Re: [ST] Emile discussion

["Emile Nossin" <Emile@xxxxxxxxxx>]

>From: Masiak, Richard
>Subject: [ST] Emile discussion

Emile discussion? I thought this was still about the counter rotating brakes?
Whatever... :-)

> http://piloot.smugmug.com/photos/21016258-L-1.jpg
>I disagree.  The low speed lean (peg dragging) turn in the pic is not done with
>countersteering IF counter steering is what I think. That is: When turning the
>bike left (at speed), the front of the front tire is pointing to the right and
>the opposite  for turning the bike left.  Countersteering, I thought, is pointing
>the wheel in the opposite direction or counter that of the turn/lean.

I don't think you understand countersteering completely. Here goes:
When turning the handlebar (and frontwheel) towards the left (at ANY speed),
the frontwheel will ride away to the left initially, where centrifugal force
will let the bike fall over the the RIGHT (it wants to go straight, but can't
since the frontwheel has gone left). That's where the name comes from, steer
left to go right.

However, the process isn't over then. Whilst the bike is falling to the right,
the precession and trail of the front wheel will turn the front wheel towards
the direction of the turn (= right!). This is a good thing, since it makes
the bike stable. If you wouldn't interfere the bike would straighten up by
itself (because of the trail, the precession is more a retarding / resisting
force, not a stabilizing one). Without this stability the bike would not be
rideable, you'd be trying to balance the bike continuously.

Once in the lean, the front wheel will be turned towards the direction
of the turn (like in the picture). That will also stop the bike from
leaning more since the fronthweel will then be trying to ride back under
the bike. The result is a turn, where the centripetal force will balance
the remainder of the gravity. Like in an airplane, the turning of the
stick or control wheel doesn't turn the airplane, it will only roll it.

>If that is true then the low speed pic has the front of the front tire
>pointing left while turning left which is not countersteering.

Again, the countersteering banks the bike. Once in the bank the front wheel
is already pointed towards the turn. To get out of the right turn, steer more
right so the bike will be flung over by centrifugal force to the left (or let
the steering geometry upright the bike by itself, where the trail actually
forces a countersteer, notice that you have to apply a bit of left steering
force (just force) in a right turn).

>I meant "just like a car" meaning like the pic.  Turning the front of the
>front tire in the same direction as the turn when going faster than the person
>in your pic.

Every bike has the front wheel turned towards the direction of the turn,
ONCE they are in the bank that is. Otherwise you wouldn't be turning (you'd
be falling). From straight up, initiating towards the desired lean angle,
the front wheel will initially be turned away from the desired turn direction
though...

>But now I understand that since presession is the force acting in opposition
>to the actual countersteer, lightening it will require less energy from us to
>countersteer but countersteering must still happen.

Sort of, yes... Precession is like mud, it resists change (and actually
applies force towards a different direction because it is delayed). It's
not a stabilizing force. A gyroscope is actually not stable in space, it
is extremely neutral. If a gyroscope changes attitude (which it usually
will because of precession caused by drag) it will not go back to its
original attitude (which would define stable). It will however strongly
resist being changed because of precession (sort of), so its really very
neutral (not unstable either).

>It is not physically possible to turn a bike by steering/pointing the
>front end of the front tire in the direction you want to go when going faster.

Well you could, by first hanging off. At higher speed you will hang off
a whole lot if you would want to turn without banking. You sort of get
the effect as a sidecar rig on the track. So if you have a little
platform next to your bike and an extra person that could hang off
another meter or so, then you could do without leaning and therefor
also without countersteering :-).
http://www.fatbaby.org/racing/images/040620_sidecar.jpg

>By cancelling the precession forces countersteering can happen with much less effort.

Yes.

Emile
www.piloot.com

_______________________________________________
Triumph Sprint ST/RS mailing list
Send list posts to ST@xxxxxxxxxxxxxx
Change your list options at www.Triumphnet.com