Aluminium AC Cobra Chassis

WKB · #1 (**permalink**) 06-04-2009, 06:11 AM

Came across these photos which looks like an aluminium chassis for an AC Cobra

Warren

stephen low · #2 (**permalink**) 06-04-2009, 06:01 PM

Hmmm.....that would be nice............and light!!!

sambo · #3 (**permalink**) 06-04-2009, 07:07 PM

And brittle with age?

albanycobra · #4 (**permalink**) 06-04-2009, 07:23 PM

Wow that looks good.....

Aussie Mike · #5 (**permalink**) 06-04-2009, 07:29 PM

Looks like he's welding it with a MIG. I reckon there must be a lot more to it to stiffen up the front end. It'll be interesting to see how it develops.

Looks like it's right hand drive. Is it someone in Aus? There's a Falcon ute in the street.

Cheers

cdnus · #6 (**permalink**) 06-04-2009, 08:20 PM

Looks like they are real serious about it, there is another sitting on the trailer in front of the one being welded.
Just like Kirkham---you can't build just one.

Craig

400TT · #7 (**permalink**) 06-05-2009, 06:48 AM

Quote:

Originally Posted by sambo

And brittle with age?

Your kidding right? If they know what they are doing, they won't have any problems. It's all about using the right design, right materials and right manufacturing/production techniques.

Not a Cobra chassis, but I'm happy to share the aluminium love.

albanycobra · #8 (**permalink**) 06-05-2009, 06:45 PM

I guess if / when one of these alloy chassis cars gets registered and does a few years on our rough roads we will all know if they will do the job.

sambo · #9 (**permalink**) 06-05-2009, 08:52 PM

Quote:

Originally Posted by 400TT

Your kidding right?

Craig, we're not all coach builders!

400TT · #10 (**permalink**) 06-06-2009, 01:22 AM

Fatigue testing is a good idea.

Then for good measure produce an incredibly stiff chassis. The chassis I posted above(without roll cage) is many multiples stiffer than registration requirements, even here in QLD.

Jac Mac · #11 (**permalink**) 06-06-2009, 05:50 AM

Quote:

Originally Posted by 400TT

Fatigue testing is a good idea.

Then for good measure produce an incredibly stiff chassis. The chassis I posted above(without roll cage) is many multiples stiffer than registration requirements, even here in QLD.

Not that any kit car is probably a good thing to have a major prang in, but I often look at chassis like this and try to visualise which way the panels would deflect in a serious head-on type road prang, the Cobra chassis in the first post has inner guards that could fold back like a guillotine if hit in the right spot, although it appears that the front X-member is going to be bolted in at multiple points. The GT40 chassis I would hope might deflect up & back into the dash area to act as an energy absorbing area rather than retaining its shape & giving the occupants a serious jolt. Might have some sore toes afterwards though.

albanycobra · #12 (**permalink**) 06-07-2009, 12:18 AM

Craig what is the torsional stiffness? we all know DRB and RF....

400TT · #13 (**permalink**) 06-07-2009, 02:29 AM

Jac Mac, safety is really important to me. We do have those bolt-on aluminium chassis extensions on the front of that chassis as well that should absorb some of the impact energy before it gets to the 1/4" aluminium plate used in that front tub section. You've also got to consider the strength on the welds as well. I certainly feel that the RCR designs are as safe as they can be given the restrictons. We've had a few RCR's involved in significant accidents now and all held up very well, kept the occupants safe and were easily repaired.

We all love our Cobra's, but you've also got to consider what is going to happen to that engine and transmission in a major frontal impact.

Albanycobra, I'm guessing you are chasing the RCR GT40 figures. The torsional stiffness is academic in an RCR GT40 as it is multiples more than what is required for registration or for performance reasons. They are stiff as a result of being built for longevity and strength. "Built like a tank" is a common phrase I hear from Fran Hall of RCR USA.

Due to other manufacturers using the NM/deg/M instead of NM/deg etc to significantly pump up their figures, we have decided to simply not publish them. I personally don't believe any figures I'm told unless I can view the chassis report. Past experience tells me the figures seem to get distorted by word of mouth.

