (less falling time), you can lean into turns and execute curves a little more correctly. So the lesser the falling time, the more unstable is this capsize mode.

Thus, we see how taking some stability away from the bike affords maneuverability. An overly stable bike is sluggish to control. Its not very responsive.

2. WEAVE

Weave is a complex, oscillatory behavior, 2-3 Hz in frequency, in which the bicycle oscillates or steers sinuously around the axis of the ground in the headed direction. The forward speed at which this oscillatory motion neither grows nor decays is called weave speed. This, although separate from the idea of the high speed shimmy or wobble cyclists always talk about, has a component of wobble in it that it is difficult to say which is which. These two modes are associated with each other in reality, although we like to think of them as separate.

Here's a video demonstration of weave I obtained from the net :

3. WOBBLE

Wobble is an unstable, oscillatory, steering motion. It can also be called steering oscillation. In popular literature, it is called Shimmy, a word that originates from an American dance style in the 1920's.

Here's a video demonstration of wobble. Use it to differentiate from weave.

From observations and anecdotal evidence, it is widely agreed that this mode occurs at some low speeds (see weave above) and also comes into play at some critically high speeds when frequencies are rapid from 5-9 Hz in range. To put things into perspective, a baby being rocked to sleep is at about 1 Hz. 9 Hz or more is rapid and dangerous and can quickly lead to a loss of control unless the rider consciously reverses the negative damping through body movements or braking.

The problem with rider provided damping is that sometimes, high speed wobble can be so quickly induced by some external disturbance that it takes the unassuming rider by surprise. This disturbance could arise from an irregularity on the road, or a bad mass of air, such as the wake turbulence from a box truck passing a cyclist on a descent. This initial condition could become large quickly before the rider can even react appropriately. The self-excited growth of this oscillation could lead to catastrophe.

From decades of detailed studies in motorcycle and airplane wobbles, researchers have agreed that a study of high speed shimmy is one involving the study of the elasticity of the steering head and frame and the complex interactions that come into play at the tire-ground interface.

When someone tells you that your loose bearings are what's causing the shimmy and you are completely sure that there are no loose bearings after periodic inspections, its time to expand your curiosity to the flexibility of the front end of the bike as well as the type and condition of the tyre you're using.

Almost all vehicles have the shimmy problem. It seems to be one of the engineering challenges in transport. A well designed bicycle is one in which the natural frequency of wobble is well above the speeds at which people normally travel on a bicycle. But meeting this is a challenge as bicyclists often like to mix and match different products and components while building bikes. Perhaps it would be wiser on the cyclist's part to keep the idea of a restricted speed range in mind while enjoying high speeds.

At this point, I'd like to shift your attention to the topic of this series. It is bicycle stability. In the next post, we will look at the bicycle parameters of our state of the art model and see how changing the values of the bicycle's parameters as shown in Fig 2 influence dynamic stability.

Keep the cup of your favorite beverage ready. And the rubber side down.

CONNECTED READING :

Dynamic Stability Of Bicycle Design : Part 1
Dynamic Stability Of Bicycle Design : Part 2
Dynamic Stability Of Bicycle Design : Part 3
Dynamic Stability Of Bicycle Design : Part 4
"Bicycle Dynamics", Experiences Blogged By Engineer Jason Moore
"Linearized Dynamics Equations For The Balance & Steer Of a Bicycle" - J. P. Meijaard, Jim M. Papadopoulos, Andy Ruina, A. L. Schwab, 2007
History Of Bicycle Dynamics

* * *

Dynamic Stability Of Bicycle Design : Part 1

noreply@blogger.com (Ron) — Wed, 09 Sep 2009 15:40:00 +0000

Bicycle motion is more complex than you think, perhaps more than that of an automobile. When someone, such as a frame builder Mr. X, Y or Z, tells you that one or two design parameters alone influence the ride of your bike, all they're providing you with is a half baked cookie, if not inexperienced advice.

There is more to bike design than drawing a colorful sketch of it on CAD. Wouldn't you want to know the big picture? How do different bicycle designs affect bicycle stability? How does changing this parameter or that parameter affect bicycle stability?

