My KS-14D wiggles when going fast and straight

[Smoother]

4 hours ago, Rehab1 said:

Definately with speed. I am trying to figure out what piece of equipment could be modified to accurately perform this task. The wheel would need to be be held statically in a fixture during the run up/ balance test . You could then  use stick on weights on the hub to balance the wheel.  

I'm going to test the balance of my 14" right now.  I'll just assemble it without the motor inside the wheel and give it a spin.  Without the magnet/coil interaction, it should freewheel nicely. I'll use the old bearings because they are grease and dust-shield free, so they should be really free spinning as well.

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EDIT  20 minutes later, after hammering the old bearing back into the motor shells and clamping the rim/tire assembly in-between, an out of balance tire is the least of my concerns. 

Running the wheel up to speed by holding the axle ends, pushing it across the ground (like a trim wheel exercise device) and then lifting it, even at a relatively low speed, any yaw in the axle plane creates a pronounced gyroscopic turn in the same direction.  So if you're riding, and alternate pressure between your feet, the wheel will not just tip sideways, it will turn in the direction that you pressed down on. i.e. when you push the right side down, the wheel will lean right, AND twist to the right too!  Now obviously when you add in the rest of the weight associated with riding a complete rig, the gyroscopic effect is quashed to some extent, but it's still there.

My 2.5" tire is probably twice as heavy as the 2.125" factory tire, and this weight is at the outermost edge of the rotating mass; so it amplifies the gyroscopic effect.  This would explain why, when I lean to one side, the wheel tries to turn markedly in that direction.  I thought it was a function of tire profile, or pressure.  Now I understand what's going on. And the faster the wheel turns, the stronger the effect.

I'm seeing how a wobble develops from this gyroscopic turning; if one alternates pressure between the pedals, say by running over an irregularity in the road, the turning begins.  Add in the changing interaction between the tire and the road surface, and I suppose it might get worse.  I'll try and make a video.

[Smoother]

Sorry about the focus, and the lighting, and the dialogue, and the set, and music score, and, and, and.  But here it is.  I'm only tipping the axle up and down.  The turning is entirely due to the gyroscopic effect.

[Rehab1]

23 minutes ago, Smoother said:

Sorry about the focus, and the lighting, and the dialogue, and the set, and music score, and, and, and.  But here it is.  I'm only tipping the axle up and down.  The turning is entirely due to the gyroscopic effect.

Yes that is gyroscopic precession which is basically a phenomenon occuring in rotating bodies in which an applied force is manifested 90 degrees larer in the direction of rotation from where the force was applied. Inventors of helicopters had to take this into consideration before  the aircraft could fly safely.

 

 

[Rehab1]

5 hours ago, The Fat Unicyclist said:

Have you seen this... 

 

Thanks buddy! I just read his technique and gave him a . Certainly makes alot of sense. Special thanks to  @mrelwood wherever you are!

[Smoother]

2 hours ago, Rehab1 said:

Inventors of helicopters had to take this into consideration before  the aircraft could fly safely.

 

Well they didn't succeed, at least in that helicopters are not inherently safe, now are they.  Thanks to your video link on gyroscopic precession, I've been watching Walter Lewin college lectures (MIT I think). on this, and the next one in on Electromagnetic Induction, Faraday's Law, and Lenz Law.  That can't possibly be helpful.