6 Dynamic Stability Of Bicycle Design : Part 3

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 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

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8 Dynamic Stability Of Bicycle Design : Part 2

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

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4 Dynamic Stability Of Bicycle Design : Part 1

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.

OR

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!

Learn How to use the principles of stability. For more Aviation How-To Videos & Articles, visit WonderHowTo.

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

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14 Discuss : Contemporary Body Culture In Cycling

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

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15 That Strange Bicyclist, Alan Turing

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

* * *

13 The Fun & Modern Day Magic Of Bike Advertising

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.

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

43 The "Dominant Left Theory" In Bicycling Crashes

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

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17 Dynamic Ride Comfort & Measuring Vibration In Bicycles

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

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10 Safety Moment : Colliding With A Taxi At An Intersection

Jody Leonard after a car-bicycle collision

Good afternoon. Recently, a reader of my blog sent me this moving account of how he came to see the realities of a bicycle collision with an automobile.

Less than a month back, Jody Leonard who works for Deloitte & Touche LLP in Washington DC got into an accident with a taxi at an intersection. I really hope he recovers soon.

Here's a little of what he wrote to me :

"I was finishing up a training ride on a fine evening last July when I was hit by a taxi cab. I was traveling north bound on 15 ST NW toward Constitution Ave and the taxi was going south bound on 15th. This road runs in front of the Washington Monument. At the intersection of 15th and Madison, the driver made a left hand turn onto Madision, the wrong way down a one way street! I was struck by the car as I crossed the intersection at speed with the light. I don't believe he saw me at all.

So long story made short : 9 hours in the Emergency Room, cracked ribs, fractured nose, lacerations, abrasions, etc. but no head trauma as I was wearing a helmet. The driver, meanwhile, was issued a ticket by the US Park Police for an illegal left hand turn.

The Doctor estimates about 4 weeks for everything to start feeling normal again. The cab driver remained on the scene, but it was the many bystanders who came to my aid. This happened in front of the Washington Monument at the tail end of the DC rush hour and park police and EMTs were on the scene in less than 5 minutes. I was very lucky in that respect.

As for liability, in my mind the driver was clearly at fault, but accidents involving taxi cabs in the District are historically hard to deal with. So I took the advice of Bob Mionskie - former Velo News legal columnist - and hired an attorney. By the way, taxi's in DC are only required to carry the minimum amounts of insurance coverage, I really don't understand this since commercial trucks must carry at least a million dollars of insurance, and they don't ferry people around!

The worst part of all of this is my bike is toast! The pictures are deceiving since the entire frame is torqued. Both tires were blown out from the impact and my local shop tells me that the rims (Mavic Ksyrium Elites) are not bent, yet they tell me the wheels are so far out of true and tension that they cannot be salvaged. I'm wondering how this happened? So it looks like I'm out a frame and wheels, a drag since I love that wheel set!

The road back to 100% fitness has been very difficult, but I think I'm getting there. I believe it is important that people take away two messages from what happened to me. They are :

1. No matter how defensively you ride, there is always the possibility of another person's inattention and carelessness, both of which have the potential to cause great harm.

2. Always wear a helmet. I know the last causes consternation among a few who are vehemently against it, but I am certain that I would have had serious brain trauma. If it wasn't for the helmet, the crack would have been on my skull instead of the foam."

Helmet Front

Helmet Left Side Exterior

Helmet Left Side Interior

Interior Crack In Fresh Light

A torqued 7005 series Aluminum bike, much useless now

Other safety moments can be accessed here. If you have an interesting experience of your own to share, please write to me.




ADDITIONAL READING :

Deceleration And Force Of A Helmeted Head Impact

John S. Allen : Riding Through Intersections (Chapter 3 From The Online Book 'Bicycling Street Smarts')

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