Bits of bent metal tube and a Mig welder - as the Meerkats would say “Simple”
OK having roughed out a chassis design on that olde fashioned stuff made from trees, love 'puters can't used cad to save me life.
I had the 'bright idea' to construct a life sized model out of plastic waste pipe...to check I could actually clamber my 'airodynamic
butt' into and out off, all good so far.
Then the Eiphany struck me...or was it the Mrs
why not take the plastic waste pipe space frame chassis model, and wrap it in layers of GRP, then panel it with GRP sheets
hay Ho one strong light weight, death trap, or excellant chassis.
Am I going nut's, has the plot up and left, or has this potential, or has someone already done it read the book got the T shirt?
Thanks for any and all opinions
erm, not GRP, i'm pretty sure, if you put on say a 3mm layer round a pipe, then stood on it, it would break
carbon might work, perhaps, but will have to be done properly, exactly what 'properly' is, i don't know, but would probably involve
baking it in an autoclave, vacuum bagged etc.
[Edited on 17/8/11 by blakep82]
design for stiffness , the strength will automatically be there .
check out pultruded tubes .
GRP would be a no no as it has no inherent consistency in tensile or torsional strength. Yes it's strong as a layered product and will diffuse
impact as it absorbs the shock by breaking and distorting uniformly. So good bodywork, floor pan etc. but not so good structurally. Carbon fibre needs
to be formed and layered or wrapped in the direction of stress. You can make a prop shaft from carbon fibre as long as you don't want to reverse
coz the shaft will just unwind its own carbon wrap. As Blakep says you will need an autoclave to go from pre-preg -> mat to finished carbon
component.
Bits of bent metal tube and a Mig welder - as the Meerkats would say “Simple”
Ok not the answer I wanted, but the one i was expecting 
pultruded tubes look interesting if expensive and a bit complex,
so indeed it looks like back to the bent metal tube and mig welder option
Thanks all
quote:
Originally posted by PeterV
You can make a prop shaft from carbon fibre as long as you don't want to reverse coz the shaft will just unwind its own carbon wrap.
Errrm - i thought this bloke called Colin, can't remember his name made a few GRP cars. They seemed to do ok. Now what was that Chap, man i
can't remember his name 
quote:
Originally posted by MikeR
Errrm - i thought this bloke called Colin, can't remember his name made a few GRP cars. They seemed to do ok. Now what was that Chap, man i can't remember his name
quote:
Originally posted by indykid
It must struggle to deal with engine braking loads then....
quote:
Originally posted by PeterV
GRP would be a no no as it has no inherent consistency in tensile or torsional strength. Yes it's strong as a layered product and will diffuse impact as it absorbs the shock by breaking and distorting uniformly. So good bodywork, floor pan etc. but not so good structurally. Carbon fibre needs to be formed and layered or wrapped in the direction of stress. You can make a prop shaft from carbon fibre as long as you don't want to reverse coz the shaft will just unwind its own carbon wrap. As Blakep says you will need an autoclave to go from pre-preg -> mat to finished carbon component.
Bits of bent metal tube and a Mig welder - as the Meerkats would say “Simple”
quote:
Originally posted by MikeR
Errrm - i thought this bloke called Colin, can't remember his name made a few GRP cars. They seemed to do ok. Now what was that Chap, man i can't remember his name
Yes twybrow completely right
The thing about design is the choice of material and understanding its properties is where you start true of space frame and what is loosely called
GRP or Composites.
A glassfibre monocoque amateur car is completely possible. The advantage is that with a piece of metal it has to be big enough throughout its whole
length to carry/absorb the largest load applied to any part of it. In a laminate the thickness and structure varies through the component depending on
the loads applied.That is where the weight is saved.
The thing is if you get it wrong in design or in quality of hand laminating practice nobody can tell until it starts to fail by cracking/fracturing
Look at the road cars produced by God Colin Chapman in the 60s.
I wonder how the use of composites in stress bearing applications would be viewed by IVA but it would be a great step forward especially in BEC
applications.
Can we have a Laminate and laminating area in the forum ChrisW
PS we were talking about amature "wrapping" product around plastic tubes not a cad/cam layup design
We work for companies that supply materials for LM's GT's and F1's, racing yatchs and aircraft, we supply all the kit that measures the
process from start to finish, so yep everything is possible if you have a blank cheque book 
quote:
Originally posted by twybrow
quote:
Originally posted by PeterV
GRP would be a no no as it has no inherent consistency in tensile or torsional strength. Yes it's strong as a layered product and will diffuse impact as it absorbs the shock by breaking and distorting uniformly. So good bodywork, floor pan etc. but not so good structurally. Carbon fibre needs to be formed and layered or wrapped in the direction of stress. You can make a prop shaft from carbon fibre as long as you don't want to reverse coz the shaft will just unwind its own carbon wrap. As Blakep says you will need an autoclave to go from pre-preg -> mat to finished carbon component.
Bits of bent metal tube and a Mig welder - as the Meerkats would say “Simple”
What a load of tosh! No disrespect, but that is utter tripe. Sorry to sound patronising, but composites are more complicated than a few blanket statements!
