Greetings Locost Forum Members,
Long-time lurker, first-time poster here. Hopefully my build will interest some. Comments are welcome.
This is the build log for my current project, a hot-rod inspired exo car based on a C5 corvette 'roller skate'. Often called a rolling chassis by those who sell such things, the roller skate came with the full drivetrain, suspension, wheels, brakes, fuel system, computers and wiring, steering column, pedals and hydraulics, and lots of other stuff from a 2000 M6 Corvette. 55k on the clock. Not as cheap as a Miata roller skate, but I like a V8.
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Hopefully my reason for calling it 'hot-rod inspired' will be obvious from the photos. The tube chassis was to incorporate a full cage, and I knew it had the potential to look entirely un-aesthetic. So I drew before building it and found a basic shape I liked. The high cowl is not great for visibility, and I don't need it for the engine, but it looks so much better than anything else I could draw. I used graph paper and drew it to scale to sort out the aesthetics, and built from the drawing. The steel is not a perfect replication of the drawing, but it's close to within a half an inch or so.
The engine is an LS1, which makes 350ish hp/tq when it's in the Corvette, in this car it will make about 400 initially, with different exhaust and intake, and maybe I'll bump it up to 500 or so with heads and a cam someday if that seems like the thing to do. No forced induction is planned.
The Transmission is a T56, and the diff is Getrag. Drivetrain should be good for 500 crank horsepower without any changes. Might need a stronger clutch at that level though.
The suspension is all aluminum, including the subframes, and I may or may not use the transverse springs initially, but the finished version (such a thing?) will employ coilovers.
I intend to use stock brake parts except for the pedal assembly and master cylinders. Same for the clutch. I've not yet picked out a pedal assembly, trying to decide between Wilwood and Tilton.
I have two sets of C5 thin spoke wheels, so although they are staggered from the factory (17x 8.5 front, 18x9.5 rear), I'll be able to run the car square. They are light for stock wheels, forged. Also cheap.
I'm using a pair of Kirkey seats. Comfortable, even with no padding, and 12lbs each.
If and when I run an actual windshield, it will be split down the middle and Lexan. Duval style.
I'll run a 5 gallon plastic vertically oriented fuel cell mounted behind passenger's seat on the other side of the rear firewall, and will have space if not provisions to mount another behind the driver's side. The idea here is to be able to run a very small fuel load without sucking air. No foam. I'm leaving space in the back for a large, road-racing fuel cell, just in case, but I envision this as more of a short race vehicle. An autocross/trackday/occasional street driver.
The space/tube frame is being constructed from locally-sourced mild steel round tubing in various diameters and thicknesses. The really heavy stuff, for just a couple of spots, is 1.75x.134 wall; the lightest stuff I'll probably use is 3/4 diameter in 16 gauge. It's all ERW except for a few pieces of DOM I had lying around. Most of the tubing is 1.75" diameter with .120 wall. I would have preferred to use .095, but the 11 gauge is the only wall thickness available at my local supplier in that tubing diameter (it's only $1.50 a foot), plus it bends and welds very nicely. The smaller diameters of tubing have thinner walls: 1.5" x .104"; 1.25" x .078"; 1" x .065". All the welding is FCAW.
My weight target is under 1800 lbs wet in race trim. Should still be under 2000 in street trim. This goal is based on my calculation of the weight of the roller skate at about 1200 lbs. With a 400 pound allowance for my steel tubing, aluminum bulkheads, and bracketry, I'll have 200 pounds left to 'spend' on battery, fuel system and load, cooling system, seats, controls, wiring, gauges, and hardware. This is a heavy car by locost standards. It could be 200 lbs lighter if I valued things differently, but I decided at the beginning of this build that chassis stiffness/robustness, safety, and an overall shape I find aesthetically pleasing were to be more highly valued than minimal weight.
I'm shooting for a 50/50 weight distribution front to back. It should be possible, barely, with me in the car. I'd love to have a rearward weight bias of 5%, but with this drivetrain layout and wheelbase I don't think that's possible without ballast.
I do not plan to have a driveshaft tunnel, as there is a torque tube. I want to take advantage.
The full chassis will unbolt from the subframes--8 bolts--and lift off. So the engine will come out the bottom. I plan to take advantage of that, structurally. That advantage will be offset by the structural disadvantage of not having a continuous, flat floor. I'm still working on solutions there.
Finally, I know it's asking for trouble, but I plan to put the radiator in the back of the car. It's really the only complicated aspect of my plans. I have two reasons for this: first, I'd like more weight in the back of the car; second, I might be able to turn it into an aero advantage on this highly aero-disadvantaged vehicle. It will add weight and complexity, but I think I have a little wiggle room on this car when it comes to cooling. The openness of the front of the car, the position of the engine, and the aluminum block are big advantages in keeping temperatures down. If I can use aluminum tubing under the car to plumb the coolant to the back (fins?), I'll gain some extra cooling, allowing for a smaller radiator, and perhaps negating some of the weight penalty of the extra plumbing and coolant. It shouldn't be a problem getting air to the radiator in the back; hopefully I can scoop some from underneath. This is an exo car, after all.
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