GRP monocoque based on steel car?

[singlecoil]

Anyone any thoughts on the idea of getting a steel-bodied car and making moulds to produce exactly the same thing only out of GRP. Obviously the panels would need to be thicker than the original steel ones, but is there anything inherently wrong with the idea? If all the external and internal panels were reproduced then it wouldn't need a steel chassis.

I'm not really looking for thoughts on whether the project would be worthwhile or not, just whether it would produce a viable car.

[singlecoil]

groomi said:

I can't see how something engineered to be made from steel will be strong enough if made from GRP. They are completely different materials with very different characteristics.

Not saying I disagree, but could you put some flesh on those 'bones'? I can think of a few cases where stuctures have been made in either material, and where the main difference is just the thickness

groomi said:

AFAIK the only all GRP mocoque car produced is the original Lotus Elite, but it's construction is very different to a steel mocoque car.

I think you'd need at least a steel backbone chassis to make it work.

Oh dear, the PH kit car forum is suffused with GTM owners who will want to disagree with you about the Elite being the only one!

[singlecoil]

rhinochopig said:

Wouldn't it be very heavy though? GRP is very prone to stress fracturing around risers - just look at the bolt holes on kit bodywork to see the crazing and cracks - unless it is very thick.

I guess the idea would be to reinforce areas where the stress was concentrated, and thicken the GRP in those areas too.



GRP is less sophisticated and less strong than carbon fibre/epoxy etc, but they make racing cars out of that stuff where weight is critical, and so it seems reasonable to think that a GRP car could also be sufficiently strong albeit heavier.

I've just rememebered, Murtayas are GRP monocoques too.

[singlecoil]

gtmdriver said:

I did it with my GTM coupe.

I replaced the steel chassis/tub with an exact replica made in GRP.

As you suggest I made it thicker than the original with kevlar reinforcement at all the pick up and mounting points.

It was also braced with wooden and RPU foam formers to produce box sections on all the flat panels.

When it was finished it was considerably stiffer (and straighter) than the original

That's really interesting. Do you have a build diary anywhere? And how did you manage with the suspension mountings etc?

[singlecoil]

gtmdriver said:

I have some build photos here.

And very impressive too! And all the more so when I looked at the before pictures at the end.

[singlecoil]

dcoombes said:

groomi said:

AFAIK the only all GRP mocoque car produced is the original Lotus Elite, but it's construction is very different to a steel mocoque car. .

Not to mention the Rochdale Olympic, ALL GRP, not even sub- frames for the engine or suspension mountings.

Try not to leave it another 45 months before making your next post!

[singlecoil]

Gnits said:

I could have sworn the S1 Elise was Aluminium monocoque - the vx220 certainly was.
Murtaya is indeed GRP and has a torsional stiffness of something like 14,000 nm per °

Elite, not Elise. Pistonheads, spelling matters, especially when it means it's a different car

http://en.wikipedia.org/wiki/Lotus_Elite

Edited by singlecoil on Friday 5th February 21:52