Re: [ST] Emile

["Emile Nossin" <Emile@xxxxxxxxxx>]

>From: Sprint ST
>Here I disagee. In this state they have a stupid driving test with a portion
>of weaving through cones at very low speed.  I have practiced it a lot
>watching exactly what I was doing.  There is a point where you just turn the
>bars in the direction you want to go.  This is where the steering component
>design comes in.  You have to keep the gas on so that there is forward
>momentum.  That's what's keeping the bike from falling over.   

We have to do that too, actually the exam is now two different parts
including the parking lot maneuvering part as the first. It's pretty comprehensive:
http://rijbewijs.cbr.nl/pdf/Motoroefeningen.pdf
With my own little motorcycle gang I practice these and more advanced exercises
every year when spring starts. Next Sunday it's that time again :-). At low speed
you don't need a lot of lean angle, but the leaning is certainly done with counter-
steering. Do try it out. But again, when you are in the turn, the wheel will be pointed
towards that turn. If you hardly need any lean, you are practically transitioning to
moving the wheel direction turn right away. But you'll see that you will still (in a
minimal way) use countersteering for that minimal lean.

It's certainly NOT the forward momentum that's keeping the bike from falling over.
If that would be true, you could weld the front end in a fixed forward position
without the bike falling over (with or without rider), which is not true. It's the
steering geometry (trail, rake) which, even at low speed, keeps a bike from
falling over immediately. Keeping on the gas also doesn't mean momentum,
speed would mean momentum. But both throttle nor speed are keeping a
bike upright, that's all steering geometry.

>3.) http://www.msgroup.org/TIP066.html
>This is more of the same, I believe the counter steering is more rake, trail
>and power assisted some by gyroscopic precision at the beginning but more to
>do with distortion and position of the patch and camber thrust. 

Agreed, but precession only help lean during the initial counter turn of the
handle bars, it will RESIST the leaning process that follows right after though.

>We can disagree about the theory of steering but I have not seen that they
>have proven anything.

Well, they seem to have proven that steering input has become A LOT lighter
on their bike when canceling out the precession forces. Same on the resulting
wobbles and slappers when on the quick switchbacks.

> That's way I smell snake oil when I read their stuff.
>One point they hammer that is dead wrong is about the lateral instability.
>I think everyone has seen the pictures of the bike going straight without
>the rider AFTER a high side.

Not sure what you mean here. The bike going straight means that the steering
geometry is working like it should, without it the bike would just fall down.

>Does steering become heavier in your car with speed?
>Yes it absolutely does!!!!

Well, I don't have a car but have driven all kinds. All the non-powersteered
cars I rode where VERY heavy to steer when trying to park, but were A LOT
lighter to steer on the freeway. Same on the Fokker 50, even though it's powered.
The nose wheel is very heavy to turn when trying to make a 180 in the London City
parking lot with speed near zero, but it becomes much too light and sensitive
during the take off roll, which is why we switch to using just the rudder with
speed. Your car's different?

>While the mass of the bike remains a relative constant the velocity
>increses.  Momentum is mass time velocity.  Now I'm getting into rusty
>territory, but momentum is a vector quantity.  To change that vector in the
>turn you have to apply force.  You have to add gas to maintain velocity
>because it is getting scrubbed off by the camber thrust.

All agreed to this point, keep in mind that the speed is only relative
to the observer and so is its momentum. A 747 rolls in pretty much the
same manner at low speed as it does at cruising speed, it only needs more
aileron (more force) to get the same roll rate. So at higher speed (like
with a car!) the force needed for the same roll rate is lower. The bank
angle will also be the same. And the time it takes to turn (generally
2 minutes for a 360 degree turn) is also identical. To the pilot there's
not much difference except that the steering is lighter. To the observer
though this speed has an obvious difference since the turn radius of the
747 at cruising speed increases from a city to the entire country (of the
Netherlands that is :-)). See what I mean? The 747 also needs an equal
amount of extra thrust at any speed to compensate for the extra drag (loss
of vertical lift, same thing on motorcycle sort of).

>In this process
>the bike is still trying to go straight so you have to keep applying force.

You have to apply force because the bike wants to upright itself because
of steering geometry and perhaps a bit of precession. However if there would
be no rake (no trail) the bike would not have this tendency. The speed increase
will not help to certainly upright it. First of all because the speed is (or
was) in a forward direction, the righting up is a left right vector.
Now centrifugal force (as felt from a rider without lean) could upright the
bike in a turn (that's the right direction for a vector to do that), but that's
why you are leaning. Sort of balancing between centrifugal and gravity force.

>There is lots of problems comparing cars and motorcycle steering.  When a
>car leans it usually isn't a good thing.  They don't have special front and
>rear tires. Etc, etc.  Again, without power assist I do believe steering
>does get harder with velocity in cars.

I don't think so... shouldn't matter with or without power steering actually.

>Something I did run across on the counter rotating brakes is some guy said
>that someone tried this same idea back in the 1980's or 90's.  I don't
>remember it, but he said it died from lack of interest.  

I can imagine the idea will initially be laughed at by engineers brought up
with traditional ideas, of course it does sound too easy or too good to be
true in theory. Then again I could see how mainly the complexity (and in
earlier days weight), just like with the double rotor choppers, would finish
off any early attempts. Interesting subject nonetheless...
Thanks for the brainstorm so far :-)

Emile
www.piloot.com

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