Racing Lawnmowers

[mudnut]

Many, many moons ago, as a bit of fun, I built one for the local fairs first races. It was a 12hp B&S rear engine Greenfields, with the biggest primary pulley I could fit under the body. It got around 40kph.

The next year I got into it a bit more and bought a Honda four cylinder CB 400 in bits for $100. After rebuilding it, I crammed that under the Greenfields with a suicide gear shift (hand shift with lever clutch). A mate's son drove it, but its centre of gravity was way too high to be competitive.

Third year I got the foot pedals (clutch and gearshift) working on another old Greenfields with the 400 rammed into it. The rear end used the stub axles and drum brakes from the front end of an old suzuki swift. The front wheels were pressed steel halves ones that were bolted together. I had to weld them up to comply with the regs.

I built it with four Holden 12v ignition coils. Combined with its four carbies, that thing could get from zero to 90ks and back to zero in just over 140metres. Never got it out of 4th gear and it had two more to go!

After its first test run, it had bent the steel 20 x 50 RHS chassis. I welded another rail to each side and used that as the exhausts. It never ran long enough to get red hot so it worked fine.