By the way, what is stability? Take a bicycle. Will it stand by itself? No. It is statically unstable. We can also be cool and call it neutral static instability. Now ride the bike, slowly increasing speed. At low speeds, you find yourself oscillating, trying to control the bike. When the bicycle attains a certain speed, it takes lesser effort and skill to keep it moving in a straight line.

Now what if one of two things happen?

1) The bicycle encounters a external disturbance to straight line motion while moving, resulting in an oscillation.

2) The rider gives an unnecessary input to the bicycle while in motion, resulting in oscillation.

Now will the bicycle design be such that it dampens (kills) the oscillation as a transient response or will the design be such that the disturbance gives rise to an unbounded, dangerous motion?

If the disturbance will be dampened, how soon will it be dampened and how soon will it return the bicycle-rider system to steady state equilibrium? If the oscillation does not die out quickly enough, someone could potentially get hurt and expensive property could be damaged (think a crash in a fast moving group of riders). So how quick is quick enough? Is it 2 ms, 2 hours, 2 weeks?

The above are important questions in dynamic stability analysis. Stability is the most important concept in the world. I will take the liberty to say that. If a phenomenon were not stable, we could hardly observe it, understand it or study it. If sunlight wasn't stable, forget life. If there's an earthquake every minute on our planet, forget trying to do any useful work. Insanity in a human being is instability. So thank the heavens for our stable world where it matters most.

Likewise, all engineered systems have to be stable. If that wasn't the case, we would hardly fly from one continent to another and see new countries, meet new people. We would hardly stay on the right orbit and reach the moon, landing a few proud men on it. If designers couldn't build a stable Ferrari F1 car for Schumacher, he wouldn't have won any fancy accolades and may have remained poor like the most of us.

A bicycle is statically unstable by nature but it takes something to change its behavior such that it becomes stable and does useful work for us. For transport oriented designs, especially in busy urban areas, it is favorable that the bicycle doesn't take too much skill to become stable. If it does take high speeds and skills to ride such bicycles in such busy areas, no one is going to bother bicycling. Someone could get hurt, leave alone the attainment of a deep dissatisfaction with the whole experience.

Designing and engineering a good bicycle for specific applications is paramount in asking people to get on bikes and use them to save our environment. Especially if these people have never had or lost touch with the skill needed to ride a bicycle.

We'll look at bicycle stability in depth in Part 2 of this series, which you can read here.

Before you leave, watch the following video from UND Aerospace. The subject of the video is an airplane, but it still does not diminish the importance of stability in all engineered systems. Let's learn!

Principles Of Stability on Howcast

CONNECTED READING :

Dynamic Stability Of Bicycle Design : Part 1
Dynamic Stability Of Bicycle Design : Part 2
Dynamic Stability Of Bicycle Design : Part 3
Dynamic Stability Of Bicycle Design : Part 4

* * *

Discuss : Contemporary Body Culture In Cycling

noreply@blogger.com (Ron) — Mon, 07 Sep 2009 07:39:00 +0000

Anthropology of sport is an emerging research area for Dr. Brian Joseph Gilley of the University of Vermont. His research narrows in on the ways body culture in professional road cycling articulates with transnational sporting tradition and business. In particular, he is concentrating on the surveillance of bodily movement (inspired by the work of Henning Eichberg, a famous cultural sociologist) by the cycling sports industry. This research includes investigations into the ways cyclists manage their bodies and the ways specific forms of bodily movement are endorsed by the cycling sports industry (fortunately or unfortunately).

Attached below are 4 pages from a paper of Dr. Gilley's focusing in on the culture of the cycling sport. Titled Cyclist Subjectivity: Corporeal Management And The Inscription Of Suffering, it suggests that to deconstruct cycling discourse is to reveal the mechanisms of an unquestioned set of values governing individual bodies. Dr. Gilley seeks to answer where these values came from and highlights a picture for us where the political economy of cycling and techniques of corporeal management are all surrounded on one thing - the individual cyclist's body.

After you have finished reading, you can engage in a discussion here with me on issues of the body culture in our sport. This is an interesting topic and some questions ring in my mind for you people across the world. Questions such as the following :

Has our "established" values and systems of cycling body culture (that you see on TV, read about, or hear from other people) forced you to do some things with your body that you would otherwise not have done had you not been a cyclist?

