There is very little ground clearance built in, only around 2 inches. I would argue this is too little (bottoming out over bumps is painful and very bad for handling), but I was vetoed in the design phase. The big news though is how much more compact this car is from its predecessor. It made packaging a lot tougher, but the payoff in weight is worth it.
One of my favorite parts of the car is the swaybars. On previous cars, they were bolted into weird spots, always as an afterthought. However as the car progressed our original ideas for swaybar mounts became impossible. Originally, they were to be run through a pair of pillowblock bearings bolted to tabs welded on the underside of the roll bar support tubes. However this would fail the cockpit template test. So we decided to just run the swaybar through the front bulkhead tube instead! The links only had to be a little longer and by ditching the pillowblocks and tabs for delrin bushings, we shaved a bit of weight as well. Plus it looks badass.
In the rear, the engine mounts got in the way of our proposed swaybar mounts, so we just ran the swaybar through the support tube below the engine (you can see the ends of the swaybar poking out just below the front lower control arm mounts). Genius! For the rear, this put the linkage in a perfectly straight line from the rocker to the swaybar, making the swaybar more effective. You can also see how the damper mounts double as engine mounts (though the engine is not in the car). No, your eyes do not deceive you, they are offset. The axles used were originally from when our cars were YFZ450 powered. The sprocket offset on the GSXR is different. Custom axle half shafts are crazy expensive, so we had to reuse axles and thus offset the engine slightly to the left. It’s not ideal, but we made it work. Check out the beefy mounting blocks for the diff, with turnbuckle upper mounts to properly set chain tension. The diff is from a TRX300 and is a clutch type LSD, housed in a custom made aluminum case that also mounts the sprocket. Since the diff came out of the front axle of a TRX300 ATV, it is shaft driven, so the case not only shaves weight, but also allows the mounting of a sprocket for chain drive. Hopefully in the next iteration of diff design, the team can ditch the cast iron diff cage inside all of this and cut off another 4 or 5 lbs.
Here’s the diff up close. Teams with money can afford a nice, $3,000 custom made diff with loads of adjustment. We built this by re-casing a TRX300 diff. The steel sprocket is from McMaster Carr and was hogged out to fit the case. It’s heavy, but won’t fail (this is a relatively common occurrence in SAE, as it is easy to go wild and hog out too much material and have your sprocket explode under a hard launch). There is still a lot of weight to be saved here, but in the interest of time and cost, we reused the diff from 2012. The uprights were new to fit the new chassis design. This diff case took a few weeks to make due to needing both a mill and lathe, which aren’t always available, to machine all the features. This whole car was built in a student shop, so machines had to be shared with other students.
Here’s a closeup of one of the lug joints holding the chassis together. We also ended up using the forward engine mounts to help tie the chassis together. While the tube for the engine mount is 0.035” wall, the mount itself is solid steel. Welding this together was a nightmare. 0.035 wall tube is hard enough to weld without trying to weld it to a nearly solid bar! Sorry, you’re not allowed to see it final welded because it is UGLY.
This is one proud and happy group of guys. Next time we’ll get more into the powertrain, driver controls, and wrapping up some of the other details before competition. If it looks like there’s a lot left to do there is! This was taken at the very end of March and while it looks like a car, there is no plumbing, no intake, no exhaust, and only half a wiring harness. Like the title says, there’s no rest for the studious…