Starting my GTR chassis build

#1
Hello to everyone here. I'm laying out my chassis for my scratch build Mercedes CLK-GTR Tribute street car and need advice on tube sizes as I want it to be strong but not too over built. I plan on using round tube for what will make up the 2 main roll bar hoops at the windshield A-pillar and B-pillars and their overhead connectors. Note: the doors will hinge forward off the A-pillars. I am considering 1.5'' or 2'' round tube in 11 or 13 gage. The remainder of the chassis will consist of square tubing 1.5'' x .060 (40x40x1.5mm) with secondary supports from 1''x1'' x .060 (16ga) 26x26x1.5mm.
The cars specs:
Audi 2.7ltr V6 bi-turbo 240HP
Boxster 012 5 speed
Corvette c5 susp & brakes all around
100'' / 2.55cm wheelbase
Target weight 2300lb/1043kg
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Any advise on choice of tubing is greatly appreciated, If I may have left out something critical needed just ask. I look forward hearing back from fellow members and starting to build this dream car of mine. All the best, Vinny

Below are a drawing and photo of the actual race car. I'm not building a monocouque as the original, instead I will clad the lower half of the tube framed cabin with aluminum skin.
 

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#2
Any advise on choice of tubing is greatly appreciated, If I may have left out something critical needed just ask. I look forward hearing back from fellow members and starting to build this dream car of mine. All the best, Vinny
 

John

Active Member
#3
Vinny, 40x40 x 1.6 will be fine for the main chassis rails, that's all ive used on numerous GT40 chassis ive done and my McLaren with 25 x 25 x1.6 diagonals.

Now your roll hoops, I think you will find if you intend to take it near a track you want the cage to be FIA compatible which will mean main hoops of 44 x 2.5 wall CDS [cold drawn seamless tube] of 350MPA min requirement,
the diagonals can be 38 x 2.5 CDS also 350MPA min,
remember its your neck so do it once and do it right, and you'll have no problems down the track
look forward to seeing it all come together
cheers John
 
#5
Vinny

I am building a McLaren M8B as a road car and have gone a little stronger than John and my previous track car and used 40mm x40m x2mm, now that may be overkill but side impact is exceptionally strong with the only week point being going under the vehical in front.
All my bracing is 25mm sq x 1.6mm tube and some areas like dash surrounds is 19mm sq x 1.6mm.
My set up will be a lexus 1uz 4ltr V8 running thru what i hope will be an Audi transaxel with around 280hp.
I plan on the car being under 1000kg as the stronger chassis would only add around 30 to 40 kg n weight.
Like John, happy to help with any questions on scratch build stuff.
Cheers
Russell
My brother has purchased a tranaxel in the states and currently its sitting in the boot of his new Plymouth Wildcat some where between USA and NZ so i am nervously waiting to see what he got me....should see it in a couple of weeks
 
#9
John, Thank you for posting the sizes on the tubing, I've written it in my notebook and will be calling the local steel supplier to see what he has to offer up, and they should have the equipment to bend my roll hoops too.
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Russell, I was glad to read you and John were using similar size tubing, I had begun drawing my frame in 1.5'' square tube and now feel confident to stay with that size. I work a few evenings per week as a graphic artist as it keeps my creative side active and has led me to learn Google SketchUp to draw in 3D.
I hope your brother has something Stuttgart flavored for you, not too many FWD Audi's here in the states. When I picked up my Boxster trans (2002 EFD from a 2.7 car)I was surprised to see cost-cutting parts like using a plastic sleeve on the throwout bearing, and a plastic Slave cylinder. But those are easily upgraded.
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I greatly admire the skill of everyone here, and I aspire to make this car better than my last one. Thanks for taking the time to reply.
Cheers,
Vinny
 
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#10
When I opened my email this morning I discovered I had won an auction for a Corvette C5 rear suspension assembly. It's complete rotor to rotor minus the diff. It's a 2 hour drive to pick it up which will likely happen next week. It's a good day. Cheers Vinny
 
#11
When I opened my email this morning I discovered I had won an auction for a Corvette C5 rear suspension assembly. It's complete rotor to rotor minus the diff. It's a 2 hour drive to pick it up which will likely happen next week. It's a good day. Cheers Vinny
Another bit of good news, also got an ebay note this afternoon saying I was the winning bid for a complete front suspension and rack pulled from an 87 Corvette. Should be a busy upcoming week. Cheers Vinny
 
#13
Hello Graeme, that's a terrific link you posted. It will be very helpful. Thank you.
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Both suspension assemblies are here now. They are 1987 C4 front and 2001 C5 rear (Corvette).
 
#15
I've managed to get up the courage to post my chassis in progress pictures. As this evolves I hope to improve it with each new version. Please consider giving advice on tube placement and all areas that need additional reinforcement so far. I value everyone's vast knowledge on this forum and look forward to reading all replies.
- The colors indicate:
Blue Square tube = 1.5'' / 38mm
Green round tube = 1.75'' / 44mm
yellow square tube = 1.0'' / 25mm
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Thank you very much,
Cheers! Vinny
 

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John

Active Member
#16
Hi Vinny whats your E mail address and ill send you a couple of chassis pic to give you a guide to work from.

cheers John
 
#18
I was able to spend a couple of hours in the garage today, so I broke down the Corvette rear suspension into left and right assemblies on rolling dollys to make them easier to move around. Thanks to John for jumping on with advice on chassis design, its a great help to have guidance from more experienced builders. I'm working on establishing the rear track width using the outer corvette CV and shaft, and looking at Porsche 930 inner cv's. The Porsche cv's have the correct 28 inner splines to match the Corvette shaft. I will then need a pair of larger 108mm- 6 bolt Audi-VW axle flanges to replace the Boxster transmission's 100mm parts. My other option if the Porsche cv's won't work is custom axles.
Cheers
Vinny
 

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#19
Ordered the Porsche 930 inner cv's today. I took apart the corvette axle beforehand to confirm that the splines on the shaft were indeed 28 count. still trying to locate a pair of VW axle flanges to match the 930 cv's. -Vinny
 
#20
Terry, just came across your post in Udo's MB6 build thread. I'm going down a similar path with the 930 cv's and was glad to hear you're having success running without c-clips on your axles. This is great news and will give me additional options. Thanks for sharing your experience. Cheers , Vinny
 
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