Having worked extensively on designing/manufacturing major structural components in glass, carbon, aramid etc, the fibre type is only one of many points to consider. The layup, the stress orientation (as you rightly said), the manufacturing method, etc, etc etc, all contribute to a components ability to do its job. Mr Chippy is bang on - they are a different beast in terms of the design. And not all prepregs need autoclave curing - in fact some will see little or no performance improvement by doing so. There are even prepgregs that will cure at ambient temperature, or even under a UV light.
Your comments on propshafts are also misinformed, or at the very least there would a lot of unhappy Nissan GTR owners (all Carbon props)! Methods have moved on a bit since just wrapping - that is fishing rod technology (but it does have a purpose). I have 1st hand experience of propshafts made for actuation on very large aircraft. These were designed to have a service life of 30 years, and could take 1200ft/lbs, and they had a wall thickness no more than ~2mm (look closely at my car photos, and you may spot a piece!). They ran forwards and backwards with virtually the same load....
Mr Tribble, I would say, if you aren't sure, or have no prior experience, a structural component (chassis) is not the best place to learn! You would want to design specifically with composites in mind - copying a structure currently made from metal will never see you getting the most from the benefits from the material type. However, with some reading, some testing and some nifty design, you may well be able to make something - the question would be if it is worth it...?
putting aside all the arguments - here is someone who did much the same but with carbon fibre for his push bike, turned out very well but looks plenty
of work
linky
As some comments above, if you design the chassis with composites in mind, and GRP in particular then it could work.
Just using a space frame chassis in plastic tube and wrapping it up won't be ideal.
Look at the monocoque of the mini marcos I had as an example. Its very flimsy, the only internal structure is a couple of two-by-fours full length
which are wrapped in a small amount of grp. But as they are part of a complete shell, the monocoque is surprisingly strong.
So if you were to use the plastic pipe to give you the outline of a shell, wrap in grp, block foam between all the spars, then skin both sides, that
would be a good start of a grp chassis.
Thanks for all the thoughts Gents.
Didn't realise there are prepregs that could cure at room temp's
and Mr Whippy thanks for that link kinda insperational.
And please no arguments on acount of me...I've a large number of ideas about building cars...now GOOD ideas that's a lot smaller number
ah Balidey you've just described much better than me what I was thinking of
[Edited on 18/8/11 by TheGiantTribble]
quote:
Originally posted by twybrow
quote:
Originally posted by PeterV
GRP would be a no no as it has no inherent consistency in tensile or torsional strength. Yes it's strong as a layered product and will diffuse impact as it absorbs the shock by breaking and distorting uniformly. So good bodywork, floor pan etc. but not so good structurally. Carbon fibre needs to be formed and layered or wrapped in the direction of stress. You can make a prop shaft from carbon fibre as long as you don't want to reverse coz the shaft will just unwind its own carbon wrap. As Blakep says you will need an autoclave to go from pre-preg -> mat to finished carbon component.
Bits of bent metal tube and a Mig welder - as the Meerkats would say “Simple”
What a load of tosh! No disrespect, but that is utter tripe. Sorry to sound patronising, but composites are more complicated than a few blanket statements!
Having worked extensively on designing/manufacturing major structural components in glass, carbon, aramid etc, the fibre type is only one of many points to consider. The layup, the stress orientation (as you rightly said), the manufacturing method, etc, etc etc, all contribute to a components ability to do its job. Mr Chippy is bang on - they are a different beast in terms of the design. And not all prepregs need autoclave curing - in fact some will see little or no performance improvement by doing so. There are even prepgregs that will cure at ambient temperature, or even under a UV light.
Your comments on propshafts are also misinformed, or at the very least there would a lot of unhappy Nissan GTR owners (all Carbon props)! Methods have moved on a bit since just wrapping - that is fishing rod technology (but it does have a purpose). I have 1st hand experience of propshafts made for actuation on very large aircraft. These were designed to have a service life of 30 years, and could take 1200ft/lbs, and they had a wall thickness no more than ~2mm (look closely at my car photos, and you may spot a piece!). They ran forwards and backwards with virtually the same load....
Mr Tribble, I would say, if you aren't sure, or have no prior experience, a structural component (chassis) is not the best place to learn! You would want to design specifically with composites in mind - copying a structure currently made from metal will never see you getting the most from the benefits from the material type. However, with some reading, some testing and some nifty design, you may well be able to make something - the question would be if it is worth it...?
Hi baliday the problem long term with the marcos shell was the wood combined with GRP the GRP has no chemical adhesion to the timber just mechanical
because of the shape and when the damp gets to the wood it swells up and damages/weakens the laminate we used to have the same problem with Fletcher
Speedboats this is compounded by the fact that GRP is only waterproof whilst the gel coat is intact when the water gets in "osmosis" the
strength is lost.
If we build this car other combinations of materials are better.
Even the gelcoat is porous, that's how most of the osmosis occurs.
The best solution for a boat is to coat with epoxy first, then prime with epoxy based primer, and paint under the waterline.
Similarly, epoxy is the ONLY resin I would use to build a car. Much tougher than poly and less brittle, and better adhesion to the fibres and any core
materials.
I still wouldn't build a composite car. Except maybe using carbon, a good phenolic, aramid or ali honeycomb, and an autoclave to do the job. Seen
and been asked to fix more than my share of half arsed bodges, some from well known names!
Cheers,
Nev.