GT Forte chassis

[Marc Stevenson]

Has anyone here built a chassis from the GT Forte flat pack that used to be sold?
The square tubing is 1.5mm. Seems too lightweight to me?? I am not an engineer but have fabricated a lot of equipment over the years. I appreciate any input

 

[Mike Pass]

Check out this build log.

B

Thread 'Bob's GT Forte scratch build.'

Mar 18, 2015

Well the sun is out and I have finally made a start! The pile of metal I picked up yesterday is cutting nicely.
Thanks to everyone on this forum for providing the inspiration and no doubt the much needed advice and criticism in the future. Welding tomorrow!

• bobjmanchester
• Replies: 148
• Forum: GT40 Build Logs

Bob is local to me in the NW UK. He is not well and is selling the project. He has incorporated a lot of improvements to the chassis. If it is of interest to you and you want to save a lot of work and time send me a PM and I will pass on Bob's contact details.
Cheers
Mike

 

[Brian Kissel]

How much is a flat pack going for ??
Didn’t someone here in the states buy his deal ??

You are in the states aren’t you ??

 

[Mike Pass]

GTForte went out of business some time ago. I don't know what a flat pack cost. Bob built his chassis from the plans which if I remember correctly were about £350.
Cheers
Mike

 

[Kyle]

My frame design is 1.5mm or 1/16. Remember stiffness is in the width of the tubes. You’re after rigidity. If you F up enough to worry about 1/16 bending then you’ve got a bigger issue on your hands.

I had an engineer help with the design and we’ve gotten it to 7600lb/ft degree torsional rigidity so far. Shooting for over 10-12k.

 

[Mike Pass]

Hi Kyle, Can you tell us how you improved the chassis torsional rigidity (pics if possible). The usual is around 3,000 ft/lbs /deg. 7600 is a very good figure. 10 - 12 K would be very impressive. This info would be really useful for the many frame chassis builders here on the forum.
Thanks
Mike

 

[Andrew]

It would be interesting to understand the values on a Tornado/Southern/RF. Aircraft are built similar with an underlying structure (ribs, stringers, and longerons) with the skin taking a good deal of the load. I need to bust out some engineering books but I’d bet with some structural rivets at the right spacing a paneled space frame would be nearly as stiff as a mono.

 

[Mike Pass]

Here you go.
With some actual figures so you can see that one of the usual panelled frames is nowhere near a monocoque stiffness.

Thread 'Chassis stiffness article'

Jan 18, 2025

Here is an article I put together a while back for the GT40 Enthusiasts Club magazine. I have finally got round to posting on here.

Chassis torsional stiffness

I am not a structural engineer but here is my amateurs attempt to understand chassis rigidity, especially the GT40 chassis in it’s many variations.

There are two main types of chassis – monocoque and spaceframe. Monocoques are boxes made from sheet material. Spaceframes are lattices made from steel tubes.

The idea of a chassis is to be a rigid structure to which various components can be attached – mainly suspension, engine and...

• MikeP
• Replies: 2
• Forum: All Ford GT40

• 

Cheers
Mike

 

[Andrew]

Thanks Mike very interesting. I still assert with some careful bracing and proper rivets you can get close on a space frame. The key is to get the panels to take the load but this can’t be done without the proper rivets to carry said load. It’s why aircraft don’t use cheap pop rivets. I’d be curious to hear from AK or Tornado on if they have looked at differences in rivets and spacing during a build. When I build my car I’ll be doing the math and using aviation structural rivets. Likely the spacing will be much tighter than most I’ve seen.

 

[Randy Folsom]

It also depends on if the tubing is hot or cold rolled. Cold rolled is significantly stronger, and much easier to work with. Naturally, it also costs more. If you choose cold rolled, do your best not to minimize welding heat as too much heat will make the joints strength the equivalent of hot rolled. My guess is that Forte’s flat packs used cold rolled because the cutting process would be cleaner. It was much less expensive 10 years ago.

 

[Clayton]

Over 20 year old thread, but still has really good info on chassis stiffness

J

Thread 'Deflection Figures for a GT40 Chassis'

Jul 27, 2004

Does anyone have any idea of how stiff their chassis is in ft/lb/degs.

I believe a McLaren F1 is 25,000. a Porsche 911 is about 10,000.

It would be very interesting to know what figures we've all got.

Regards,

J.P

• James
• Replies: 77
• Forum: GT40 Tech - Chassis,Brakes,Tires,&Wheels

Clayton