Does anybody know why a bicycle will stay up just fine when your moving but when you are stopped its almost impossible?
Physics and a Bicycle
- Thread starter Michael Pisarri
- Start date
While gyroscopic precession is a property of gyroscopes, the property that allows the bike to remain upright while riding is called "gyroscopic rigidity" (or something like that). That is the tendency of the spinning body (bike wheel) to to remain rigid in space (upright). Precession is another neat property of all spinning bodies, but isn't what keeps the bike upright.Jaguar27 said:Yes, it's called "gyroscopic precession" if you google those two words there should be a ton of info on it...(saves me some typing)...in fact, a Bicycle is one of the best examples of this...not to mention the most fun
a fun way to mess around with this is to sit in an office chair that can spin and take the front wheel off your bike. sit in the chair and spin the wheel as fast as you can and then hold it like your the fork. then tilt it slightly and you can get your chair to move and it makes your arms feel funny. haha
Actually, gyroscopic forces aren't present in significant quanities until you get over about 15 mph on a bicycle. Countersteer is what keeps a bike upright at slower speeds. Riding no-hands is harder below about 15 mph because below that, the gyro forces haven't built up enough to keep the front wheel pointing basically straight, even though steering is fine below that speed. Ice skaters can balance on one skate because they steer to balance; no gyroscopic forces are needed to keep them upright. Bicycles behave similarly at low speeds. Ever tried to ride at below 2 mph? You'll really feel it down there.
You know, that is interesting, about riding at or below 2 mph. It can be done, but your body is adjusting a lot in order to keep you upright. It isn't just physics in play, but the processing/reaction speed of the brain that amazes me. Try to create the same simple task with a computer controlled 'robot' [or whatever], and you'll spend millions of dollars and endure countless failures to reproduce it.
not impossible, really. when i started toe clips 'n straps were the rule. a guy i rode with introduced me to track stands. i asked, "how long can you do that for?"
answer: "long as i want" and this guy was not boasting.
i still do the trackstand even with clipless, not often though as i seldom stop.
answer: "long as i want" and this guy was not boasting.
i still do the trackstand even with clipless, not often though as i seldom stop.
Michael Pisarri said:
A great example of "gyroscopic procession", also called "phase lag" sometimes, is the control input from the cyclic to the rotor blades in a helicopter. It's a pretty weird phenomenon. Any input made in the gyroscope (in this case the rotor disc) doesn't manifest itself until 90 degrees later. And I would argue that this is equally as fun as cycling!Jaguar27 said:Yes, it's called "gyroscopic precession" if you google those two words there should be a ton of info on it...(saves me some typing)...in fact, a Bicycle is one of the best examples of this...not to mention the most fun
Of course the control rods of any modern helicopter compensate for this so the pilot moves the cyclic in the direction he really wants the disc to move, but poor Igor Sikorsky flew his first prototypes with no such compensation...if he wanted to tilt the disc fore, he had to move the cyclic right, etc. Yikes!
I think it's a combination of gyroscopic precession and the body's own ability to retain balance. The latter probably applies when cycling at very low-speeds. A lot of tricks pulled off on BMX bikes pretty much defy gyroscopic precession and can be attributed to the forces exerted by the rider.
It is mainly due to the gyroscopic precession that I know of. I remember many of my friends talking about this as well and one of the reasons is that you have much less time to react to the balance if you are slower than you going faster.
