Hmmmmm? photo: @fat cyclist
This is perhaps painfully obvious to everyone but me and if so, sorry I’ve yet again wasted your time. The other day, after falling off another floating board in the ocean I had to admit my balance might suck. And my coordination too or I might have been good enough at baseball to actually like it and play it. Nope, ball sports are right out. What I want to celebrate is the fact that our bikes have two magic gyroscopes spinning underneath us. You want to sit up at 40 kph, casually reach behind and tuck your gilet under your jersey? Be my guest but you can only do that because of the gyroscopes, not your awesome balance. If good balance was required to ride bicycles every prat and his brother wouldn’t be chatting on their iphone while zipping down the lane.
Descending at great speed is so damn much fun because the bike is rock solid when hauling such mighty ass, until it isn’t and that is is pilot error, not the fault of your dualing gyroscopes. To quote one of Maine’s greatest exports, Yvon Chouinard, “speed is safety”. He was talking about mountaineering and the need quickly get across exposed couloirs to avoid potential rockfall or avalanche but it’s also true for cycling, to a point. OK, he could have said speed is stability if he was more of a cyclist.
Does this mean we shouldn’t own deep section carbone wheels, with their lighter rotating mass providing less momentum? No, folly my friends, the deep section wheels are spinning faster because you are going faster due to the aero-awesomeness of those wheels. A year into my tubular tire/50 mm Cancellara carbone wheels and I’m more chuffed than ever about them. Unless it’s raining heavily and I’m descending then, not as chuffed. But I digress, that is another lecture.
So far so good. What the hell is absent minded professor talking about? All this spin angle momentum and torque should have us riding in circles not going in straight lines. That is your weekend homework. Test on Monday. Buon weekend.
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@Gianni
Agreed; amazing stuff. And for some reason, while being absolutely awe-inspiring, the cycling robot strikes me as hilarious, too - in a very good way. That little wave at the end of every successful ride is priceless.
The professor is Dutch, so he must be right.
No fair. It's already Monday morning and I'm just finding out about this test. Will a note from my mother get me out of it?
@Ron
I suspect it comes down to the length of the axle at the point of suspension. Net abstract conclusion is that the fact that we mount the axle at both ends cancels it out as it goes the other way when you reverse it. Alternatively it proves that the forks should attach at the centre of the hub - which would be interesting in a number of ways (mostly resulting to risk to life and limb). Then again Cannondale have the Lefty which should go round in circles.
interesting topic: but how does this physics explain speed wobbles?
I've experienced and seen some shockers - even in the recent Amgen Tour of California one of the riders in the break had a pretty obvious case. I've read and listened to a variety of explanations but none seems to consistently explain the phenomenon using science.
Anyone?
@PT
I suspect longitudinal flex and spring starts to come into it. Many moons ago I used to ride good old solid British motorbikes. Built like the proverbial brick shithouse. A mate was into new fangled Japanese stuff. So one day we swapped bikes. Basically after getting used to something that felt near half the weight of mine I decided to see what it could do. Went into a bend fairly quickly (but not excessive) notched a gear down on the exit and opened it up. SHIIIIIIIITTTTTTT ! I felt the frame flex then was hit by a ginormous speed wobble. Scared the proverbial out of me. Went back to my mate and asked him if he'd ever had issues in fast bends - he never had. So I concluded he had never really pushed the thing.
@PT
@PT
I was riding down a hill in the rain, a little under-dressed, and got a persistent speed wobble. I thought it was a problem with the bike, but after a while I figured out that it was caused by my own shivering. Sorry, not a useful answer.
@Teocalli
I tried a backwards bike that was brought in to the LBS by a prof from our local university. You very quickly realize there is no chance. I wasted maybe 20 sec's giving it a try. This cat stuck to it for 8 mo's! Then couldn't ride a regular bike !!!??? Yowza.
@geoffrey
Speed wobbles can be caused by frame construction/alignment/forks/centre-of-gravity/rider weight/rider build/muscle tension/lack of tension/ability/headset problems/wheel construction/tyres/loose quick releases/wind/road surface or any combination of those factors, and probably others I've forgotten.
That's why speed wobbles are still on the whole a bit of a mystery; almost every case is individual.
I fucking love physics.