What was wrong with the original?

[Deleted member 4366]

The rake affects the self-centring of the handlebars. It can provide a positive centring force, where you have to provide a bit of effort to turn the bars, or a negative force, where you have to provide a small force to hold the bars straight. Turning the bars when the bike is rolling makes the front wheel precess (lean) in the opposite direction, so it has an affect on stability.

In order to make the bike lean when rolling, the front wheel has to precess, which means it needs a force in the direction that the handlebars turn. Gravity doesn't work in that direction, so it's resisted by this gyroscopic effect. It would make the handlebars turn in the opposite direction, i,e, when the bike falls to the left, the bars would try and turn to the right. If you hold the bars straight, you therefore can resist the precession, so it's a bit like tight-rope walking with a long pole. It has a basic level of stability, which you can easily maintain with very small forces to balance. The rotating wheel provides the inertia. The higher the rotational inertia, the more force you need to make the bike tilt, and if you provide enough inertia, it won't tilt with a significant sideways force, like he demonstrates in the video.. The guy that wrote that paper you linked to above, didn't seem to grasp this basic principle. Even after he'd done all his tests and calculations, he was still confused. To keep a bike upright when it's rolling, you only have to stop the wheel from precessing by holding the bars straight.

Using that Gyrobike will be like learning to tight-rope walk. A normal bike would be like having a medium length pole, but the Gyrobike would be like having a very long pole, which makes it easier. The one thing it can't stop is that fact that turning the handlebars will make the bike precess (lean over) in the opposite direction. Presumably the kid has used wheeled devices with more than two wheels before, where the steering force is in the opposite direction and larger, so you can see him still trying to yank on the bars, which immediately makes him topple. He'd probably be able to ride it better no hands.

For my project when I did my mechanical engineering degree, I studied and wrote a paper on the aerodynamics of the boomerang. Many of the effects are the same.

 

[flecc]

Gyroscopic forces generated by rotating front wheels do have an effect and a good example of how greatly they can resist steering change is in Moto GP racing etc. For fast circuits with few bends where stability at speed is the priority, a larger diameter front wheel is fitted. For twisty slower circuits where fast steering changes are needed, a smaller diameter front wheel is fitted to reduce the gyroscopic force.

The forces will be smaller on bike wheels travelling at lower speeds, but they are still present and very real.

 

[neptune]

http://www.engadget.com/2011/04/15/scientists-unlock-the-secrets-of-bike-stability-make-riders-opt

@flecc.Don`t forget that by changing front wheel size, you inevitably change steering geometry- larger front wheel equals more trail {i think]. The link above shows some interesting experiments.

In one of my earlier links, the author points out that any force applied to a bicycle at hub level is at a mechanical disadvantage as regards pushing a bike from a leaning attitude to an upright one, and for me, that is significant.

Everything I have said, I have been at pains to point out that it my opinion, and not necessarily shared by others. I feel that this a problem that is more complex than it would seem. The likely answer to the question "does gyroscopic force balance a bicycle" is "A bit"

 

[Deleted member 4366]

The likely answer to the question "does gyroscopic force balance a bicycle" is "A bit"

It's not a bit. It's a lot. You wouldn't be able to stay upright without it. You can stay upright easily on a rolling road when you have no actual forward motion, so it's nothing to do with forward momentum, but try and stay upright on a single ice skate at speed, where there's no gyroscope. You'll note that skaters that can do that have to put their arms out to balance, just like standing on a tight-rope. They have to push against the inertia of their arms to balance.

It's all to do with Flemming's right hand rule. Once you've figured how that works, it'll make more sense. Without it, you'd fall off and there would be no bicycles.

There's quite a good video here that explains it quite well, if you can stick with it to the end.

 

[neptune]

Here is another point of view, Check out the two videos in the article.

http://sciencequestionswithchris.wordpress.com/2013/04/18/what-keeps-a-bicycle-balanced/

 

[trex]

how much gyroscopic effect contributes to keeping the bike upright?
to answer that question, ride a 12" wheel e-bike/motobike at 15mph and a 700C wheel bike at 5mph. Both give about the same gyroscopic effect but the forward momentum is very different at 15mph against 5mph.

 

[Alan Quay]

How much of a gyroscopic effect is present here?

 

[Deleted member 4366]

Jeez, you're hard work. I guess it's a bit like quantum theory or relativity. Some get it, but most don't.

One last thing that might help you. Think about a bicycle wheel on its own. If you roll it down a hill, it stays upright. It has no caster, no trail, no rake and no steering head, so what stops it from toppling?

Personally, I'm not sure that what those guys did in their experiment proved anything. If they had run a counter-rotating hoop inside the wheel, I think it would have been conclusive, like the other guy found with his hoop, which immediately fell over, but their two wheels were one above the other so that the top one needs to move twice as far when tilting. Thus, it needs to accelerate faster, which means a higher force. Therefore there's still a net force that causes the precession.

 

[MikeyBikey]

Lit Motors C1 motorbike uses two, presumably contra-rotating, horizontal flywheels to balance it.

Could 2 horizontal, electric-driven, water-filled tyres, bicycle wheels keep a bicycle & rider upright? (If they could take the forces!).
And could two vertical flywheels do the same thing, or would they resist steering rotation of bike?
Last, would the flywheel power come out of the 250W limit?
Just wondering...

 

[Artstu]

How to teach a child to ride a bike
http://www.bikeradar.com/beginners/news/article/how-to-teach-a-child-to-cycle-in-30-minutes-37033/

 

[Deleted member 4366]

Surfing the links further down, I found this video that explains how you steer a bike. It's about motorcycles, but bicycles are the same. I didn't realise that by leaning with your hands off the bars, you're still counter-steering, but here's the proof.

This one shows what happens when you turn a bicycle. You can clearly see the counter-steering to initiate the turn: