Aluminium AC Cobra Chassis

[albanycobra]

I would question your test rig in that the pivot point is below the chassis at front and therefore as you apply load that you are not going to get a true torsion only result. If you were to break down the chassis to simple form the lower plane of the chassis is simply being twisted as its at close to the pivot height, but the upper plane of the chassis is being subjected to a parallelogram type load. If you were to raise the front pivot point you might find you get even higher test results than your current readings as many chassis simply have heavier material in the lower frame rails which would now be subjected to the parallelogrm effect as well..

JACMAC you need to read the NCOP12.LT (National code of pratice) test procedures.. There you will find that the machine in question is set up and tests the chassis exactly as per Government guidelines. Yes they have pictures.

http://www.infrastructure.gov.au/roa...s_3Feb2006.pdf

Maybe the machine does not make sense but that is how they want the chassis tested. My guess is they started like that and now keep it the same so apples can be compared with apples.

[stephen low]

Thanks Dave that answered my question.

But the beetle pics made me remember that I have an engineer's report somewhere in the files with that same picture in it.

I'll go and dig it up to see what torsion rating the GForce achieved at test originally.

Cheers

[Aussie Mike]

Dave,

Did you test your Daytona chassis on that rig? How did it perform? Maybe F5 might like to buy the official report off you so others could use it.

The CR is supposed to do better than 11,000 Nm/degree acording to the engineers report that came with the chassis.

Cheers

[albanycobra]

Mike it's not up to me to disclose FFR's torsional figures as there is
another company importing and distributing them, it wouldn't be right.

IMHO a huge torsional figure does not make a car any better than an average figure car to drive. I bet someone like Craig Lowndes could tell the difference
bewteen a 7000nm and a 11000 but the rest of us couldn't.

[Aussie Mike]

I don't reckon it makes that much difference either. A degree or so difference in twist it's going to mean anything on the road when you take into account the amount of movement in the suspension.

You might notice pick the difference in the body movement Depending on how it's mounted but I doubt it.

I think a flexier car with a well designed suspension setup is going to feel way better on the road than a rigid chassis with less than ideal suspension.

Cheers

[albanycobra]

I agree 100%......I think sometimes torsion figures are used as phallic symbols.

IMHO a chassis's torsional number would make no difference in which brand of kit I bought.

I corner weighted 4 different brand kit cars on the weekend ,2 Cobra's, one coupe, one DRB GT40. I found that even though the torsional stiffness of each car was greatly different, all the cars responded very well to spring platform adjustments...meaning that all the chassis's where stiff enough that small changes in ride height moved weight around the vehicles. A sloppy chassis would take inches of adjustment where the DRB GT40 for example showed weight changes/transfer with 5mm of adjustment.

IMHO that means that chassis is torsionally stiff enough for the application of Fun sports car/ hobby race car.
It responds well to changes and really why would it need to be stiffer?

[Tony Ripepi]

Hi Guys,

I seem to remember that Herb Adams built and sold an aluminum monocoque chassis. His was a Cobra kit and it was called the VSE.

Here is a link to an old thread here on Club Cobra that has chassis information and references, including some from Tom Kirkham.

http://www.clubcobra.com/forums/scratch-builders-forum/93643-recommended-reading-chassis-design.html#post913844


Anybody else remember the Herb Adams VSE Cobra, he was in Carmel ??????

Here is a link to the old VSE home page......this monocoque chassis was done in Steel not Aluminum but, the torsional stiffness and the overall design will give some insight to how to do it.

http://www.vsecobra.com/

They are out of business now, I saw the building for sale a few years ago, living quarters on the top floor and huge garage/work shop below.

Tony R.

[Rotty]

As a newbie, and definitely not an engineer, what are the pros and cons of the aluminium monocoque chassis in these photos as compared to a traditional tubular steel chassis?

[Hemo84]

G’day all, new to this forum and looking for some help.
Did anyone find out who was building the Alloy chassis in these pics? I would like to get in contact with them as im wanting to get one built.