Have you been pressured to dope? Have you starved yourself or lost an unhealthy amount of weight to stay with the weekend group ride or gain that addition in your power to weight ratio? Have you lost out in a relationship where your partner wouldn't accept you spending so much time and energy training, and on top of it all, looking gaunt and weary in parties and other social events because of this training? Do you think there's a stigma in your country or culture around "thin" because "thin" is considered inferior? Have you lost a job because your boss thought you look unhealthy and not suited for the task and you reached that state due to your cycling activities? Are you always in the widely popular mindset of "ride strong, ride fast, take risks" that you get yourself involved in unnecessary crashes and injuries which, of course, risk your health?

C'mon, let's talk! Anything is possible on this blog!

Page 1 : Click to Zoom

Page 2 : Click to Zoom

Page 3 : Click to Zoom

Page 4 : Click to Zoom

ADDITIONAL READING :

Overemphasizing Power To Weight Ratio

* * *

That Strange Bicyclist, Alan Turing

noreply@blogger.com (Ron) — Wed, 02 Sep 2009 04:12:00 +0000

One of the reasons we have computers and can make it do wonderful things for us is largely because of one man. Alan Turing.

Turing is the founder of the ideas behind the modern computer and artificial intelligence. The idea of controlling the computer's operations by means of a program of coded instructions stored in memory is central to any modern computer and this brilliant idea first occurred in Turing's mind.

At a fundamental level, he was one of the greatest mathematicians that ever set foot on the planet and arguably the greatest computer scientist Britain ever produced. And one of his most celebrated specialties was in the much sought-after skill of code breaking.

True genius as he was, during WWII, he single handedly solved the unbreakable German Enigma code (the Wehrmacht model shown right) at Bletchley Park, through a code breaking machine he designed known as the Bombe. Much astonishing an act it is to build something that can crack a machine which produces on the order of 15000000000000000000 (15 billion billion) combinations of secret code.

In one of the pages of the book The Essential Turing by Prof. Jack Copeland (a truly breathtaking work), there is a profound statement that just struck me. It is estimated that the breaking of Enigma, and in particular the breaking of Home Waters Naval Enigma, in which Turing played the crucial role, may have shortened the Allied war in Europe by some two years.

Take a look at the WWII Casualties page here and turn two years into human deaths to get a rough perspective of its significance (you could assume that the German High Command is not destroyed in those two years while doing that).

But as history has it, geniuses such as Georg Cantor, Ludwig Boltzmann, Kurt Gödel, Alan Turing etc had a problem. Their stories show us that you be so ahead of your times with your ideas and can use so much of mind, body and energy to focus on answering important questions that it can take away something from you that others would call normal human behavior. Simply put, there is a possibility that having the mind of a genius can turn you into persons with strange personalities and impractical attitudes. Beyond a point, these aspects may cause events that can fight with your own sanity and drive you insane, ultimately to your own death.

Turing's life came to a sad end partly in this manner. And in his life, he had a fair share of eccentric behaviors that made him open to persecution. Take a look below.

Turing was athletic (he almost made it to the British Olympic Team in the marathon) and had something for the bicycle from an early age. It is said that he acquired a hero status at the tender age of 13 when he pedaled 60 miles alone from Southampton to Sherborne Private Boarding School after discovering there were no trains running that day. It wasn't the act of riding such long miles that needs mention but instead, the special sort of determination to do so that you hardly would expect from a kid at 13.

While working at Bletchley Park, Alan would use the bicycle to commute to work as well as to get around Cambridge. The bike, however, was an old and defective machine. It also had an interesting problem. As you pedaled it, every so often, the chain would pop off and disengage from the chain ring. Every time this happened, he had to hop off the bike and put the chain back on. When he finally made it to his office, he had to wipe his hands with a rag dipped in Turpentine from a bottle he had placed there.

He loved his dying bike and would not give it up for something better. In fact, he enjoyed riding such a poorly functioning machine that no one else could. So how did he ride it? Well, legend (from reading an article by Ian Stewart in Nature) has it that he chose the most tortuous path to devising a solution for the problem.

