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Cossack Owners Club |
Written by: Peter Ballard
REFERS TO SINGLE WHEEL DRIVE UK SETUP. (RHD, CHAIR ON LEFT -
ALL DIMENSIONS INCHES
At constant
speed on a normally cambered road (slopes a little down to the left) the outfit
should pull straight at constant speed. If not, it can be adjusted to do so, but
it will take you quite a few iterations until you get it to your satisfaction.
THERE ARE TWO MAJOR ADJUSTMENTS
Sidecar wheel toe-in - the sidecar wheel should not be
parallel to the bike track, but it should try to follow a path that would
converge on the path of the bike if rolled forwards. The toe-in of the sidecar
wheel will push the outfit to the right. The toe-in is usually measured over the
length of the bike; so if you get two long straight planks of wood and push one
against the outside of the bike tyres and the other flush against the outside of
the sidecar tyre (on two bricks often helps this) then the difference in
distance between the planks measured at the rear wheel and the front wheel will
be the toe-in. But there are various controls and limits on this:
As the lead of the sidecar wheel over the rear wheel
increases, the effect of toe-in increases. However this 'lead' is not usually
adjustable, it is certainly fixed on all Russian St Ukrainian chairs (unless you
want to cut and weld). A short lead of 6" will tend to cause the rear wheel to
lift (dangerous) on right-handers under deceleration. A large lead of 18" will
cause sidecar wheel scrub at slow speeds in either direction. A lead of 9" to
12" is normal and a good compromise.
A big diameter sidecar wheel (18" or 19") will result in a
bigger contact patch for the tyre and thus the tyre will provide more 'push' if
toed-in compared with a small (8" or 10") wheel (of similar tyre widths).
As the sidecar wheel toe-in is increased over a certain
amount, the sidecar wheel drag and tyre wear starts to increase and negates any
expected beneficial effect of toe-in. A heavy chair will make any toe-in more
effective, which more or less compensates for the chair being heavy. Range of
toe-in adjustment - big wheels from 1" to 2", small wheels from 1" to 3".
Bike lean-out - away from the sidecar. Lean-out is
measured with the outfit normally laden, including people. Lean-out results in
the bike trying to turn right away from the chair, thus counteracting the pull
of the chair that would make the outfit turn left. But again there are various
controls and limits on this.
Lean-out is of most effect if the steering trail (see below)
is large, which is unfortunate since we also strive for a short steering trail.
If the chair is light and the bike is heavy, then more bike
lean-out will increase the likelihood of the sidecar wheel lifting on
left-handers. Thus with this combination use more sidecar lead and less
lean-out. Range of bike lean-out usually from zero to 3 degrees, but 5 degrees
absolute max.
RECOMMENDATIONS
Big bike with light chair - Go for max sidecar lead, max
toe-in, only then try lean out from vertical - minimises lift of sidecar on
left-handers.
Bike with heavy chair - Go for average lead, max lean out and
average toe-in - minimises sidecar tyre scrub and drag.
Definition - Steering Trail - the distance on the ground
between where the steering axis hits the ground and the centre of the front tyre
contact patch. Noting that the contact patch centroid (or centre of area) moves
rearwards as speed increases.
Sidecar Fork Trail - Measured with the outfit laden - sidecar
fork trail is typically 1/2" to 2".
Solo Trail - typically 3" to 6" to give handling
characteristics required:
NOTES WITH RESPECT TO VARYING LOADS ON THE OUTFIT
If you carry a pillion this will depress the bike's rear
suspension and will make the bike lean out more, thus pulling away from the
chair.
If you load up the sidecar this will mainly depress the
sidecar suspension and reduce the bike lean-out, but will make any sidecar wheel
toe-in more effective.
With an unsprung sidecar wheel (like in the old days when the
body was sprung on the chassis) then weight in the sidecar will only depress the
bike rear suspension, resulting in less pull to the left.