Why doesn’t my bike fall over? It is a beautiful example of physics in action.
Have you ever wondered how it is possible to give a bicycle a good push and it will keep running 10, 20 feet or even longer without falling over? Now the world of science has an answer.
One of my favorite pastimes is listening to podcasts. I listen to a wide variety of content, with an emphasis on research and technology. Today I listened to the BBC Science in Action podcast from April 14 which among several things addressed the topic why bicycles (and by inference, motorcycles) are self balancing.
Most people will say it is due to the gyroscopic effects of the wheels turning and the effect of trail (or caster) of the front wheel. The new result is that you don’t need either of these effects for a bike to be self balancing. The answer is amazingly simple.
Andy Ruina from Cornell University has proved this by building a bicycle where both these effects are cancelled out, and shown that the bike can still be self balancing.
Here is the explanation: Typically, the center-of-mass at the rear of the bike is higher than the center-of-mass at the front. As the bike falls, e.g. to the right, the rear wants to fall slower than the front of the bike, with the result that the faster falling front-wheel turns right, i.e. it turns into the turn, and thereby pushing the bike back upright – it becomes self balancing.
Isn’t that beautiful?
There is more of Andy’s bike research available at his research site: http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/overview.php. Specifically, check out the video that shows the self balancing properties in action.
Now I have to think about what this means for riding a motorcycle at speed, when quite different mechanics come to play. What do you think?