Trike Front End Design and Adjustment


This certainly does NOT apply to our "centre point" or "zero scrub radius" steering!
MY definition of this type of steering is that the projected axis of the kingpin will go through the centre of the contact patch of the tyre in FRONT view.
This means that when the front wheel hits a bump, there is no torque reaction on the handle bars, and likewise when one wheel brakes, again there is no torque reaction in the steering system.
However, when viewed from the SIDE, the projected kingpin axis is some distance in front of the contact patch, in much the same way that the projected fork axis is some distance ahead of the centre of the tyre contact patch on most bikes.
This distance, commonly know as trail with bikes, or as caster in cars, which do not normally have an offset, is what gives the feeling of "weight" to the steering while cornering at *some speed*.
As I designed my own car, and a number of road race side car outfits before I started on trikes, I was acutely aware of the relationships between steering "feel" and steering geometry.
Thus, because the trikes are a fraction of the weight of cars, the trike trail or caster was carefully designed to give a good "feel" on the road, so one can sense, for instance, exactly HOW much grip the tyres have on the road, so you can adjust your speed accordingly.
IF you were to have ZERO caster and trail, then you would have "power steering" as Bob suggests, and there would be no feel to the steering.



Thursday, 29 January 2009