04/25/17 The main (but not the only) scramble right now is to finish the D2TT build, since Pikes Peak is only two months away. We've been waiting for various parts such as exhaust collectors, but today they finally showed up. The first header is now tacked together.
Intercoolers were mounted a couple days ago and the intake collector is in the process of being built (some will notice it's not fully welded yet). The intercoolers are supported off the engine by fairly simple fabricated angle brackets that bolt to the heads. Seems pretty solid.
The collectors are double-slip. A lot more progress will come on this in the next couple days. This is what it should look like when all done.
The CAD model doesn't show wastegates or blowoff valves, those will be added shortly. Parts themselves arrived a couple days ago. This is a mass airflow setup so BOVs will recirculate upstream of the turbos instead of venting to atmosphere. This car will get last year's prototype bodywork so at least that part is already done.
We do need to fabricate new wings for it, and that's still a process. We've tried numerous resins, gelcoats, layups and processes. It's getting better but the test parts are still not coming out the way we want. This is exactly why we don't do structural composites - process is everything, and a lot of the time you don't know if the part is good or not without destructive testing. We're just not set up for it. However cosmetic and semi-structural parts like wings are within reach and it's our goal to get good at doing them. Here's an example of a recent part - you can see it has some dry voids along the weave. It starts saturated with resin, so it's not from lack of that. Something in the process draws it out.
But we've nailed down a lot of variables already, this will get resolved too.
I've been posting GTC upright progress here, since they can (and likely will) be D2 upgrades. We're now done with all machining. Aluminum parts are back from anodize, steel parts are at heat treat and will go to plating next. Corvette bearings have been modified for the drive pins.
I may have mentioned that these have been some of the most challenging parts we've done machining-wise. The toughest of them are the stub shafts, which both transmit the torque from CV joints to the hubs and hold the wheels on. Our equipment is pretty compact so we're stretching the limits of its capabilites, and have to be both clever and very careful in the setup.
Each shaft starts as a 47lb billet of alloy steel that is machined down to about 4 lbs in the lathe.
It then goes out for splining which we can't do inhouse. Next come the mill ops. One of the many challenges is holding the parts securely and precisely in several orientations (within 0.001" in XYZ). Below is a screenshot of the tooling jaws I designed for the job. They do a lot, including other parts that go into the upright package.
We are especially constrained in Z travel with the mill. Below is an illustration of the part in the fixture, and the tight clearance that occurs during tool change. It is not coincidental but a result of much optimization. As we say, clearance is clearance.
There are quite a few tricks necessary to keep things from crashing into each other. It's complicated by the fact that we're tapping threads into steel, which is prone to breaking taps and getting them stuck. This actually happened here so I reverted to the strategy of starting the treads in the machine to make sure they're perfectly straight, then finishing them by hand later. Fortunately we were able to save the part.
The horizontal ops are less scary but equally challenging, since the drilled hole needs to be perpendicular to the milled slot.
Machining more mundane parts afterwards is a relief of sorts. Almost vacation-like :) And then it's done.
Some might notice that there are actually three kinds of shafts in the picture - large CV, medium CV and no CV. Subsequent parts we produce will have material sized appropriately and will significantly reduce the machining time, but since the mix actually changed mid-stream on this batch, we started them all as full billets. Yes, we recycle the chips. No, we don't get anything worth mentioning for them, it's more for the environment than any financial incentive.
Like all our upright designs, the GTC has a large degree of modularity and we can accommodate a wide mix of geometries, CV joints and brake packages. The two current GTC customers are very different - one is an LMP style endurance racer powered by new generation Hartley V8, the other is the Envate Hypercar. The endurance guys are using AP Racing brakes:
The Enviate uses an even bigger Stoptech setup with carbon rotors. I'll post some pictures when I have them.
Keep in mind that the same upright will work on the D2 as well, with some suspension arm changes. If you have a build that could use them, let us know (we can do standard Corvette or 5x114.3 bolt pattern if centerlock is not necessary, at significantly reduced cost). And, the parts we've devleoped can be used to make a Corvette centerlock kit - HRE and Jongbloed can make the wheels to work with it.
Site Sponsors and Links:
- CMS Lap Timer - Advanced Track Timer App With Video Integration
Tire Rack - Tires, Wheels (use link when buying wheels/tires to support this site)