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I have an existing C6 steel chassis race car on the other side of the world in New Zealand and I am considering building a better chassis.
Its a well built chassis with a cage the copies all the cars in the Callaway GT3 cars. It was originally built for the Asian Supercar Challenge in 2008. It has all Z06 panels and runs 18x11F and 18x13 with Pirelli slicks 305 & 325. So it doesn't lack rubber. LS7, JRZ 3 ways, all spherical bearings, AP brakes, Sequential transmission etc so generally doesn't lack for to much.
We generally run endurance races of an hour and sprint races but I need to change from running the standard tanks and end up with fuel cells to get nearer 32 gallons total but the cage gets in the way and doesn't really allow modification to achieve what we need. Ideally also the car could be lighter. Its currently 2900lbs with next to no fuel. I race against another C6 that is more like 2650 pounds. My car still retains the full windscreen surrounds, door pillars, roof halo etc. We run to a set of safety rules ie cage, seats, harnesses etc but car build is basically open book.
My question then is if you could do a build with no rules or restrictions on design what would be worth looking at. I had been considering things like: Lifting the subframes up into the rails, exhaust out passenger side, maybe shifting the engine back and shortening the torque tube. We have access to GT3 panels so we can look to run the car lower than we can in terms of tire clearance available with the Z06 panels in comparison.
Also I have access to a C5 donor frame. Assuming that we would keep little of the chassis apart from the main rails I am guessing there is no great disadvantage with using the C5 frame?
Here's a photo of the chassis of the guys I know well and race against. In this case they have adopted the approach of removing as much of the car as possible in the search of weight reduction. For instance the lightweight doors they made hang directly off the cage. The tunnel and rear bulkhead structure in front of the tanks has gone so much more reliance on the cage now maintaining the structure of the car.
One of the well respected builders in the US - Doug Rippie Motorsports -has an offering similar to what you want to build. Here is a link to the RTR - ready to race car that they build. Very nice - very fast using mostly factory components. Maybe you can get an idea or two from them.
If you are looking for the better mousetrap, I think this is it. I haven't heard anything about these in a while but in concept, this is about the best of all worlds- a tube frame, lightweight race car that uses stock factory parts: http://aviracing.com/gt1-corvette/
Basically, the car just needs to reduce weight. Building up from the bare chassis does that. Gutting an OEM car is more difficult.
A GT1 car can be build using a stock car road race chassis with a 102" wheelbase. But if the race car is built on a Corvette chassis instead, that gets an independent rear suspension and the engine block positioned behind the front axle line.
Basically, to build race cars we just need an affordable supply of Corvette C5 chassis. A stock car chassis is only about $6000 so the C5 Corvette clone chassis with rollcage needs to come in at no more than $12,000.
The reason to emphasis the C5 chassis is that it will be out of patent protection in January of 2017 if not before
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Thanks for the replies. I have read about the DRM RTR and the ATI. Both nice builds. In guys who in fact own the chassis pictured have dealt with DRM for quite a few years.
When I said no rules I should have been slightly more specific in that the series currently saids no tube frames. So I need to start with a frame but after that point there is no rules. If I removed about 80% of it I might be pushing my luck though.
It would be interesting to know how much chassis could be removed and with strategic replacement of tubing create more torsional rigidity. I have an article from 2005 when the C6R was built of the GM racing manager said at the time "Being a ladder frame, basically like a truck with the hydroform frame rails and some cross embers, it is very tough to get the torsional stiffness" The likes of the C5R chassis which I have attached pics of removed alot of material from the main chassis rails for the exhaust but by boxing it back in the strength is likely maintained.
The C5R certainly has some interesting sheetmetal additions and chassis alterations. The photos are of the chassis being rebuilt in more recent times. Would be interesting to understand some of their ideas in terms of suspension and cage/chassis design.
Main frame rails with roll cage produces a car that weighs 2900 pounds ?
That's a puzzle but come to think of it, it's the short wheelbase C3 that comes in at about 2500 pounds.
I would get rid of OEM chassis pieces but I wouldn't reduce the strength of the frame rails even with roll cage build out. (The C6 frame rails have a wall thickness of 2mm.)
The C6 Z06 has aluminum frame rails. Of course the sanctioning bodies usually don't alloy aluminum roll cages. (But 7003 aluminum does weld better than 6061 and that's something to keep in mind.)
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Assuming that you have to start with the stock frame rails and you can't make a tube frame from the get-go it would be helpful to lighten the stock rails.. a lot... Time to make a trip to the acid vats and "chemically mill" some weight from the frame.
As you've noted, the frame rails provided much of the stiffness that was required in the stock car. Once you go "three dimensional" and make the cage the frame the rails don't need to be nearly as heavy to do what they need to do.
Also note in the C5R chassis how the front suspension upper mounts were stiffened laterally by the two cage elements going forward from the firewall on each side and how they were triangulated after the firewall. This is a huge element in stiffening the chassis in torsion and you need to make sure you implement this type of feature if you want to get rid of the tunnel. Once you do that the old frame can be extensively lightened and you won't notice it.
Also note that the "tunnel" is still in the C5R... They kept it, for whatever reason (and it could have been rule related) and it still add stiffness to the system. If you're going to get rid of the tunnel at least put in a metal floor. You need to make sure the bottom of the cage is "boxed". Without it you don't have a very stiff system.
Just remember, as "Big Daddy" Don Gartlits used to say... "It gets hard to add in any more lightness".....
Fwiw, you can get a legit endurance steel chassis C6 to 2600lbs, cool suit and all. You can remove some items not necessary, and achieve 2525-2550. This is no expense spared, however, and full bumpers and frame intact. Nothing removed, only added.
Back in the day, user "BPC5" had his autocross c5 down in the 2350lb range. This was no second fuel tank, wet sump, small wheels and brakes, and minimal minimal cage.
Fwiw, you can get a legit endurance steel chassis C6 to 2600lbs, cool suit and all. You can remove some items not necessary, and achieve 2525-2550. This is no expense spared, however, and full bumpers and frame intact. Nothing removed, only added.
Back in the day, user "BPC5" had his autocross c5 down in the 2350lb range. This was no second fuel tank, wet sump, small wheels and brakes, and minimal minimal cage.
Thanks Lou, how did the GrandAm cars compare in weight without the OEM chassis rails?
In hindsight I would have done a DRM-RTR instead of working backwards from my street car. DRM gutted and caged my '07 Z06. With cage and OEM glass(windshield, rear hatch) the car is roughly 3000lbs with half a tank of gas.
It would be really tough(expensive) to lose another 200lbs and get under 2800lbs.
I saw their RTR build from beginning to end. Amazing build. No compromise.
01-17-2016, 04:07 AM
C6 Road Race - No Rules Build