The logician in him theorized that if he could find a pedaling interval "n" after which the chain would fall, he could then time it in his mind and execute a special maneuver with his legs to prevent the chain from disengaging. That took a lot of energy so he devised a counter and fixed it to his bicycle wheel and analyzed the mathematical relationship between the number of spokes in the wheel, the number of links in the chain and the number of cogs in the crankset.

What he found was that the mishap occurred for a unique configuration of wheel, chain and pedal. On looking at the machine more closely, he discovered that this problem only happened when a particular damaged link on the chain came into contact with a particular bent spoke. So he simply straightened the bent spoke.

By golly, a bike mechanic or anyone with a reasonable amount of experience with a bicycle could devise an efficient solution in less than 10 minutes. It took him months. This lengthy approach to solving problems proves to us that he was a true mathematician and not a mechanic.

That's not all. Turing had a bad case of hayfever allergy from an early age. He rationalized that to filter pollen away from irritating and exacerbating the allergy, he would strap a gas mask on his face while riding his bicycle in town, even in the rain. He was indifferent to what others thought about this practice. He did it.

Other odd behaviors were made obvious. His colleagues noted that instead of acts like chaining his bike, he had a strange habit of chaining his coffee mug to a radiator in his office as theft protection. Turing, it seemed, had different priorities.

Was this Turing's bicycle and gas mask? This still was obtained from a Channel 4 News segment.

Despite these and many other odd behaviors, he was very a very honest, open and friendly man. Perhaps only too friendly and vulnerable, as he ended up revealing to the security services about his practice of homosexuality. In the cold war, homosexuality was seen as a defense risk, not just something illegal and immoral. Shocked with the revelation, they arrested him and had him sexually neutralized through organotherapy. This involved chemical castration by injection of female estrogen that later induced many physical changes and mood issues in him.

Unable to cope with the tensions that played out in his head during his years in medical treatment, Alan Turing retired to his room one evening at the age of 41 and killed himself, taking a bite out of an apple he had laced with potassium cyanide.

The incredible irony of his story is that of a man who wrote brilliant theories about the human mind and machine intelligence, being treated no more than a machine, to be controlled and put into discipline by humans, humans who in fact acted like machines who saw the world only in binary, in black or white paradigm.

More than 50 years since his death, thousands upon thousands of people have signed petitions asking Britain to offer a formal, posthumous apology for the ill-treatment of Turing. A man who should have died a war hero in fact died in utter shame, they say.

Whether he should be pardoned or not has been one of the ongoing debates of our times.

ADDITIONAL READING :

The Turing Archive : History Of Computing

Bletchley Park : Its No Secret, Just An Enigma (Telegraph)
Alan Turing : Code Breaker And AI Pioneer (1 Hour Video From MIT)
Alan Turing : Life And Legacy Of A Great Thinker
International Turing Apology Petition

* * *

The Fun & Modern Day Magic Of Bike Advertising

noreply@blogger.com (Ron) — Mon, 31 Aug 2009 04:00:00 +0000

That bicycle companies will go to odd lengths to market their products is clear when you pick up their catalogs and flip through their pages. If you manage not to drool all over yourself and drown in your own puddle, you may come across some odd nevertheless interesting finds.

The word cheesy in the urban dictionary means "shoddy quality". And I think when you devise cheesy marketing and drive it towards someone and his pocket while trying to attracting their interest, its sort of like shining a bright flash of immodest light in someone's face, ordering them to go blind and start believing through faith alone.

Perhaps immodesty is the norm these days? I don't know. But I wonder what space aliens might think of us when they arrive at our desolate planet many years later and excavate our sorry remains. All those piles of papyrus junk containing cheesy advertising might put them off. They'll probably just fly back in their space ships disgusted.

Today's case in point for illustration :

(Drumroll...)

Enter the Zipp Annual Product Catalog for 1993. I had this saved on my computer from sometime back and I doubt you can get this on the internet now.

Anyway, this piece of advertisement was a specimen alright. Open page 1 and you unmistakeably find yourself at the center of what they're trying to sell, an odd looking bike with bright red and yellow that does prove that red color has the marketing power of provoking emotional outbursts; repulsion could certainly be one of them?

And why, there's a quote on top of the prologue that asks the reader that he stop for a little more insight into this contraption. What might it be and will it inject him with some wisdom before his adventure?

