Chassis Rigidity

I was curious if any one knew the flexibility of some of the other GT40 chassis out there?

GT40 Australia claims their's at 7,000 nm per degree

New Zealand LTD says their's at over 17,000 nm

And, RF has their's at over 20,000

Curious what some of the competition is at. Tornado? GTD? ERA? Etc.?

Doug

 

[Robert Logan]

Doug,

When we did our torsional rigidity tests which we conducted on a bare chassis (no aluminium panels etc) we were outside the tabulated results which stopped at 12000Nm/deg. We extrapulated the results and got the figure you stated above but I only claim the 12000Nm/deg as I am sure that it exceeded this and only 6000Nm/deg is required for a V8 engined car manufactured in Australia.
We were also required to do beam tests which we again "easily" passed (my engineers words).

The main reason that I chose to perform the tests on the bare chassis was that I did not want to be restricted to following a strict aluminium skinning reigem to comply with the test vehicle. I can now skin our cars with almost anything as long as it keeps out the rain. More to the point I can reduce weight with very thin coverings if I so desire and I do.

Best wishes,

Robert

 

[Guest]

Quoting Greg C's reply to this post http://www.gt40s.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=000213

RF - 14,751 lbf*ft/degree
ERA - 7,375 lbf*ft/degree
DBR - 5,347 lbf*ft/degree

And quoting from the RF web page
"The chassis has undergone torsional rigidity tests and has had, in excess of 20,000 Nm of force applied, the result was only one degree of deflection" "In this form the chassis would have an integrated roll-over bar"

So the RF car was tested with an added roll bar. I'm assuming that the chassis is usually sold without the roll bar. It would be nice to know the torsional rigidity figures for the RF chassis in the configuration that it and other manufactures are usually delivered, without an added roll bar. Otherwise it's not a fair comparison. Also then any "extrapolation" would not be necessary.

 

[Mark Worthington]

I ran across this quote from Roy Smart in the epic thread, NEW CAV MONOCOQUE VS OLDER ERA?:

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>I have built two GTD spaceframes thus far and the stiffness of the chassis is quoted at 2700lbs per degree deflection. The aluminium monocoque I'm building has been quoted at 3400lbs per degree deflection and it is expected that once the space between the fuel tanks and the side pods is foam filled, this figure will increase by 10 to 20%.<HR></BLOCKQUOTE>

The figures Ray quoted are not dimensionally correct but I assume he was referring to lb-ft per degree. Otherwise, one would need to know the length of the moment at which the flexing force was applied to make a fair comparison. If the units are indeed lb-ft per degree, the GTD torsional rigidity value seems low in comparison to its contemporaries. Any comments from the GTD people?

Regards,
Mark

 

[Ian K]

Kalun,

Greg's post linked 2 seperate sentences.
The measurement was made with a bare chassis.
The Robert goes on to say that the chassis
can be further refined for track use,
and this would include an integrated rollbar.

At least that's how I read the statement
on RF's site. Here's the full quote:

Chassis
The basis of the Roaring Forty is a fully triangulated space frame with all mounting and fixings already MIG welded on precision jigs. The chassis has undergone torsional rigidity tests and has had, in excess of 20,000 Nm of force applied, the result was only one degree of deflection. Our intention is that it can be used as the bases of an inexpensive but high-performance road car, while at the same time capable of being refined and modified for more serious use, even competition. In this form the chassis would have an integrated roll-over bar, four-point seat harness mounts and full rose jointed suspension.

Ian

 

[Robert Logan]

Kalun,

The roll bar that I was refering to is the one that is fitted to ALL cars and is clearly seen in many photographs on our web pages.

ADDITIONAL to this we offer TWO cages, a half cage which consists of a rear tube with a cross brace and two rear braces. The second is basically an extension of the half cage and has a loop around the front screen and twin central roof braces and also two side vertical braces. Both cages are made in Chrome Molly tubing and are bolted on to plates that are welded to ALL chassis made at Roaring Forties.

All torsional tests were conducted on standard ROAD chassis. I hope to conduct torsional tests on a fully caged race chassis one day but this would only be for my interest and is a very expensive exercise.

I hope this removes any misconceptions.

Best wishes,

Robert

 

[Bob Putnam]

Kalun failed to scroll down to my correction in the previous thread. I'll forgive him this time.

Me: "Greg's right and "My bad"... Just goes to show you that my memory isn't what it used to be - and it wasn't too good to begin with.

12,500 lbft/deg=17,000Nm/deg

The ERA should be the same."

 

[Guest]

As a GTD owner, I am not in a position to answer the detail on Roy Smart's quote above. I am not knowledgeable enough in that area, although I understand the basic principle, the actual engineering in this is over my head. If I remember when I next talk to Roy I shall ask him to look at this thread for his thoughts.
Malcolm