By Lennard Zinn
Before moving on to less important matters, I’d like to acknowledge the passing on Monday of Sheldon Brown, one of the giants of bicycle maintenance, technology and general bicycle mechanical understanding.
He will be sorely missed, particularly for those seeking simple, straightforward answers to a vast array of bicycle-related questions. His white bearded visage with eagle-adorned helmet has long been the online face of Harris Cyclery in West Newton, Massachusetts.
A frequent presence on rec.bicycles.tech, Sheldon often shared his enthusiasm for all things three speed and reminded us all of the beauty and simplicity of a bicycle without the latest number of speeds and carbon doodads. The acronym “AASHTA” (As Always, Sheldon Has The Answer) must sadly finally be retired.
Sheldon died at age 63 of a heart attack, but he had struggled with his health of late. Seven months ago, he was diagnosed with primary progressive multiple sclerosis, which took away his ability to ride a bike, after which he had switched to riding a recumbent trike. May you roll forever on two wheels, Sheldon.
Last week, I discussed the first day of the second annual SICI Cycling Science Symposium and Expo and would like to add a bit to that.
One of the things I touched on last week was the Active Spoke from Tarryan Technologies, which is a spring-loaded weight sliding on a wheel’s spoke. I find the idea to be quite fascinating.
As the wheel’s rotational velocity increases, the weights are thrown to the outside of the wheel, effectively concentrating more mass out at the rim. And as the wheel slows down, the springs retract the weights back toward the center, effectively decreasing the rim mass. Inventor Russell Kalil originally came up with the idea while riding an interval workout on a stationary bicycle with a heavy flywheel.
“I thought it would be great to harness the momentum produced by a wheel with heavy rim weight, but with the advantages of a lightweight rim wheel during a hill climb,” says Kalil. “It’s like a figure skater doing a spin with their arms out; when they pull their arms back in, their spinning rate increases.”
He first utilized long, hollow fishing weights connected to rubber bands on his spokes. Now, the system is quite elegant, incorporating thread-together modular weights with a slot in them so that adjacent segments causes the slots to be offset and lock the weights onto the spoke.
I got a set to try, and the amazing thing is how strong the springs are. Two spring rates are available; there are springs for normal folk and then there are “professional” springs, which are much stiffer. The wheel must be spinning much faster for the same mass to move out to the rim with the stiffer spring, and you can tune the system to your preference not only with stiffer or less stiff springs, but also with different stacks of masses, as they thread together.
The angular momentum of each mass about the hub increases 16 fold as the radius to the mass increases from 3 inches to 12 inches. The idea is similar to what Ondrej Sosenka was thinking when he set the world hour record on a 10-pound rear wheel – the wheel’s high angular momentum maintains speed better, except that Active Spokes are not as hard to accelerate once you slow down, since the masses are concentrated near the hub. Active Spokes aid you in going downhill faster and carrying your momentum up the next hill.
Pro rider Dirk Friel has tested them a lot and has set his personal best in the Wednesday Boulder time trial series with them. He correlates his frequent 5-mile test runs north of town with data on wind speed, direction, and barometric pressure from a nearby weather station and says that, once he has corrected for the wind, he is consistently faster on a rolling course with Active Spokes.
The importance of fit
On day two of the symposium, I went to two fit clinics, one by Todd Carver of Retül, and one by Paul Swift of Bike Fit Systems. Carver’s company makes a video motion-capture system to digitize a cyclist’s leg movements and thus analyze his or her position. Swift is the inventor of the Big Meat cleat wedge, which, in a post-Google search environment, has opted for the more palatable name of “Cleat Wedge.”
Using LEDs stuck onto the little toe joint, the heel, the ankle, the knee, the hip, the shoulder, the elbow, and the wrist, the Retül camera, actually composed of three cameras in a long tube, captures a 3D video view of the rider’s pedaling motion. The computer screen displays the knee, hip ankle, armpit and elbow angles at both the top and bottom of the stroke. Once the rider has been reduced to stick figure on the screen, it is much easier to pick out inefficiencies in the pedal stroke.
Carver made two important points that stuck with me:
1. – Don’t look at the knee angle until you have addressed the ankle angle first, since the ankle is the joint where the body adapts to a poor position.
2. – Dynamic bike fitting requires a fan (and the corollary to this rule, namely that if a fitter does not have a fan, he or she is not doing dynamic fits).
Swift’s fast-moving clinic addressed only three items: stance width, foot rotation, and foot inversion/eversion (the inward or outward tilt of the foot). Noting that the most common cycling injury is repetitive stress due to misalignment, Swift made clear the depth of his passion for fitting riders by saying, “I can’t sleep at night leaving somebody misaligned.”
Assuming that the rider is already set up well as far as saddle height, fore-aft and bar position go and that the fitter knows how to do this, he quickly went through how to put markers on the toes and knees and look at the rider pedaling with a vertical laser line connecting the knee and toe marks. He showed how to move the rider’s foot under the knee if they are not lined up by moving the cleat laterally on the shoe. And if the knee rolls inward or outward, he showed how to stack up his cleat wedges under the cleat to tip the shoe outboard or inboard.
He directed potential fitters to constantly ask the question of the subject “Where is there pressure?” He explained that the answer will be a clue and that the fitter can discover the source of the problem by using their answer and asking themselves the related question, ”Where is there not pressure?”
During a question and answer period, Swift and Andy Pruitt tackled a question about the compression of the iliac artery in the crotch that can occur from pedaling knock kneed. The symptoms are a “dead” leg. The discussion included speculation regarding Ryan Trebon’s recent problems.
The final day of the symposium saw the presentation of many abstracts for research currently in study or soon to go into study. As always, the symposium posed as many questions as it answered – a perfect place to head out for another year of research before reconvening at next year’s SICI Cycling Science Symposium and Expo.