Deflection Figures for a GT40 Chassis

[Des]

Ron
From my understanding the DRB was tested with no roll cage or hoops, just bare basic chassis.
RF test was done as far as I know with full cage fitted.
This would go along way towards explaining the difference.
Of course Peter and Robert respectively are the ones to ask.
Des

[norman falkiner]

Des The chassis deflection figures for RF were I believe done on chassis number 1 , long before roll cages were built or offered. The difference is in the design. Regards

[DAZPT]

If you are realy interested in getting good information ask for a copy of the deflection test report from the chassis builder, anything other than this is usless information in my humble opinion

[Kalun D]

"If you are realy interested in getting good information ask for a copy of the deflection test report from the chassis builder, anything other than this is usless information in my humble opinion"

I've been working in auto fabrication for about 30 years. I designed and built my first chassis from scratch in 1988.

Using Autocad and Inventor I designed a GT40 chassis loosely based on a combination of the KVA chassis and a MK V. Then spent about 2 weeks building an 1/8 scale wood model solely for the purpose of improving and refining the torsional rigidity.

I've spent 4 years so far building this chassis from scratch including uprights machined from 7075 billet on a small mill drill (no CNC), and scratch built stainless headers.

The ONLY parts I'm not doing are the axles and the flywheel. Everything else, all the designing, machining, fabricating, cutting, grinding, sanding, welding, riveting, bonding, bending, shaping etc I've done by myself.

I spent about 3 weeks refining my torsional rigidity test method. I've performed about 4 tests now during various stages of construction in order to monitor progress.

On a scale of difficulty of 1 to 10, compared to designing and machining uprights from scratch, I would say performing a torsional rigidity test is about a 1 or 2.

But you know something? After 30 years I just don't have confidence in myself anymore. I don't think this is "good information", in fact I think it's "useless information". I'm going to search out one of these "chassis builders" and find out who's doing their rigidity tests because obviously they are the ONLY people on the planet who are competent to perform this horrifically complex, difficult and costly "rocket science" procedure.

IMHO

[Trevor Booth]

Kalun,
Well said.

Trevor
PS why did you not run your 3D Inventor model thru an FEA program.

[Kalun D]

Trevor,

"why did you not run your 3D Inventor model thru an FEA program?"

I used Autocad primarily. The Inventor version I used was #4 but it was as a beta tester only so I only had it for a couple of months.

I did look at some of the FEA programs, wanting to check the uprights, but they weren't cost effective for my application. I have since purchased Inventor 8 so the as-built plans will be done there. It's really nice for looking at suspension movement and such.

[Trevor Booth]

Kalun
If you had purchased ProE I could have done it for you. I beleive that MSC can work with Inv models and do FEA on a fee for service basis. http://www.mscsoftware.com
They do this in Oz without the need to purchase the software. What an FEA will do is highlight the joint stiffness and quite often adding a gusset here and there can make a worthwhile difference.
For suspension movement, if you have the ability to do a kinetic evaluation, thats when the fun starts.

[Dave Bilyk]

Just came across this, looks like an interesting read.

'Design of a Winston Cup Chassis for Torsional Stiffness'
by Lonny.L.Thompson, Srikanth Raju, E.Harry.Law
Clemson Univ

web page
regards
Dave

[daveg]

Interesting site here,( 2100ft/lb/deg for the Ultima chassis [img]/ubbthreads/images/graemlins/shocked.gif[/img]) http://www.ultimav12.ca/ Go to the chassis section.

[Doc Watson]

I found this........its from the 'racingicons' site and states that the gt40 original mono tub has a deflection figure of........

'12,500 pound-feet per degree'

These guys shouls know they apparantly have restored more original tubs than most....

[Fran Hall RCR]

I wonder how long ago those figures were "proven" good...
Dont know many owners that want to subject their priceless GT40 monocoque chassis to a true torsional test.....just thinking out loud.. [img]/ubbthreads/images/graemlins/wink.gif[/img]

[Ian Anderson]

Fran

What numbers do you come up with on your Chassis?

Ian

[Fran Hall RCR]

Ian.

I got 8300lb/ft/deg as a base unit without any of my bolt on extras..such as billet mounts and braces ,roll cage, rear shear plate which are standard parts on a completed roller/car or the new aluminum inner and outer roof section that we are currently working on.... [img]/ubbthreads/images/graemlins/grin.gif[/img]..so when we rerun the test with all of the options and a full roll cage
I will have my definative results and I will post the official paperwork ..!!!

[Ian Anderson]

Fran

From what I have seen elsewhere that is a great figure!

As you say with the extra bits WOW

Thanks
Ian

[Craig White]

When reading up on new Ford GT, they quoted it as having 20,000 lb-ft per degree, which is well known I expect.

The interesting part is the comment "that figure is twice the resistance to chassis twisting the original had."

Been reading with amusement the comments comparing DRB & RF torsional stiffness. At least I'll admit to being bias, so you already know my opinion if you check my signature. [img]/ubbthreads/images/graemlins/grin.gif[/img]

[Chris_K]

Fran-

Can you share any more details about the roof section (and by details I mean pictures)? What are the plans for the full cage as well, as in any more pictures?

Chris

[Fran Hall RCR]

I cant share any pics as the roof is being done by another company (not local) .Suffice to say that it is a replica of my fiberglass roof made over a buck supplied by me.

Roll cage wise I can supply a complete cage with no issues.
I have been working on a removable/swing out top door bar in the event of a roll over crash or heavy higher side impact.These parts are not production standard at this point but will be very soon...(our standards are high as you well know [img]/ubbthreads/images/graemlins/grin.gif[/img])

This I feel is an area where the GT roll cages fall short..
Cages can be built from any spec material(D.O.M or 4130) required for any racing sanction or just for added street safety.
All our cars com with a roll hoop as standard.

Feel free to call with more specifics....

[Chris_K]

Fran-

I see you're busy with the alu suspension... Any progress on the alu roof?

Chris

[Fran Hall RCR]

Lots of progress all around...thanks for asking [img]/ubbthreads/images/graemlins/grin.gif[/img]

I will gladly post pics when I feel the parts are ready for public consumption...