Anyone who has learned to ride a bicycle has experienced the feeling that one will never master it until suddenly, you get the hang of it and feel that sense of exhilaration as for the first time you cruise along without fear of falling. The bike now seems so stable that you cannot imagine why it took you so long to learn. But why it is so stable is not easy to understand. I have written before about how the stability of the humble bicycle is actually quite mysterious from a physics point of view.
But once you have learned to ride it, it seems like you can never forget it.
But is that true?
From reader Tadas I got this fascinating video about someone whose friends gave him a bike that they had adjusted so that when you turn the handlebars to the left, the wheels turn to the right and vice versa, and invited him to ride it. The video shows what happened and what he learned from the experience of trying to master what he thought should have been easy.
It is not very helpful in learning to ride a bicycle to be given the instruction: Turn the handle bars so that the curvature of your trajectory is proportional to the angle of your unbalance divided by the square of your speed. As Michael Polyani put it, the skill is tacit. — Philip N. Johnson-Laird
I just saved a bike from being sent to the dump. I know what its future is now. Thanks for posting.
I put this problem in the same class as tides, economics, and biology -- too complicated to be interesting 🙂
But I did love riding.
I seem to recall as a child visiting an “amusement” (presumably more for spectators than riders) park having bicycles that had:
A: Steering wheels instead of handlebars
B: Reversed forks like this one
C: Off centered wheels
… utterly impossible to ride of course, that might just be a product of too much alcohol in the intervening years, however.
It’s also worth noting that most bicycles are largely self correcting (the effect is a lot more noticeable on motorcycles which are much heavier), the rake and trail of the fork causes the front wheel to turn into the lean increasing pressure on the inside grip pushing against the direction the rider is trying to turn the bars -- this pressure comes naturally as the bike leans over because you put more pressure on the inside bar as it falls into the turn to try to keep yourself upright.
As a bike starts to fall over, it’s specifically set up to slow the rate of the fall, the biggest thing you have to do when you’re learning to ride a bike is simply learn to not fight it.
This bike however requires you to now put pressure on the outside bar, effectively pushing yourself into the turn, which goes against everything you’ve told yourself and also requires a constant stream of conscious inputs rather than letting gravity do the trick.
I guess what I’m saying is that this bike is a lot harder to learn to ride than a regular bike because it’s not just steering in reverse, but it’s inherently more unstable because as it starts to fall over, it has the effect of accelerating that fall rather than slowing it.
Mano,
I recall a disastrous (but educational) afternoon at about age 12 when my friends and I challenged each other to ride our bikes with our arms crossed. We were at least smart enough to attempt the challenge in my backyard, away from concrete. After about 30 minutes or so of many tumbles, two of us managed the feat and rode in this manner for about 20 feet.
The interesting bit, the part we didn’t anticipate, was that we had to then relearn how to ride the bikes in the normal manner. The reversion only took about five minutes, but we still crashed several times before we regained the original skill.
Jeff
Mano,
Also, there is possibility that a similar situation was responsible for the sinking of the Titanic.
Jeff
Have a look at this guaranteed trip to the emergency room:
http://www.unicycle.com/club-2-wheeler.html
This is particularly evil, because on a unicycle your forward/backwards balance is managed by pedaling harder in the forward direction to correct for falling forward, and resisting against your forward pedaling to correct for falling backwards.
I’ve seen this device generate some remarkable strings of expletives at conventions for jugglers.
An interesting story on bike stability: a friend of mine had a frame builder make a touring bike frame with integrated racks to take himself and all his gear remote outback camping. The trouble was, no matter how he rearranged his load, the bike developed a barely controllable shimmy at around 25 km/h. After a couple of return trips to the frame builder to have the geometry altered he had to finally give up. This was after it tipped him off and broke his wrist when a long way from the nearest town. Luckily two of his buddies rode back and fetched him out by car. Anyway he cut up the frame and reused the components on another frame. Imagine his horror when the new bike did it too. He finally worked out that the front suspension forks were the cause of the instability. Something to do with their damping or sloppiness. With different forks he can now ride as fast as he needs to.
He may be full of crap* when he talks about a child having more neural plasticity than an adult, though. He had talked about falling back into the “old algorithm” and “unlearning” the old way to ride, which is more of the key here. He’s had more time for his brain to get molded to that way of thinking than a child. So it’s not that his brain is necessarily less plastic; it may be that his brain has to undergo more changes than a kid. And since it has to undergo more changes, it thus takes more time to reach the goal state.
* At the very least, his reasoning is flawed and does not support his conclusion.