Sorry to derail the thread with my tractor talk but I'm proud of it so here it goes!
I shouldn't make it sound like I designed the tractor from scratch as it is Version 3 based from two previous tractors and much of what you see is based on those tractors. Actually, it would be great if TaylorSK8 could chime in as he had a major part of designing Version 1 and 2.
The tractor used 3 16hp Briggs and Stratton engines (Everyone has to use the same engine but the number of engines is open) which was hook with a single belt run a CVT. The engine number and layout was a legacy design that a friend came up with as part of the judging was on serviceability and as the previous tractors were hydrostatic driven, this meant the only wear item was one belt. This year we went with a CVT so we had two belts but we were trying to save weight.
As we could get the front tires in the air during the pulls, each rear tire has it's own brake so we could steer down the track. And with how the actual steering was designed, we could pivot on one back tire as part of the competition was based on maneuverability.
Outside of the CVT, other major changes this year were a bolt together aluminum frame with no welding (as we learned the judges didn't like welds due to high manufacture costs). This year we added a hood to cover the engines for extra noise suppression (another judged item) and that's pretty much the basics. The tractors had to weigh less than 800lb.
Here are a few pics showing the maneuverability course, the hood open, and some of the insides.
PS. The Quarter Scale team is always looking for sponsors if anyone is interested as the funding is raised by the team to build the tractor and go to the competition.

As far as I know, we're the only Canadian team taking on the Americans (but I have since checked and there are a few more Canadians down there, woo!). The year previous to this, we got 5th out of 27 teams and that is why we have a 5 on the side of our tractor.