It reads :

"Any sufficiently advanced technology is indistinguishable from magic" - Arthur C. Clarke

Of course, the great futurist and sci-fi author never said any such thing about a bicycle. It may have been hip in those days to quote Clarke anywhere and everywhere you found a spot begging for scientific blessing.

The quote is the third law in what is known as Clarke's Laws, provocative observations on the future of science and society that were published in his book “Profiles of the Future". The essays in the book covered a wide range of topics looking to as far as year 2100, exploring the conquering of gravity, conquering of time and space and so on and so forth. I wonder how an emasculated bike for half naked tri geeks connects with Clarke's imagery. It might have been the carbon fiber in the bike. It sounds space age.

Anyway, as we move on, we find more red and more yellow with blue and orange along with fancy graphs attached to unvalidated bursts of insight such as "our Zipp bike lets you save 19% of your energy at 30mph compared to competitor's frames." and how treating yourself to their "Ballistic Hubs" and "V-Rim" Technology" will never make you regret it, ever!

A question "what is there to think about?" adorns the end of that page, shooting the reader in the face for entertaining naughty contradicting thoughts and pulling him along for the rest of the thrill ride.

What is there to think about? Its basically just "Blazingly Fast"!

The next page is a full page motion blur image of a person riding on such a bike, almost like he's doing a 180 in a school zone. It seems to fly right past the reader and out of the page. That must surely captivate him. Wow, that is fast.

P.S : Photo editing sure works, but it must have been so bad those days that this rider in the blur came out to look more like Daffy Duck with a silly hat on than anything human.

Page 5 has another quote, another inkling of wisdom from great people :

"Those who create are rare; those who cannot are numerous." - Coco Chanel

Coco Chanel was talking about the fashion business and the creation of simple and elegant clothing for women. She quite possibly didn't give a French kiss about bicycles. But Zipp, perhaps to show how they both agree with each other's ideologies, throw in a picture of a track bike in a purple color so repulsive, perhaps the men at Zipp were taking their revenge out on the more fairer of sexes back home for nagging them so much.

Some near naked images of men show up in the following pages and then lo and behold, we are greeted with another quote, this time from none other than the late Prime Minister of India - Mrs Indira Gandhi. It is robust with grammatical error.

"My grandfather once told me that there was two kinds of people : those who do the work and those who take the credit. He told me to try to be in the first group; there was less competition there." - Indira Gandhi

Mrs. Gandhi was talking about the economic wisdom offered to her by her grandfather in a British India. If using Arthur Clarke to bless your bike was hip, quoting world leaders out of context with grammatical error while denigrating them between two near naked tri geeks was probably even hipper...or hippier.

But that's not all. After 11 truly entertaining pages of marketing, Zipp finally zips their campaign with one more imagery.

This is to suggest to us that they're winning the world over right from little Indiana.

A casual observer might see it as a harmless image. "What's wrong with that?"

Well, it would have been perfectly sane if it weren't for a final closer look at that odd flag at the 6 o'clock position. Let's magnify it some 200%.

What's this?!!

Why Ron, I've never seen anything like it before. Could it be the imaginary empire of Kuboojistan, told in tales by past house wives...that empire so mighty that their armies raped and looted other nations and had their flags miniaturized and sewn into theirs?

Or did the bleary eyed guy with the photo editor, late in the day, run out of space to place more flags of the world? Perhaps on finding that the coffee in the pot ran out, did he decide to call it a day and rush home after patching all the remaining flags together to form the mighty Kuboojistan?

I don't know. I maybe ignorant. But after this exciting exercise of swimming through a bicycle catalog risking being eaten alive, a reader could be forced to reflect upon the 3rd Arthur Clarke's Law :

Any sufficiently advanced technology is indistinguishable from magic, indeed.

Except, the magic is not so much in the bike.

* * *

Do you have recollections of cheesiness in bicycle product ads? Write to me here. Let's laugh together and be merry.

The "Dominant Left Theory" In Bicycling Crashes

noreply@blogger.com (Ron) — Fri, 28 Aug 2009 04:01:00 +0000

This blog brings you new perspectives and interesting ideas in cycling, without any charge. You may pay me back through your continued interest.

