CAV GT Auto Futura Newsletter

[Auto Futura-CAV Factory]

Please see the attached PDF File.
Tortional stiffness report available: CAV GT | Resurrecting a legend

[Gregg]

Those are some impressive numbers. It didn't think Nascar chassis' were that stiff! I am not an automotive engineer so can someone explain to me how the loadcell is configured and set up to register it's measurements and how that measurement is obtained? Is it a straight number or multiplied/divided by another figure? I see the steel plate welded to the torque arm is bolted to the car in four places. Does that matter? Would the rating change if just the top two bolts were used? The bottom two? Is it even a proper way to measure torsional stiffness as represented?

Thanks for the anticipated education.

I would appreciate a reply from CAV and/or a non competing manufacturer so as not to seem biased one way or the other, however all are free to reply.

[Keith Hardy]

If you remember, the membership got quite heated about this subject on here a couple of years back.

There were, as I recall, some very good "shade tree" ways of testing chassis that some owners had done for themselves. Otherwise, it was a case of some (and by no means all) manufacturers simply stating their chassis stiffness results whilst some members perhaps seem to prefer independent analysis which has never been forthcoming as far as I know.

The CAV would certainly appear to be very stiff that's true...

And then of course someone (probably very rightly) said that the flexibility inherent in the original Cobra chassis enabled it to keep all it's wheels on the ground which was why it was so fast!

It was, in truth a very interesting debate...

[Jac Mac]

I see nothing wrong with utilising the '4 bolt' flat plate in this instance as in the 'real' car situation the bolt in top crossmember would complete the circle/box anyway. The secret if there is one is to have light arms/indicators fixed to the chassis at regular intevals along its length so that you can verify where any weak areas are.

Jac Mac

[Gregg]

Keith, I remember the discussion, however I am no smarter today than I was back then.

[Rob]

I too remember the discussion....it was probably the most heated and irrelivant discussion I have witnessed on this forum. Which I might add is a place where I feel this almost never occurs. Input is usually always relevant and polite.

So...at the risk of starting it all over again......

I think the way these measurements were taken has little validity. By mounting the solid plate to the chassis they have eliminated a any twist at the reference point. Last I checked you can't induce twist in plane to a flat piece of steel. In other words, if the four mount bolts are the four corners of a square, the plate eliminates the ability of the square to turn trapezoidal. So, what this caused is a result of only twist of the longitudinal structures with no ability to twist in the local region of the plate. I do not see this as a full chassis assessment.

These are my thoughts...not yours.... Rob

[Canuk40]

Hi Rob,

You're correct in saying that the mounting plate prevents trapezoid in the reference plane, however as Jac Mack mentioned, the transaxle bracket connects the two upper points.

So if the deflection stength of the rear horse shoe hoop with transaxle bracket bolted in place permits the prior test numbers to be acheived, then the numbers are valid. Or if the test was run again with the pivot attached to a transaxle bracket then there'd be no question.

It's also fair to say that if any brand of chassis was tested in the same manner, the torsional strength of that chassis would be valid on that jig. In that comparative I believe the CAV monocoque would still be the strongest.

Maybe somewhere, someday, somebody brings a test rig to Carlyle or wherever, let's strap the cars down and then see who's on top. That would be fun

Cheers