I have copies of many, many chassis test reports at the factory. It makes for some very interesting reading as the higher 6000Nm/deg requirement in QLD really catches some manufacturers out. And that's 6000Nm/deg not 6000Nm/deg/M.

Hope that helps.

Does FFR Coupe make 6000Nm? The integrated full roll cage would really help it.

albanycobra · #14 (**permalink**) 06-07-2009, 05:49 AM

If the RCR is so stiff why not publish test results....it could only sell you more cars? I'm not having a go or trying to start sht just wondering why the secret if it blows the competition away.

I have tested many chassis over the years and have a bit of an interest in Torsion testing, I am also interested in the CAV chassis. I built a test rig years ago that is still being used today to confirm torsional figures for Locosts / Cobra's and one off jobs. These days it uses a load cell instead of weights.

[/IMG]

The only way to measure Torsion is through the wheels.

FFR will not publish Torsion test figures, beats me......

DRB seems to be the only Manufacture that lays it all on the table for everyone to read and I applaud Peter Ransom for it......

stephen low · #15 (**permalink**) 06-08-2009, 03:11 AM

Dave

A curiosity question from one that know's little on the science but isn't the suspension operation a variable you can't factor for, hence why a chassis's twist is measured?

Can understand the leverage starting at the wheels but you have a moveable linkage to the chassis to allow for, so can you really measure at the hubs with fixed suspension and replicate actual twist reality?

I'm keen for a little enlightenment.

Cheers

Aussie Mike · #16 (**permalink**) 06-08-2009, 03:21 AM

I think it makes sense to do it that way. All the twisting loads the car will experience on the road are transmitted through the suspension.

Nice jig setup Dave. Well designed and though out.

Cheers

LoBelly · #17 (**permalink**) 06-09-2009, 09:06 AM

I think that plate aluminium is an excellent choice for a chassis.

I helped my brother put together an ally boat - very light and strong - and a great material to work with (pity I can't weld really

)

Having used (or helped with) this material I am not surprised to find it being used for Cobra Kits - the chassis will look a little different but I anticipate they'll turn out very rigid and light.

LoBelly

Hoofa · #18 (**permalink**) 06-09-2009, 09:24 AM

Albanycobra,

That's a pretty cool test rig. Here is mine, I invested $4 into it for the lag bolts to fasten it to the floor. Everything else was kicking around the shop. It's not on the lift, it is sitting on angle iron placed under the shock mounts. Bouncing the weights was a great tool to see where the chassis was flexing.

Jac Mac · #19 (**permalink**) 06-09-2009, 02:06 PM

Quote:

Originally Posted by albanycobra

If the RCR is so stiff why not publish test results....it could only sell you more cars? I'm not having a go or trying to start sht just wondering why the secret if it blows the competition away.

I have tested many chassis over the years and have a bit of an interest in Torsion testing, I am also interested in the CAV chassis. I built a test rig years ago that is still being used today to confirm torsional figures for Locosts / Cobra's and one off jobs. These days it uses a load cell instead of weights.

[/IMG]

The only way to measure Torsion is through the wheels.

FFR will not publish Torsion test figures, beats me......

DRB seems to be the only Manufacture that lays it all on the table for everyone to read and I applaud Peter Ransom for it......

Dave,
CAV claim 32000 NM/deg and have put out a report on that. I would point out that the test rig was bolted virtually flat plate style to front & rear of tub/mono & did not link thru suspension pickups as yours does so results are particular to their test rig, Just as yours are to your rig.

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..

This is why most of these discussions go nowhere as data to be relevant needs to be collected from the same type test rig.

stephen low · #20 (**permalink**) 06-09-2009, 04:38 PM

So the real question is that with all these specified torsional test parameters is there a standard rig specified?

I work in an industry with NATA test result requirements, ie standard specified testing parameters, which means that within fine limits, tests should be reproducable by any lab, is there the same standard of expectation for torsional twist testing?

Sounds like there is not or am I wrong?