Some months back while visiting a good friend of mine, I happened to grab a vintage cycling book off his shelf and flip across its pages. I like the smell of old books. Its like battery acid for the mind of a book enthusiast, just stimulating. In one of its uneventful pages simply titled Appendix, I came across the following words. Read carefully, as the author comes across as completely assured of what he's about to theorize. I'll tell you who wrote this at the end of the quote.

"If you been riding long enough to have some falls, I'll bet that almost every injury has been on the left side of your body. How do I know this? Because its the same for me and many other riders. If you want to find an old bike racer, look for a guy with scars on his left elbow. There seems to be a physiological reason for this and it is very interesting, though it hasn't been formally documented as far as I know. It has to do with the location of the heart, the body's primary organ.

As we know, the heart is to the left of the center in the chest. When the body loses equilibrium, it has a strong tendency to fall toward the heart side. This also explains why most riders find it easier to corner to the left than to the right. And it's why track races go counterclockwise so that all turning is to the left. The reason it feels more natural is that the distance from the heart to the ground is less when turning left than when turning right. Even though track riders often do fall on their right side, this doesn't disprove the theory. It just points out the bike's tendency to slide down the banking.

Cozy Beehive edition of original illustration by Grid Designs

What is the practical value of all this? For one thing it means you may need more practice cornering to the right before it feels as natural as cornering to the left. It may also be wise to wear a protective pad on your left elbow in criteriums, especially if you've injured it before. Should you crash there is a better than even chance you'll land on it again. Keep this "left side" theory in mind and you may find other ways to use it for your benefit. "

The author of those words, documented in the 1985 classic Bicycle Road Racing, was none other than the Polish coach, Eddie B (also known as the father of modern American cycling). Being one of the most respected coaches in history, you'd think he'd make sense with his ideas.

This one is particularly interesting as he's stating that "almost every" injury is to the left side of the body because the body (if you consider it to be an inverted pendulum while on a bike) has a directional falling bias. It is also stated that because this "falling" is easier to the left than the right, cornering towards the left side is as well. Therefore, velodromes are run anticlockwise.

Today, you readers can be fellow mythbusters. I did my part, analyzing some 10-15 real world videos of bicycle crashes. I found no correlations with the statement above and all crashes highly depended on riding conditions. I also counted all my scars and there are more to the right side than the left. I don't believe gravity has a preference for this side or that side.....unless you can take a fresh cadaver, cut the flesh into two equal halves and find out that one side weighs more than the other. Are any of you active in criminal investigations? This whole thing begs me to ask : what side is a dead body more likely to fall towards? (If you have murdered someone, are in jail and use an iPhone to read my blog, let me know....)

So today's question : Is there biologically any reason behind the supposed tendencies to fall towards the left side, or is it just a subconscious reflex action to protect your derailleur and chainring from getting damaged? Ah. Think about that one for the weekend.

ADDITIONAL READING :

We Might As Well Crash

* * *

Dynamic Ride Comfort & Measuring Vibration In Bicycles

noreply@blogger.com (Ron) — Tue, 25 Aug 2009 04:01:00 +0000

The concept of ride comfort varies from person to person. If one were to ask 10 different people about a particular bike's ride characteristics, its likely they'll say 10 different things. There's probably a good reason for this. Physiologically, we can sense pain better than comfort because our bodies have lots of pain receptors (nociceptors) but there's little evidence of a comfort receptor. So our bodies are built without 'signal probes' for comfort. Therefore we tend to call something comfortable if there's no discomfort, i.e, if our nociception does not pick up discomfort signals. (If there's a more involved perception mechanism than what I've described, its outside the scope of this blog)

But even the perception of discomfort varies from person to person. A seasoned veteran testing out a bike is likely to have a different perception of discomfort on a given bike than a beginner may. Bicycle marketing literature as well as reviews of bikes usually are plentiful in these sort of subjective feelings that no one can put a number upon. X person tests the bike. He likes it. Finally, he places some arbitrary golden stars as rating against the bike in a magazine. What does the reader feel?

You'd want to snap - "Who cares about small numbers, just believe it and ride it!". Yeah, that's alright. But as bicycles get more expensive and new inventions border on that which is ridiculous, when bold claims ask for a lot of money in exchange, a customer would surely not mind knowing if there's true value in these claims or if there's some sort of daylight robbery going on.

