Mclaren m8a tribute

D

Kris

I am starting a scratch build Can-Am Mclaren. It is not going to be a 100% authentic copy, but I would like it as close as is feasible. I have the fab experience and tooling needed for 98% of the build, and a grand image of what the project should be. My plans are a Porsche 930 box, American v8, semi-monocoque design. I am planning sub 2000lbs (originals are around 1400lbs), and as close to 700hp as possible. I am a working chump, I do not have a massive budget. Power production and overall project progress will be dollar limited. This is a "street" build. It will be a fully legal car to drive, not practical, but legal. Arizona has very laid back motor vehicle rules...

I have a few questions:

-What is the ultimate strength of a stock 930 box? What upgrades should I plan for it?
-Your opinion here; stay true with a BBC or go more modern with a LS engine?
-In the last Can-Am cars, Mclaren used .060 aluminum. Any guesses which alloy? I was planning 6061 T6.
-How much of a stressed unit is a chevy v8 capable of being? Should I just plan to not use the engine/transaxle as a stressed member?
 
L

Leon

Hi Kris and welcome to the Forum and the world of scratch building. A huge but hugely satisfying pass time. 1st question, if you can't afoward to build a proper alloy big block go LS for the road, much easier and lighter. 2nd i would be dubious about using a box that was not designed to have the rear suspension hung off it as part of the stressed section. The Chevy block will handle it no problem but you have to remember the Bell housing and diff section of the Trans axle carry most of the cars weight and road use is very different to track use, tracks are generally quite smooth roads can be very bumpy and that will be hard on the car if there is no chassis past the front of the engine.
Just my opinion, I'm sure ther are others on this forum more qualified to give you guidence. Cheers Leon.
 
K

John

Kris, For what its worth I would definitely use an LS engine, and also have the chassis extend at least to flywheel, bell housing, to take suspension mounts etc, you will like your self for it the long term.
cheers Kaspa
 
D

Kris

I received my 930 trans, kennedy adaptor, and clutch set-up this morning. I'm pumped to see it finally. Started my chassis blueprinting this weekend, reverse engineering a mclaren m8 chassis to get the dimensions.

What tires do you guys run? I'm looking for wide 15" rears, thinking a 13-15"
width. Can't find a suitable tire though, other than the Pzero that is $750 each.
 
M

Mesa

ducdodgers said:
I received my 930 trans, kennedy adaptor, and clutch set-up this morning. I'm pumped to see it finally. Started my chassis blueprinting this weekend, reverse engineering a mclaren m8 chassis to get the dimensions.

What tires do you guys run? I'm looking for wide 15" rears, thinking a 13-15"
width. Can't find a suitable tire though, other than the Pzero that is $750 each.
Click to expand...

The only tire that comes in that size besides the uber-expensive Pirelli is.... A Mickey Thompson Sportsman radial. Huge Can-Am type sizes. Not high speed rated but will get you the look you are after.
 
S

Darnel A.

Supporter
Another tire which would work is Nitto NT 555 R which comes in a 325/50/15. As far as speed rating is concerned i would say ditto for Nitto!

Darnel
 
M

Mick Ridley

Hi Kris,

There are a few of us on this site that are building alloy mono rivited and bonded chassis. Leon is building a M20 replica

http://www.gt40s.com/forum/wings-wheels-keels/28393-m20-dreaming.html

http://www.gt40s.com/forum/lola-t70-lounge/22490-lola-t70-scratch-build.html

http://www.gt40s.com/forum/wings-wheels-keels/12585-ford-f3l-david-piper.html

http://www.gt40s.com/forum/gt40-build-logs/36067-gt40-aluminium-mononcoque-chassis.html

We have all used different alloys. Im useing 16swg/1.6 mm 6082 T6, because it is readilly available in this country, it has very similar properties, to 6061 T6, but there is nothing wrong in useing a good 5xxx series alloy, if I did mine again I would probably use a 5xxx series, as it is easyer to work with. The Macleren M20 used L72. The Lotus 78 used NS4, a 5xxx series alloy
Im useing a Rover V8,and a Renault UN103 gearbox. They are both semi stressed members of the chassis. Will they be strong enough ? I hope so.....

We all look forward to seeing pics of your project as it progresses

mick
 
L

Leon

I'm with Rob on the M/Ts a really good range of sizes in 15" rims as he said and I have just mentioned on your other gearbox thread speed rating is 130mph.

As Mick has just mentioned, there are a few guys doing Alloy mono's I'm using 5052 at 1.6mm and 1.2mm as the M20 used 18 and 20 gauge in the old measure's. The issue with going to a T6 alloy can be if you are folding tight 90s or more there is a chance of fractures on the fold point, especially if you are using thicker sheets.

