Comment by beardyw

Comment by beardyw 4 days ago

11 replies

> Bicycles achieve balance through the gyroscopic effect

No they don't. If that were true you could cycle along at a 45 degree angle. They balance because you steer into a fall.

Levitating 4 days ago

> They balance because you steer into a fall.

They naturally steer themselves into a fall really.

ajmurmann 4 days ago

Wouldn't that imply that a bicycle wheel I roll down the street by itself should fall over immediately which clearly is not the case?

  • aidenn0 4 days ago

    There's not zero gyroscopic force, just negligible compared to the moment of inertia (with the tyre/ground interface as the axis of rotation) of the bike/rider system.

    Furthermore you will notice a bicycle wheel rolling down the street often won't roll in a straight line (as it starts to tilt sideways, it will turn to bring the contact patch back underneath it), so even with just the wheel, the gyroscopic stabilization is insufficient on its own to keep it upright.

  • powersnail 4 days ago

    A bicycle is not the same as a bicycle wheel though. I can't just roll down a bike down the street (at least not as easily as a single wheel); it almost always immediately falls over.

    • bityard 4 days ago

      Sure you can.

      At very low speeds, yes, the bike will fall over. But a bike with some minimum amount of speed can roll upright on its own just fine. You can try it yourself with your least favorite bike and an empty parking lot. All it takes is a good solid push. It has to do with bicycle frame geometry and center of mass.

      Neil deGrasse Tyson explains it in this video at 2:52: https://www.youtube.com/watch?v=RIrgwWQqqts

      • Gh0stRAT 4 days ago

        That's not countering the argument that steering is what is preventing the bike from falling over rather than the gyroscopic effect of the wheels. You'd have to tie off the handlebars with a static line before rolling it in order to prove that it was the gyroscopic effect keeping the bike upright.

      • powersnail 4 days ago

        I actually tried a it a lot when I was young, and it never worked even on a downward slope. Maybe I was too weak back then, but again, the point is that a full bicycle doesn't have the same behavior as a standalone wheel, which is very easy to roll, and pretty much stands on its own until its speed is really really low.

pengaru 4 days ago

It boggles the mind how much people believe gyroscopic forces are what keep bicycles and motorcycles upright. It's even taught in text books.

It only really enters the picture during wheelies, if you've got the front wheel spinning fast enough.