Zertz - A marketed viscoelastic insert for reducing vibration. It comes standard on many of Specialized bicycles and cannot be removed or replaced.

One of those claims involve the relation of bicycle design with vibration reduction. For example, some years back, we saw Specialized incorporating an elastomer insert into their bikes at specific locations that supposedly "soaked up" the road chatter. Others have marketed frames and forks with special, curvy shapes that implied they're somehow better at vibration reduction, power transfer etc etc. Note that there is zero published technical evidence backing up the claims, yet people are quick to side with one brand or the other because of personal feelings.

This picture shows the harmonic tuned mass damper marketed by Bontrager as the Buzzkill Damper. This particular one was seen at times on Stuart O'Grady's bikes at the Paris-Roubaix. More on this can be found here.

One of the recent examples is Museeuw's biocomposite bike, a medley of organic flax and carbon fiber made in Belgium through a patented process that I've written about in the past. Their marketing strategy seems to be to make people believe that there's something really magical about its vibration dampening characteristics compared to competitor's bikes. Interestingly, they have joined hands with the materials engineering department at the University of Ghent in a partnership to do the R&D work. Apparently, one of the deliverables from the University would be an objective study of the bike's vibration dampening characteristics so that they can be presented to customers with commercial interests.

Recently, the 3D plot you see below was leaked out to the public on the internet after a Museeuw press launch. How it got leaked is a story you need not worry about. Anyway, the plot came directly out of one of the studies on the flax-carbon bike done by an individual named David Luyckx.

Fig 1 : This plot shows Damping Percentage vs Vibration Frequency vs Time for a Museeuw MF5, measured using two accelerometers mounted on the bicycle. Vibration frequency is a function of mass of the vibrating body, here, the bicycle and rider. Little is known to us about the test equipment and instrument characteristics of the accelerometers used.

He then compared it to the characteristics of 3 other bikes tested in the same study :

Fig 2 : This plot shows a comparison of vibration dampening of a (left to right) Pinarello Prince, Willier Cento Uno, Cervelo R3SL and the MF5

Now in the automobile and motorcycle industry, there are some specific ISO standards you have to follow to measure dynamic comfort and whole body vibration while sitting in a vehicle. None, as far as I know, exist that describe what to do incase of a bicycle. So David Luyckx set out to design his own experiment.

After reading his brief test report to us at rec.bicycles.tech, the following things can be said about the nature of his ideas and his experimental setup :

What To Measure : Ride comfort while using the flax-carbon bike, by studying trends in vibration dampening in the same (histeretic dampening). Specifically, the transmissibility of vibration would be measured. In other words, if there was a way to measure and determine the difference between the loads that were introduced into the frame and the loads that the rider would experience, it could be determined how "comfortable" a bicycle frame was quantitatively.

Experimental Setup : From his limited test report, Dave told us that he mounted an accelerometer near the rear wheel hub which he believed would give him an idea of the loads coming into the frame. A second accelerometer positioned just below the saddle on the seatpost would get him a measure of the loads before the rider experiences them. The difference, according to him, is how much of the vibration pie the frame takes eats away.

Methodology : All four frames - Museeuw MF5, Pinarello Prince, Wilier Cento Uno and Cervelo R3SL - were tested 4 times each with 2 clincher type rims (high and low profile) and 2 tubulars (high and low). If his idea was correct, by this method, he would not see too much difference between different wheelsets since he was only looking at only the frame properties between rearstay and saddle points. The measurements were done using independent accelerometers at a measuring rate of 50 Hz. The accelerometers were synchronized before the test. This enabled him to obtain a frequency spectrum of 0 to 25 Hz at any given time after putting the datasets through a Fast Fourier Transformation (FFT). He claimed this particular test method is comparable to how construction workers are monitored for whole-body-vibrations during their work. So, for every 27-second interval, the FFT-algorithm was used to get a 2D frequency spectrum, i.e. "frequency vs. load" graph. By using the 27- second interval he could avoid any response delay of the frame when impacted. By comparing each individual 27-second frequency spectrum of the rearstay and seatpost at the same interval, he was able to construct the 3D graphs shown above which involved approximately 300 graphs put next to each other.

Results : Final results showed a margin of difference of vibration dampening less than 5%.

