If we ask the reverse question: "what makes a skyscraper fall? The answer is:' an earthquake, or any other event that can make gravity prevail". I hate to make long posts, but I had to refute one by one all the fallacies that have been proposed.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why do we fall down when the bicycle slows down? Asked 7 years, 2 months ago. Active 2 years, 9 months ago. Viewed 32k times. Improve this question.
Lakshmanan Kanthi Lakshmanan Kanthi 2 2 gold badges 3 3 silver badges 10 10 bronze badges. Think of it as a cross-post. That's a bad precedent to set.
I'm not going to rant on Meta about it or anything, it's just my polite way of saying I disagree. And since the question already had four reopen votes it is hereby reopened!
Show 5 more comments. Active Oldest Votes. There is a force due to friction that deflects the rider's path into a curve: The frictional force pushes against the base of the bike and acts to stand the bike back up vertically.
This answer becomes obvious when you ask yourself questions like: What happens if you are riding quickly when you cross a long patch of ice? Improve this answer. Brandon Enright Brandon Enright I think you can see a similar effect with a rolling coin - when it tilts over to one side, it will roll in a curve and stabilize again if it is fast enough, if the coin rolls slowly it will just fall over You're always falling one way or the other, and you're compensating by always moving your point of support to counter your fall.
Gyroscopic precession helps you do that, but isn't necessary. There are ski bikes that don't have wheels. Add a comment. Community Bot 1. It answers the question even though you don't directly say that you don't like purple. It is the additional input of dismounting that causes the bike to fall, not the absence of the rider itself. This can be shown in some motorcycle accidents where the bike keeps going without the rider. The angular momentum is far greater than on a push bike eclipsing the fall in the same way a gyro self-corrects.
Heavier tires and far higher RPM in the wheels and transmission. Eliminate road surface defects, non-apparent airflow and the steering and you will see balance.
See this video , especially the second half, where it recovers the balance by itself after perturbation. Eldritch Cheese Eldritch Cheese 1 1 bronze badge. In particular, a rigid body at equilibrium on a surface is stable against small perturbations if and only if: its center of gravity is above the interior of the support region, so that slightly moving the center of gravity will not move the object out of equilibrium; or more generally, the shape of the contact surface is such that slightly tilting the object will move the contact area in the same direction as the center of gravity, but further.
A slow-moving, or stationary, bicycle will not be able to do this, and therefore is not stable. Ilmari Karonen Ilmari Karonen To add some information on the "why we fall" question: The bike is unstable in any case in the absence of a driver. Even if it is not the main factor, the feedback controller riding on the bike the human is surely important, for the simple observation that we are well able to walk, i. Such a controller is clearly capable of significantly contributing to the bike's stability.
It is exactly the same principle that makes a spinning top fall when it spins slowly. There are many factors that make a bike stable, and momentum is only one of them, but the determining factor that makes it fall is that angular momentum is not strong enough to produce the necessary self adjustments, and gravity prevails on its resistance to have its axis of rotation changed: here that factor is magnified and the bike is more stable In this video Bernhard's? The answer is:' an earthquake, or any other event that can make gravity prevail" I hate to make long posts, but I had to refute one by one all the fallacies that have been proposed.
I'm pretty sure I once saw a video with a counter-rotating wheel, such that the net angular momentum is zero. And in it I believe they also stated that one of the reasons for stability is the angle of axis with vertical of the steering wheel and the distance between the axis of the front wheel and this axis of rotation of the steeringwheel.
I have read papers which claim that the lateral torque delivered by an adjustment to the steering axis is proportional to the velocity, and that this torque is what causes the bicycle to stay upright more so than any gyroscopic effects. There is a contribution but the majority of the stability comes from the rider. This is why a rider can track stand stand still without falling over. The other is that a bike behaves like a castor on a shopping trolley.
People assume the actual ground contact point of the front wheel is in front of the steering axis because of the head angle and fork rake. But actually the wheel contacts the floor just behind this axis. So like a shopping trolley, push your bike forward and the front wheel necessarily tucks in and trails behind the direction of travel.
And the contact point of the front wheel lies ahead of the steering axis, not behind as with a castor. To explain this, the researchers posit that the distribution of mass, particularly on the steering assembly, is key. When the front of a bike falls, it falls faster, just as if you balance a pencil on your hand it will fall faster than a broom.
Thus in an attempt to fall faster the front end causes steering and brings the bike back under itself. One of them is the gyroscope effect and the other is the caster effect. What we've shown is that those two effects aren't actually necessary.
The front wheel of the bicycle is spinning forward quickly, acting like a gyroscope. Then when you tip the bike to the right, the gyroscope applies the torque, which turns the handlebars to the right and causes the steering, bringing the wheels back under the bicycle and holding it up.
The [caster effect] is a self-aligning effect to keep the steering straight. Look at the bottom of your office chair. If you move your chair around, the wheels reorient themselves to follow the motion.
This is because the wheel's ground contact point is behind the chair's steering axis; the wheel trails behind. The front wheel of the bicycle also touches the ground a little [behind] where the steering axis hits the ground.
If the bicycle direction changes when it's going forward, the wheel will tend to follow and bring itself back under the rider. If you just solve these big, messy differential equations without thinking about them, they say a bicycle should be stable, but they don't tell you why.
He started with a model that had 25 parameters and got it down to eight parameters, and that bicycle could still be stable. So about three years ago we convinced [study co-author] Arend Schwab and his students in the Netherlands to build a bike like that and see if it really worked. And it did. Jim proved it mathematically and then we put it in practice. If we push our self-stable bicycle straight, it goes straight, but it's really self-correcting and weaving back and forth like a regular bike.
If it falls to the right, it steers to the right.
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