The balance idea is raised and rejected, but as I understand it it's a huge part. The issue isn't about humans balancing on the thing (as with the examples of canoes or horses that are already stable at rest), but rather that a bicycle _does not balance unless it is moving_, and moreover making it balance depends on the fact that it has steering – fix the front wheel in place and you can't ride it.
This is not intuitive, except with the benefit of hindsight.
I think the author should give more credence to it not being intuitive that people could easily learn to balance on a bicycle. The other examples he gave - horse, canoe - are stable without a rider. If you put a canoe in the water, it will stay upright. Horses, obviously, are stable without a rider. A bicycle without a rider will fall over.
I don't think it's obvious that putting a human on a long, two-wheeled vehicle will make it more stable than that vehicle is on its own. I think it's also not obvious that most humans can quite easily and quickly learn how to balance a bicycle.
It does seem utterly counterintuitive that a vehicle that cannot balance by itself would be able to balance with the addition of a heavy rider elevating its center of gravity. Usually making an object top-heavy renders it even more unstable, and bicycles are not stable to begin with.
And adding a rider on top of a bicycle does make it more unstable, but the amazing flexibility of the human brain allows us to transform that instability into stability, kind of like how modern fighter jets are intentionally unstable to make them more manoeuvrable.
Bicycles are a marvel of physics and biology working together.
The problem is the belief that is hardwired into the humans basic instincts about balance. We see the bike and we see balance problems and danger (not that this doesn't have that) but they probably thought of that and are working on it.
It doesn't matter how the bicycle balances, just that inventors thought it to be possible. Gyroscopes could have inspired that belief. Balancing was probably discovered in a "it works if we design it like this" manner, rather than from first principles.
That's not a fair continuation of the thought, is it? Even balancing on an entire rotating log isn't trivial. The problem here is standing on a small patch of surface that is moving under you.
The required insight for the bicycle is that, counterintuitively, a rolling wheel doesn't fall to either side. The axles, fork, frame, and seat are 'just' the elaborate way of mounting yourself to those rotating discs so that you can move along with them while sitting still.
Yeah. My point is that balance isn't an issue on a bike. The rider might not be able to hold on, but a bike is perfectly capable of keeping itself upright. Sometimes even to the detriment of the rider.
Low speed accidents where a rider drops a bike isn't enough of a concern to design something like this, so I'm ignoring those for the above statement.
That sounds like a unicycle, which is a hundred times harder to balance than a bicycle.
The physics of how a bicycle balances itself when you are moving is very different than that, complicated, and quite unintuitive. Basically when the bike starts to lean to one side, the rotation of the front wheel causes it to steer to move the bike underneath the direction you are leaning. This happens several times a second, and faster than a human can react.
The opening of the video describes the difficulty (impossibility?) of balancing a bike with the handlebars locked.
I've had frustrating arguments with engineers on the degree to which the gyroscopic effect of the bicycle wheels are what keep the bike upright. They seemed to think it's the spinning wheels that allow you to balance. (I suppose in their minds this would explain why it is difficult to balance when rolling very slowly.)
Give the bike a brisk shove, I argue, with no one on it and see how far it balances. In my experience, a bicycle balances for about as long as it takes to fall over.
I see the rider+bike as an inverted pendulum ... or like someone balancing an inverted broom on the tip of their finger if you will. Steering is the rather counter-intuitive means by which one moves the contact point with the ground left and right under the larger mass (the rider) to balance it.
Maybe the opening to the video or the Arduino-controlled contraption (lacking gyroscopic wheels) will get more people to re-think this.
OK - this is probably my ignorance talking, but why is it surprising that bike are balanced? The pedals are basically shoulder width and staggered, which is a very natural position for people to balance in as bipedal creatures? in addition, while the bike is moving, won't the inertia tend to keep things moving in the same direction?
This is all coupled by the fact that the rider is actively piloting and adjusting the bike to keep it under control at all times. The bike seems like it would balance to me because the control mechanisms are designed to keep things balanced easily.
> Since the wheel doesn't roll side to side, I imagine it's much the same as balancing a bicycle.
A bicycle moves. A stationary bicycle is impossible to balance (for most people anyway). I don't see how this would be any different. As soon as you stop you fall off?
If it were me I'd add two small wheels (training wheels? :) on springs + shocks on either side. (Make them fold in to maintain portability.) You'd have to make the spring force tunable for different people, but that should be possible by adjusting a screw to change the effective length of the spring.
At least bicycles are stable. This onewheel thing cannot work without a computer balancing it (+ the rider). If it fails the rider falls on their face. It would be the equivalent of a bike fork breaking.
e.g. What keeps bicycles balanced with or without a rider is still an active area of research, and even the seemingly basic idea that, for a bicycle to be self-stable, it needs to turn the handlebars into the fall, has not yet been proven.
>We have all the physics solved for bikes, it's a complicated system but so is everything in motion. Hence we assume a spherical cow for the sake of the problem.
This depends upon the question one is trying to answer. If one is trying to create a bicycle that can self balance, that involves considering different factors compared to trying to determine why certain injuries result in a person losing the ability to balance on a bicycle while others do not. Is the focus the bicycle or the human?
But when the bicycle is not moving, lost too is the ability to move your point of balance through steering. That alone explains how hard it is to balance when not moving.
I do not believe the wheels spinning give you even a modest assistance in balancing.
This is a very interesting video that debunks some common theories of how the bicycle balancing works, and also proposes some extra insights (although no definitive theory yet)
Bicycles are entirely stable without a rider as long as they’re moving. The human is only really necessary to provide motive power. There are a ton of videos showing this.
It is totally unlike the intentional instability of a modern jet fighter.
This is not intuitive, except with the benefit of hindsight.
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