L A W S O N A W D BECAUSE THEY CAN William Lawson is a retired mechanical engineer living in Somerset, Wisconsin. His son, Martin, is an engineer who works for the University of Wisconsin, Madison, designing laser beams that measure particulate content in the earth’s atmosphere (or something that sounds like that; I wasn’t really listening). Marty had the idea for the two-wheel-drive motorcycle, and his dad had the time to build it. They felt hat true two-wheel drive hadn’t yet been given a fair shot.
The three designs that are most commonly known are
the Rokon (which has no front suspension), the Ohlins-Yamaha 2-Trac (a limited-output hydraulic system) and
the Christini (which requires considerable rear-wheel spin
before engagement). The Lawsons wanted to make a drive
system that could transmit the same amount of torque to
They did it by combining a Hossack front suspension
design with their own drive system. The Hossack front
end is what BMW uses on the R1200GS; it is sort of a
parallelogram with a single shock. Power
is transmitted from the rear sprocket to
the front wheel through a series of chains,
sprockets and U-joints. There’s nothing
mysterious about the design at all. You can look at it and
understand everything without an engineering degree.
There’s a one-way ratchet that allows the front wheel to
freewheel faster than the rear wheel, which happens, for
example, when you lock up the rear brake. A big difference between this and most other AWD systems is that
the gear ratio that drives the front wheel is about the
same as the one in the rear. On the Christini, for example,
the gear ratios are about 20 percent different, so the front
wheel is freewheeling until there’s a certain amount of
rear-wheel spin. There’s only about a 1-percent difference
on the Lawson.
The drive system in front isn’t quite as beefy as the one
in the rear. The chains are 428 (as opposed to 520 in the
rear), so to guard against the theoretical possibility of overtaxing the system, there’s an adjustable clutch in front. If
the front end is trapped while the rear wheel is free, the
clutch can slip before anything breaks.
All this was worked out in a series of seven different
prototypes. The first was on an older Yamaha TY350 trials
bike. The most recent two are a KTM 350EXC and an AJP
PR- 4. I got a chance to live with those two bikes for about
The AJP PR- 4 is an entry-level
motorcycle with a very mild motor.
Adding front-wheel drive expands
this motorcycle’s ability considerably.
A total of seven Lawson AWD motorcycles have been built. Bill
and Marty aren’t interested in offering kits, but they would like
to see their concept reach production.