IMHO the best advice is read right through Russell Ketch's M8 build log. He has built a nice car, may a bit too far from original spec for what you are wanting but a good read all the same. Cheers Leon
 
D

Kris

leonmac said:
As Mick has just mentioned, there are a few guys doing Alloy mono's I'm using 5052 at 1.6mm and 1.2mm as the M20 used 18 and 20 gauge in the old measure's. The issue with going to a T6 alloy can be if you are folding tight 90s or more there is a chance of fractures on the fold point, especially if you are using thicker sheets. Cheers Leon
Click to expand...

I've been bending some test samples out of 6061 T6 and do see super fine cracks on the OD of the bends themselves. Is that an indication of the metal not able to withstand that bend? Is that "bad"? Is there any allowed amount of hairline cracking?
 
L

Leon

Yes it is "bad",For me there is no allowable fracture of the alloy that I would use. If you are comitted to use T6 alloys then there are 2 things you could do 1) use a slightly thiner sheet or 2)put a little more radius in the bends. If you were building a space frome and paneling it then no issue with T6. The other option is to use extruded "Angle stock" for the 90+ bends, this does mean more rivets and more weight. I would just use a 5xx grade alloy, JMHO.
Cheers Leon
 
blueovalz

Terry Oxandale

Skinny Man
And...don't scribe the sheet where the bend is. Use a sharpie or something like that. I've seen the Mickey's and they wide, but TALL as well. a few inches too tall to look period correct.

Although not a member of this site, but here is a photo of project an acquaintance of mine is making. Mono construction of an M6GT. He should have lots more somewhere.

http://groups.yahoo.com/group/Mantacars/photos/album/217823261/pic/857677719/view
 
Last edited:
D

Kris

leonmac said:
Yes it is "bad",For me there is no allowable fracture of the alloy that I would use. If you are comitted to use T6 alloys then there are 2 things you could do 1) use a slightly thiner sheet or 2)put a little more radius in the bends. If you were building a space frome and paneling it then no issue with T6. The other option is to use extruded "Angle stock" for the 90+ bends, this does mean more rivets and more weight. I would just use a 5xx grade alloy, JMHO.
Cheers Leon
Click to expand...

Thanks for the fast responses. I am not comitted to using 6061 T6 but I do worry about 5xxx aluminum being too soft. Again, I am not an expert and am simply using the little knowledge I have. I would use 2024 if I could source locally. I am always looking to save weight in my projects, but not having FEA software I'd rather have the car be heavy and still able to withstand road abuse.

Does anyone have a finished home built mono car that has been field tested, if so what alloys were used?
 
J

Jac Mac

For you guys contemplating alloy mono chassis, a small booklet " Standard Aircraft Hardware- ISBN-O-8168-8500-1 " will supply most info you need in regard to rivet use, bending radii, alloy types etc..
 
Z

zollis

From post #12 "" I am not comitted to using 6061 T6 but I do worry about 5xxx aluminum being too soft."

5xxx ali comes from dead soft as soap to pretty hard as. It is the grade and "H" value of the 5xxx series that determines its hardness.

Kris follow Leon's advise from post 10 and get hold of a book as Jac Mac suggests.

The 2024 stuff is for aircraft use, and easy to get a crack starting if you are not very careful .








Z.C.
 
L

Leon

Kris,

I think the main thing with this kind of construction is to remember its not just what it's made of that gives a chassis its strength and is as much about the way its designed/constructed thats just as critical. A very basic example is I made a cardboard model of my tub held together with ducktape and I could stand on it (105kg) and when I twisted it the only give was in the tape itself, What I'm trying to say, is don't get too hung up on how strong the material is, think of the construction/design.

Cheers Leon.
 
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K

John

I agree whole heartedly on that , as I to made a model of the 5000 chassis, but out of balsa wood stringers, and although I didn't stand on it , I couldn't twist it with bare hands,

cheers John
 
M

Mick Ridley

Leon, Hit the nail on the head with his comments....Because you are copying a proven design, as long as you use the same gauge of alloy you will be ok. With an alloy mono chassis, getting the strength isnt the problem, its more to do with getting the required stiffness.All alloy regardless of strength, has the same stiffness

16 gauge alloy is what is generally used in mono chassis construction because of its stiffness, not its strength.

How you join the alloy is also very important. You will need a good adhesive to maintain the chassis stiffness. Rivets will give the initall stiffness, but it is the adhesive that will maintain that stiffness..


.
 
D

Kris

mickky3 said:
Leon, Hit the nail on the head with his comments....Because you are copying a proven design, as long as you use the same gauge of alloy you will be ok. With an alloy mono chassis, getting the strength isnt the problem, its more to do with getting the required stiffness.All alloy regardless of strength, has the same stiffness

16 gauge alloy is what is generally used in mono chassis construction because of its stiffness, not its strength.

How you join the alloy is also very important. You will need a good adhesive to maintain the chassis stiffness. Rivets will give the initall stiffness, but it is the adhesive that will maintain that stiffness..


.
Click to expand...

Fair enough. I am using soild rivets with Hysol epoxy as my adhesive
 
L

Leon

I think you will be on the right track with that Kris, looking forward to seeing it come together.

Cheers Leon .
 
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