Balance and point of contact

[John A Peters]

Balance and point of contact

When the point of contact is centered under that wheel the wheel is balanced and it is less likely to wobble. Both acceleration and breaking move the point of contact off-center and out of balance making wobbling more likely. 

Out of calibration may have an affect too. Low mounted batteries help stabilize the wheel.  If a unicycle was weighted like a Russian doll, I don't think wobbles would even be possible.

Stay loose (No grip) most of the time and use a grip in case of wobbles.  Or grip and sit. 
 

What do you think?

[conecones]

Based on my personal experience, I prefer a solid connection between legs/feet to the wheel (locked in), but separate the leg motion from the upper body.

Imagine a skier slaloming down a hill, their legs are constantly twisting left and right but the upper body remains straight. 
 

I find this allows more aggressive riding without committing my centre of gravity too heavily in any one direction (so that recovering from bumps, loss of traction,etc) is easier.

[John A Peters]

Balanced Point of Contacts

My theory is that when the center of gravity (the axel) is centered over the  point of contact with the road, the wheel is balanced and it is unlikely that a bump will cause a wobble.  When the wheel is not balanced and there is an offset, there is a much greater likelihood of a caster effect or a wobble. This is true for both accelerating and braking. The difference is that when accelerating it is relatively easy to do a mini carve or a turn. whereas when braking it is harder to do a carve or turn since the rider may be in a semi emergency mode.

Right now I am only studying the effects of an offset between the two points with respect to the need to be on top of your game. I am not interested in ways to eliminate or counteract wobble or how to ride safely. 

Do you agree that when the CG and the tire contact point are offset that there is a greater chance for a wobble and less of a chance for a problem when the two points are lined up vertically?

 

[Tawpie]

I had to read this a few times carefully because my first reaction is that I am pretty sure I've never wobbled unless I was moving, and movement requires my CG to be forward of the axel. But I think you may be referring to having your CG out of alignment side-to-side? Then I'm certain a bump can incite a wobble because it happens to me when I go off little jumpletts in the path... I tend to land a bit harder on my dominant leg and the wheel wants to swerve. It doesn't really wobble, but it does require correction and since my control system is a tad underdamped it could easily degenerate into a full blown wobble.

Nevertheless, I think precession has more to do with speed wobbles when you're not hitting bumps in the road.

For me, braking wobbles were solved by forcing my left heel into the pedal and s*itting rather than leaning backwards... I was probably unbalanced side to side and that 'left heel DOWN thought' helps me even things out. So you probably have something. I've never feared wobbles while accelerating... only while cruising too fast on tired legs and (until I figured out the left heel and body position things) during very very hard braking.

[UniVehje]

Wobbles tend to go down with kilometres ridden without any change in CG. It’s mostly about riding muscles getting stronger and improving riding technique. No experienced rider think about wobbles as they don’t really happen anymore. Only hard braking might still cause them but that’s just because it is rarely practiced. Trying to find reasons from wheels seems to be futile. 

[Zopper]

@UniVehje I mostly agree, except that experienced riders don’t get them.

They can get them too, it’s just much rarer and usually accompanied/caused by factors like cold weather, tiredness and so on - stuff that limits the control of muscles, stuff that makes you ride more stiffly. And of course, these riders are much more likely to stop wobbles in the beginning by a changing something in the ride without even thinking about it, so they disappear quickly. 

[Zopper]

@John A Peters You are getting it the other way around, I think. Braking (or accelerating) doesn’t move CoG (of you + the wheel) away from the contact patch. By moving CoG away, you induce it. And the moment the wheel starts applying a torque in either direction, the forces begin to equalize until the CoG is effectively above the contact patch again, after accounting for the change of “down” vector caused by acceleration. And this happens many times per second.

The problem of wobbles is in your body and mind, in getting into a resonance when your muscles try to compensate and end up overcompensating. And the simplest way to get out of it is usually to force a turn (even a very large diameter one, carving, etc.) the moment you feel the wheel doing zig-zag-zig.

[Singasong]

So you wonder about how much mental attention needs to be paid in regard to different riding techniques?  I find on pavement, I can simply tilt my head and my body leans over with the wheel away from my cg, like a diagonal line. You can shut your mind right off, as long as your body is relaxed, weight is on outside of the feet and you look ahead. Normal bumps (not potholes) dont faze the wheel if you don't stare at them. If I use the upright stance with feet turning, rather than body leaning , the wheel stays under you and legs lightly grip thr wheel. This requires way more mental acuity and physical effort, but is quicker reacting and less likely to send you off on a big bump. The key ti both is looking ahead, your brain deals with a shifting cg really well on its own if you leave it to its own devices. 

[John A Peters]

2 hours ago, Zopper said:

@John A Peters You are getting it the other way around, I think. Braking (or accelerating) doesn’t move CoG (of you + the wheel) away from the contact patch. 

On the contrary this video shows an exaggerated shift of the two points.

https://www.youtube.com/watch?v=8hFlY19sj9I&ucbcb=1

Edited August 10, 2021 by John A Peters

[Aztek]

On 8/8/2021 at 10:35 PM, John A Peters said:

Stay loose (No grip) most of the time and use a grip in case of wobbles.  Or grip and sit. 

I find that I stop it from wobbling by easing the grip. Just spread the knees to the sides and the wobble is no more.

[Zopper]

On 8/10/2021 at 7:16 PM, John A Peters said:

On the contrary this video shows an exaggerated shift of the two points.

https://www.youtube.com/watch?v=8hFlY19sj9I&ucbcb=1

It doesn’t. The center of gravity (of EUC+rider!) is still above/in front of the contact patch. The moment COG moves behind the point of contact, you either brake (if you turn the wheel with you) or you fall on your bum (if you bend your knee and keep pressing on the toes). That’s the basic mechanics of controlling EUC. It is a balancing device, nothing more. It tries to balance the COG above the contact patch. You simply can’t have COG behind the contact patch and keep accelerating without an immediate fall.