Jeff Grippe wrote:

I don't know about the science behind this but the idea matches my
experience on the trikes that I've owned. Everything is fine under 25 mph.
Even the top heavy Tricruiser is fine at that speed. At somewhere between 25
and 30, however, something happens and the steering characteristics change.
Under normal riding conditions you constantly make minor steering
adjustments to keep moving in whatever direction you are going. The side
effects of these minor adjustments is magnified by speed and then further
magnified by braking.

Steering side effects are often /less/ at higher speed (which is why you
wobble at very low speed). The forward momentum takes you a lot further
along compared to any sideways motion, with the net effect of going
straighter.

Typically any adjustments can be made practically subconsciously if one
can relax on the job: the less one relaxes, the less easy the steering
is. Trikes certainly don't necessarily come unstable at 25-30,
velomobiles routinely travel at those sorts of speeds over significant
proportions of their journeys.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/