Thanks in advance
Dan.

[400TT]

Dan, that chassis is manufactured by BDM (ByDesign Motorsports). Gary Hall runs the show and is a great guy.

We also manufacture aluminium chassis units for our kits, but take a totally different approach to BDM on our Cobra replica chassis.

So plenty of variety on offer.

[dhs.buckley]

Very interesting reading, must admit it made me get my engineers report out.
I can see figures saying around 7220 NM/deg with crush cans behind the front suspension. lots of figures all over the pages and not sure quiet how to read it though.
also it seems to say rhs in the engineers report, but its a tube chassis.
Good thing was, i finally found out the capacity of the fuel tank, its been driving me nuts, not trusting the gauge when it take 38 litres when its empty, but considering its only 45 litres, i must of cut it fine a few times!

[Hemo84]

[quote=400TT;1247810]Dan, that chassis is manufactured by BDM (ByDesign Motorsports). Gary Hall runs the show and is a great guy.

We also manufacture aluminium chassis units for our kits, but take a totally different approach to BDM on our Cobra replica chassis.

Hi Craig thanks for your input, I also have looked at you design, and am very impressed. I also find it refreshing to hear your comments about your opposition as I work in an industry where people aren’t so kind toward one another.
Can anyone tell me if the alloy bodies are available in Australia? Im not a huge fan of fiberglass as I work with aluminium for a living.

Cheers Dan.

[Hemo84]

Are BDM still in business? I cant seem to find any info on them.

[Aussie Mike]

Pace are also the Aussie agents for Kirkham who make an aluminium body cobra. A nice piece of kit if your budget will stretch that far.

Cheers

[400TT]

Yes, we have aluminium bodies from Kirkham. And also Carbon bodies. Be worth checking out both in the flesh to see which option suits you best.

Well this was the web site address for ByDesign. Doesn't seem to be working now, but that may be a temporary hitch:

www.bydesignmotorsports.com.au

ByDesign were at Macleans Bridge a few weeks ago with a trade stand.

It's such a tough industry and with the economy the way it is, it has never made sense for manufacturers to work together where possible and least of all now. Plus I am a huge advocate of researching all kit offerings and selecting what suits the buyer best.

[Hemo84]

Thanks for the help guys. I really would like to build the entire car from scratch but i don't think the resources are available to make it happen (ie drawings, jigs, templates).

I did find drawings to the 427 chassis online for $200 but am unsure if they are any good? My idea was to buy them and re draw it on AutoCad, then design my alloy chassis around that. for $200 its not much of a loss if they are no good. has anyone on here used them?

The Kirkham body looks fantastic and the workmanship looks second to none. Craig would you sell one of these body's just by its self?

I might start a new thread on here listing what I'm looking at doing.

Cheers Dan.

[400TT]

Yes, you can purchase an aluminium body by itself.

Those drawings are not accurate or complete, but a good starter if you want an original style chassis.

Just make sure you are aware of the total cost of compliance when doing a scratch build. But if you have the time, skills and resources would love to be kept update with it.

[Hemo84]

Cheers Craig,
I will deferentially be in contact with you.

I had a feeling the drawings would not be complete. We had been talking about building an alloy chassis similar to the BDM well before i had seen the pics on here. I own a custom aluminium boat building shop and deal with compliance and engineers every other day. we also have our own CNC router so making parts in house wont be an issue. its more of a case of getting it 110% right the first time. so buying an alloy chassis may very well be the best option, just not as rewarding when its all done.

[Thor maine]

I think Herb Adams at VSE did something like this with Corvette suspension and it was super in the handling dept at all the Run n Guns. What ever happened to VSE?

[Ozgur_Tan]

VSE Cobra

Originally Posted by Thor maine

I think Herb Adams at VSE did something like this with Corvette suspension and it was super in the handling dept at all the Run n Guns. What ever happened to VSE?