> Even today, few bicyclists understand how a bicycle is able to turn and remain upright.
I’d go so far as to say no cyclist understands. AFAIK there’s no simple physical explanation.
I’d go so far as to say no cyclist understands. AFAIK there’s no simple physical explanation.
As you can see from the simulation, this is a multibody dynamics problem. The bicycle and human have lots of moving parts, and as they move there are forces in 3D [2] amongst them. So there can't really be a simplified, short and mostly complete English explanation (like for why planets go around the sun). That doesn't mean we can't predict.
[1] https://www.comsol.com/blogs/simulating-the-motion-of-a-self...
[2] i.e. you can't find a 2D plane in which all forces act.
> Their study shows that there isn’t one simple reason for this phenomenon. A combination of factors, including gyroscopic and caster effects, bicycle geometry, speed, and mass distribution come into play to keep an uncontrolled bicycle upright.
I think we’re saying the same thing. There is no simple physical explanation that humans can intuitively understand, because the interaction of forces is so complex. I’m not claiming that it’s a mystery causing fundamental problems for physics.
So don't say "no astrophysicist understands stellar reactions" because that is false. They understand fully, and can write the model and simulate it to answer any question.
Ditto for bicycles. Just because there is no simple explanation for bicyles does not mean we don't fully understand the physics of bicycles. It just can't be put in English. Only in complex mathematical models.
Cyclists are not exactly the equivalent of "astrophysicists" in this situation though. There are of course physicists who are also cyclists, but basically no cyclist who is not (or isn't very interested in the field) would be able to explain it.
This is probably a case where not being a scientist was an advantage. Turns out they didn't need a simulation or mathematical proof it could work in order to try it.
However, on the question at hand, it mostly says:
>Bicycle stability can’t be explained using just one or two mechanisms. It’s a combination of many different intertwined factors, like the mass distribution of individual components, size of the tires, geometry of the frame, and others. [...] 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.
There is no mention of air resistance at all. Does it play a role in (de)stabilizing the vehicle in higher speeds? Would a bicycle work as well in, say, lunar vacuum (I imagine that it would be hard to pedal in spacesuit, but let's assume a spherical cow and a lunar bicyclist in normal clothes). Would a lunar bicycle be more stable at lower speeds because of the lower gravity on the Moon?
When I started riding motorcycles, I bought a well-known motorcycling book. It had a whole chapter on countersteering because there are even today many seasoned motorcyclists who don't believe or understand that you turn using countersteering.
The actual question is "Why, when you give a bicycle a good shove, does it stay upright on its own, continually changing its direction to balance itself?"
It's well known in motorbikes that the amount of rake is what makes a bike more stable vs more responsive to steering. Some folks lower the front of the bike - tighten the triple tree lower on the forks - to increase responsiveness on otherwise more boring bikes.
Of course there's more to it all, gyroscopic effects and so on, but this is the countersteering perspective.
There's more stuff here: https://calfeedesign.com/geometry-of-bike-handling/
Back when I used to do my commute with e-scooters, indicating my direction was a real pita and, most of the time, totally impossible. In fact I used to use the sidewalk and pedestrian crossings if I needed to go left through the traffic.
Understanding the physics is not a requirement to operate the vehicle.
The rider turns the bike by moving the handle bars slightly in the opposite direction he wants to turn. Then the bike falls in the direction he wants to turn, and the handle bars are then rotated in that direction. To straighten out, the handle bars turn a little tighter, and the centrifugal force of the turn pushes the bike back upright.
Definitive explanation? Yes - to a significant degree of definitive. As with all science/engineering-understanding there are always further details but this we've got pretty well down at the macro level humans operate at.
A site beloved by HN to explain this: https://ciechanow.ski/bicycle/
A beautiful site, check out the archives for other explanations and animations of things too.