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From: toddv@copper.UUCP (Todd Vierheller)
Newsgroups: net.cycle
Subject: Re: Re: Need classroom demonstration gyrosc
Message-ID: <279@copper.UUCP>
Date: Mon, 14-Apr-86 11:43:18 EST
Article-I.D.: copper.279
Posted: Mon Apr 14 11:43:18 1986
Date-Received: Thu, 17-Apr-86 04:46:54 EST
References: <562@kepler.UUCP> <800011@convexs> <329@tolerant.UUCP>
Organization: Tektronix, Inc., Beaverton, OR
Lines: 67
Summary: Countersteering/Gyrospope/Putdowns

I really don't care why countersteering works.  (I know why and so does
K<bob>.)  My complaint concerns the spirit of a reply.  K<bob> showed
no antagonism, yet he came under attack by R. Beaver.

K<bob>'s comments are preceeded by a ">".
R. Beaver's comments are preceeded by a ">>".

> Um, what do gyroscopes have to do with countersteering?
> Countersteering is not related to precession.

> Consider a bicycle going slowly.  At a speed of 5 MPH or less, the
> precessional forces generated by a pound or so of bicycle wheel are
> just a few ounces, but a 200 lb. bike+rider combination can be
> effectively countersteered.  (Probably heavier ones too, but that's
> all I weigh.  :-)

Note above, the argument based on *physics*.
  
> Then how does countersteering work?  When the bars are turned to one side,
> the front wheel moves IN THE DIRECTION IT IS POINTED.  The bike above it
> doesn't.  So shortly, when the wheel is no longer under the bike's center
> of mass, the bike starts to tilt, IN THE OPPOSITE DIRECTION.  Then the
> rider who doesn't want to fall over points the wheel into the turn to
> stop tilting.
>					K<bob>

Again, a clear explanation with the underlying physics too obvious to mention.

>> You obviously don't understand.  You certainly need a MSF refresher course
>> or or an introductory course to physics.
 
Beaver's above comment is unwarranted.  It's purpose is only to put down the
original poster in order to elevate the writer.  (And it's incorrect.)

>> Countersteering is related to physics, not "precession[?]".  

Precession: a comparatively slow gyration of the rotation axis of a spinning
body about another line intersecting it so as to describe a cone caused by the
application of a torque tending to change the direction of the rotation axis.

>> Please take an MSF course.  The origional poster of 
>> this article knows what he needs and you need him.

Again unwarranted.  K<bob> did not earn any abuse.

>> --beaver
>> {allegra!oliveb, seismo!mordor, ihnp4!nsc, ucbvax}![IN]tolerant!beaver

Countersteering works the way K<bob> explained it.  Bicyclists use the
technique to *swerve suddenly*.  (Leaning is adequate on a bicycle in most other
situations.)  On a bicycle one turns the wheel hard left (without leaning into
it.)  This causes the bicycle to *fall* right.  Then, the bicyclist turns
hard right to correct for this fall.  Voila! Countersteering.  To initiate a
hard turn (swerve) on a bicycle, turn the wrong way first.
Why use a bicycle in the argument?  Because the gyroscopic forces are too small
to account for the *quick* change of direction of a much larger mass (the
bicycle and rider).  F=ma (the "a" includes the time aspect).  The gyroscopic
effect would produce a slower change (if any) and cannot account for the
observed results.

Motorcycles (being heavier and resisting the lean of the riders weight)
respond better to to countersteering in a much larger domain of conditions.


                                   Todd Vierheller
                                   Tektronix, Inc
                                   Portland, Oregon