Re: [ST] Emile

["Emile Nossin" <Emile@xxxxxxxxxx>]

>From: sprint_st@xxxxxxxxxxx
>Emile,
>After reading your response several times, I'm not sure we were talking
>apples to apples.  The references below explain the same topics very well.
>1.) http://www.msgroup.org/TIP048.html

I know these articles very well, have read them years ago. I have learned
quite a lot of them, but after discussing and reading about certain issues
I've also learned that James has a lot of errors and misassumptions in
several discussions. He's not the only one, there are a lot of countersteer
articles that show they don't grasp the full theory behind it.

The first article you mention already has one error, well at least one
I think is in error. I discussed countersteering and precession a couple
of years ago with a US motorcycle accident engineer / specialist who told
me precession is only responsible for 9% or so (a small number, can't recall
the exact number anymore) of the tilting action during countersteer input.
James puts it at 80% influence though. You know that that is bullocks because
this counterrotating bike makes steering easier without precession, not
harder. That's because precession helps (a tiny bit) when giving the
input, but then resists the lean change once the bike starts falling.

> 2.) http://www.msgroup.org/forums/mtt/topic.asp?TOPIC_ID=76

This article is also not very convincing. It states (like article 1) that
below 6mph you can't countersteer because there is not enough centrifugal
force. Still, just try to walk next to your bike on the left and suddenly
make a turn with the handlebars to the right. The bike will fall towards
you. Same with the mentioned "centerstand on L/R slope" trick. By walking
or standing next to the bike you can much easier filter out the rider
induced corrections (weight shifting at low speed influences lean).

>3.) http://www.msgroup.org/TIP066.html

Same error in this article, at least that's my opinion. Even if precession
would have such a huge influence in HELPING the roll, it would make no sense.
Turn the front wheel left and the precession will be directed for a right
roll. But at the instant your left steering input has stopped changing (so
when the handlebar is say pointed 5 degrees to the left) precession would
stop as well (because it's a result of a force which has then stopped).
While the bike is falling to the right precession will come in again
though. Since precession acts 90 degrees further down the wheel, the
result would RESIST the leaning / falling process. For both the front
and rear wheel the gravity influence will result in a force trying
to yaw the wheels to the right (clockwise seen from above). Since the
rearwheel can't rotate it will not do much, the front wheel wants to
turn to the right though. That will not help a lean to the right, in
fact it will help stabilize the bike to an upright position. So number
three is also incorrect...

>I'm not sure if you buy everything the counter rotating  brake guys are
>selling but I don't.

So far I haven't found as much BS as in James' countersteer articles. :-)
On top of that they have already proven their theory in practice with
that bike, although I would like to rear a lot more about it.

>The linkage you have between weight and arm is a torque not the mass times
>velocity momentum that I was speaking of.

But the velocity is only relative to an observer that's not on the bike.
For that observer the turn will always increase with speed, but for the
rider the input and lean would be the same (if you remove precession).
Imagine you'd be able to ride (more like slide), just theoretical for
the sake of discussion, with your wheels not turning (like sliding over
ice) with high velocity. There's no precession, why would steering
become heavier. Does steering become heavier in your car with speed?

>The explanation of camber thrust covers what I was talking about where
>there is much more momentum and force to deal with by the contact patch
>as the speed increases.  That is why a think that the rate you can dump
>lean into the equation isn't the whole story.

Why is there more force involved? Wouldn't your same theory apply to
cars as well then (and not make sense)? 

>But I think I'm just going to jump on the Sprint, tug on the bars and
>let God get me around the corners :-) Rod

Nice idea, don't bet on it though ;-). May the magical turning force
be with you!

Emile
www.piloot.com

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