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Re: Motorcycle steering



To add a few more cents to the motorcycle (m/c) element, here are a few
numbers for my old m/c:

When I wrecked my Honda CM400 the first time :^( I bent a front fork tube
and replaced it, hammering the bits flat in the Purdue Physics machine
shop before re-assembly.  At that time I collected a little data on this
problem.  

My front wheel massed 17kg, and had a diameter of 0.7m.  I'd guess that the
rear wheel probably massed 20% more -- about 20 kg.  At 62 mph (100 km/h) 
and a combined rider-cycle mass of about 275kg I get the following:

v = 27.8 m/s; omega = 79 rad/s
Ifront = 2.1 kg m^2; Itotal = 4.5 kg m^2; 
Lfront = 165 kg m^2 rad/sec; 
Ltotal =  525 kg m^2 rad/sec;
KErot = 1430 J
KEtrans = 10600 J

It'd be interesting to compare these to figures for a bicycle at 30-40 mph,
and to a larger m/c at significant speed.

I would also like to point out that my motorcycle handled quite differently
at lower vs higher speeds.  At low speeds it was very easy to wrench the
vehicle about and turn by steering where I wanted to go or just changing 
weight distribution or leaning.   However, at high speeds
quick steering REQUIRED countersteering, and the m/c was extremely resistant
to changes in attitude (very stable).  I notice that larger cycles countersteer
from rest (at low speeds) and I think the great disparity betwwen moments
of inertia for bicycles and m/cs means the countersteering phenomenon 
is much more notable with motorcycles.  Countersteering is different even 
amongst small vs large m/cs.

Anyways, I hope to find out soon about the handling characteristics of 
larger cycles by buying one; my wife gave my old CM400 away to a student
she didn't like :^).  Now that spring is coming, I intend to buy a new
used m/c.

Dan M

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
danmac@nau.edu  http://www.phy.nau.edu/~danmac/homepage.html