Interpretation Of Graph : A value of "0.8%" on the y-axis in Figs 1 and 2, according to Dave, signifies that 80 percent of the original load is being absorbed or dampened somewhere between rearstay and seatpost. So he claims that the MF-5 dampens around 70 percent of the original load whereas the Pinarello Prince in Fig 2 absorbs only 45 percent of the original load measured at the rearstay of its frame.

Now I have to commend the fact that someone in the industry is taking the first steps towards thinking about how to measure vibration. But I must admit this is a very challenging task. It would take a lot more to convince people that the above basic testing makes sense. The graphs above look colorful but is confusing to interpret in 3D. The 5% of difference from the flax can even be argued to be practically imperceptible to any rider. As of now, the testing does not account for how the vibration can be affected by the following :

1. Amount of monitoring and placement of accelerometers - Can bicycle vibration really be fully captured by just two accelerometers on the bike? And how does their specific placement and mounting affect the frequency spectrum?

2. Cushy tires and a saddle - If you let some air loose from your tires, what's the effect on vibration dampening? Tires have significant roles to play in this aspect. It is well known that racers in the grueling Paris-Roubaix lower their tire pressures to about 80-85 psi to ride on cobbles. They even bend their elbows and loosen their grips on the handlebars to a significant extent. Also, if you have a cushy seat, the force on a rider might be tiny yet the accelerations on the seatpost may be large.

3. Varying frame geometries and designs - All 4 bikes tested have different geometries and aesthetic features. What effect do that have on vibration transmission or dampening? Can you say for certain that a curvy chainstay has zero measurable effect?

4. Frame flexing - A frame design is, to some degree, known to have comfortable ride characteristics if some level of compliancy is incorporated into the design. This means that the frame can flex finitely in a particular direction to reduce shock transmission and then transfer back the potential energy by acting sort of like a spring. If the flax frame reduces vibration by flexing, this can involve high forces. So one could theoretically make a noodly little frame which is poor in power transmission but perhaps great at shock absorption. So the above study does not establish conclusively whether the claimed vibration dampening in the flax-carbon frame is infact from the vibration soaking capabilities of the flax-carbon material or because of the flexing of the frame due to the mechanical properties of the overall structure.

Infact, I did a little research on the stiffness characteristics of the MF5 flax bike to try and make sense of point number 4 above. The German Tour Magazine, an independent 3rd party testing agency for top end bicycles, tested a 56cm Museeuw MF5 a while back. This is the same bike shown in Figs 1 and 2. After some translation, here's what I believe I found :

Let's put this above table into perspective.

Early this year, the same independent magazine tested 27 top end carbon fiber bikes that you can buy for money. From the published test results, I calculated that the average torsional stiffness for those 27 bikes was on the order of 95.85 Nm/degree, the average bottom bracket stiffness was 55.77 N/mm and the average lateral stiffness of the forks of these bikes was 43.81 N/mm. So compared to those averages, the flax MF5 bike appears to be 29% lower in torsional stiffness, 21% lower in bottom bracket stiffness and 10% lower in fork lateral stiffness. This isn't sensational in the market, especially for the price of the frameset alone, a whopping 5000 dollars.

However, that's not the point. Suppose its these low numbers of stiffness that's providing all the "vibration soaking effects" in the flax frame? This can be a valid correlation, why not? Afterall, we all know that an overly stiff bike is not comfortable for long rides.

I'm eager to know more from David's side of these investigations and how this develops for the future. However, it stands right now that what he's taken upon himself is a challenging scientific task. If the outcome of these studies are minute percentage differences of one bike over the others, then someone can easily lose sight and perspective of the scale of numbers. That must be kept in mind. Meanwhile, I would encourage him and others who're on the same boat to look at the automobile industry, especially that of motorcycles and also study ISO standards on how to go about setting up experiments and measuring whole body vibration while using a vehicle.

If any of you are particularly interested in this topic, or is experienced in measuring vibration in your fields of work, please do write in to me with your thoughts here.

ADDITIONAL READING :

The Biocomposite Bicycle Part I
The Biocomposite Bicycle Part II
Whole Body Vibration According To The ISO2631 Standard
Bicycle Structural Dynamics Research

* * *