Leav said:[A tadpole's front] axle is not exactly on the kingpin, so any
force on the wheel axle (which would be created by braking) would
turn the wheel and affect the steering.
To which Jeff (very astutely IMHO) replied:
Quoted message said:... the kingpin's axis should intersect the ground on the same
line as the centerline of the tire. This will prevent the tire
from being steered right or left by off-center braking...
But having been officially notified now in another thread that:
Quoted message said:... experts are welcome here too provided they do not go on and
on at too great a length.
Perhaps, I too (a modest non-expert) can expand a bit:
It may help to think of braking force applied to the hub carrier
assembly (kingpin) at the tire's contact patch. If a line through
the rotational axis of the kingpin hits the center of that patch,
almost no matter what kind of other parts are in the assembly or
their 'internal' geometry, then the braking force will ultimately
have almost no 'lever arm' to cause the kingpin to turn and steer
the trike.
FWIW: There's a bit of highly technical design and jargon in the
science (and art) of steering with a two-wheeled 'axle', most of
which is of almost no relevance to most tadpole riders. E.g.,
the tire's contact patch is really usually slightly behind the
kingpin's ground reference point, (which most folks think of as
'trail'😉 to enhance high speed stability.
Most newer tadpole designs also have the tread contact patch
located just inboard of the kingpin's ground reference point, so
that single-sided braking actually applies a small intentional
force toward rotating the kingpin away from the braking side.
For example, if you apply only the right side brake, this force
would try to steer the trike to the left. But braking on one
wheel to the right of the trike's center of gravity also creates
a couple (or moment) on the trike as a whole ('body' or mass)
that tries to make it turn to the right. If this steering design
(called ABC for Asymmetrical Brake Compensation on the LoGo
trikes) is done well, the end result will be that the two forces
almost exactly balance, and the trike shows almost no tendency
to pull to the side, even under very heavy one-sided braking.
The design tradeoffs for ABC are relatively trivial, and most
trikeys who've ridden a tadpole with this design love its added
safety and convenience.
Regards,
Wayne
