22 replies to this topic

[nosboy83]

What can you cut out of a mini shell to save weight when you have a 6 point cage with door bars?.

So far i have either done or is in the pipeline

f/g boot floor
f/g parcel shelf
f/g roof
f/g front end with no inner wings
Polycarb windows
10 ltr fuel cell
inner door frame (to avoid confusion i mean the bit that the winder mechanism is attached to)

Is it possible to remove the metal platform that the rear seats sit on or will that affect the structure to much?

cheers in advance

matt

[walks]

CLICK HERE

[nosboy83]

cheers for that i did a search but couldn't find anything.

so i can remove the rear bulkhead and the seat panel and door bins if i move the fuel tank forward of the front bulkhead (never thought of that before) but thats about as far as i can go.

Im a little worried about haveing the fuel tank so close to the engine what would happen in a front end smash if the tank ruptured?

[Sprocket]

Fibre glass is actualy just as heavy if not heavier than the steel panels

Carbon Fibre is what you want

Edited by Mini Sprocket, 31 July 2006 - 07:53 PM.

[nosboy83]

Fibre glass is actualy just as heavy if not heavier than the steel panels

Carbon Fibre is what you want

depends on the build of the carbon fibre panel. some carbon fibre can be as heavy a g/f depending on how its made

[Sprocket]

True but then i suspect you are talking about cowboy jobs. all depends how thick the skins are, glass is usualy thicker than the carbon to give it suitable strength.

Kevlar is the same weight as glass fibre for the same mass, but has high strength in compression and tension

carbon fibre is lighter than glass fibre for the same mass, but has high strength in compression. tensile strength is not as good as kevlar but better than glass.

Carbo kevlar is the best of both worlds high strength in tension and compression with reduced weight,

But then what do I know I only read a book

Also if your statement as true they would use more glass in aircraft for the non structural components as its far cheeper

[nosboy83]

True but then i suspect you are talking about cowboy jobs. all depends how thick the skins are, glass is usualy thicker than the carbon to give it suitable strength.

Kevlar is the same weight as glass fibre for the same mass, but has high strength in compression and tension

carbon fibre is lighter than glass fibre for the same mass, but has high strength in compression. tensile strength is not as good as kevlar but better than glass.

Carbo kevlar is the best of both worlds high strength in tension and compression with reduced weight,

But then what do I know I only read a book

Also if your statement as true they would use more glass in aircraft for the non structural components as its far cheeper

very true but im not talking about aircraft grade quality carbon. most if not all the places that produce carbon parts for minis cannot afford the large ovens needed to create the prepreg carbon fibre. This means they have to use wetlay techniques which produces generaly heavier mouldings.

I remember reading of a story iirc on minfinity in which two friends bought curley front ends at the same time. One was f/g and one carbon. When they weighed them they found the carbon front end was actualy heavier than the fibreglass one

[Sprocket]

Im surprised at that from Curleys

If thats the case then the racers would use glass, its cheeper.

Bu then thats was minifinity and were the same scales used in the same manor and did you witness these being weighed.


Irrespective of pre preg or not, the raw material carbon is lighter than the glass. so if its layed in the same manor the same amount of resin should be used, therefore comparable.

Prepreg is used in CRPs where high clamping forces are aplied to the moulding and the moulding cured in an Autoclave. This yeilds the highest strength and is how aircraft are built

Not doubting that there may be heavy carbon panels out there but then there are even heavier glass ones as well.

Its just that some thing does not ring true with the theory that carbon is heavier than glass, must just be down to bling factor if thats the case as why else would anyone want it.

Sorry not having a go, I just dont see sense

[nosboy83]

Im surprised at that from Curleys

If thats the case then the racers would use glass, its cheeper.

Bu then thats was minifinity and were the same scales used in the same manor and did you witness these being weighed.


Irrespective of pre preg or not, the raw material carbon is lighter than the glass. so if its layed in the same manor the same amount of resin should be used, therefore comparable.

Prepreg is used in CRPs where high clamping forces are aplied to the moulding and the moulding cured in an Autoclave. This yeilds the highest strength and is how aircraft are built

Not doubting that there may be heavy carbon panels out there but then there are even heavier glass ones as well.

Its just that some thing does not ring true with the theory that carbon is heavier than glass, must just be down to bling factor if thats the case as why else would anyone want it.

Sorry not having a go, I just dont see sense

dont worry i know your not having a go.

I pm,ed smudger a while back when i was looking at buying all the panels i mentioned before and asked what the difference in weight was like between carbon fibre and grp.

His responce was that there would be very little difference and in response to the whole curley carbon fron being heavy was "Hi, the reason his fronts weigh more is he uses LOTS of GRP in his Carbon Fibre Fronts, he uses about 4 layers of GRP to 1 Layer of CF cloth. If you want a very light weight front, then 1 layer heavy cloth and 1 layer of uni should be strong enough for you"

Im not saying carbon fibre is heavier its a fact that its lighter but due to alot of the building processes used weight differences are become negligable.
For me spending hundreds of pounds extra for very little or no weight saving seems a little pointless when i can use that part of my budget towards the engine or suspension For example a set of kad rear radius arms

[Wil_h]

I agree with NOSBOY, for pannels the differance between GRP and CF is very small, but it is mainly because of the way they are made. If you wanted to make a structural part then CF would be lighter.

When I got my GRP frontend it was really heavy. But it's much lighter now.

Also, don't remove the rear bulkhead, the back end of the car will just flop around. And if you fit a composite roof you will not be eligable for a hillclimbs/sprints in the saloon classes. Not sure if that's what you might be planning to do.

Wil

[GraemeC]

To go back to the original question - what is the car to be used for? A 6 point cage isn't going to put the strength back in from removing the parcel shelf and roof anyway, the body will still have flex from the floor pan upwards (unless you weld the cage in and stitch it to the A, B and possible C pillars).

If all out weight loss is the aim, regardless of rigidity, then you can remove the rear seat front lip, rear bins, lighten front and rear subframes, composite doors, composite boot lid (skin only), replace front bulkhead with alloy panel etc etc.

See the clicky link in my signature --->

[nosboy83]

hi thanks for all the replys.

Cheers Wil_h can't believe someone agreed with me on an internet thread!!! im going to have to print this of and have it framed because im sure its a first

Im planning on using the car for summer weekend and a bit of track use by the way.

so looks like im not going to remove the rear bulkhead. Im not to bothered about that because i wasn't to happy about having a fuel tank under the wing on a road car anyway.

by the way If i cut away the rear seat panel can i take it right back to the bulkhead?

GraemeC i checked out your project link yesterday and was pretty blown away by all the work you have done to the shell but im not sure if im going to that extent.

simply i just want to get the shell as light as i can whilst still being road legal and not end up blowing hundreds of £'s on getting that extra half a kg out of the shell when i could be spending it on the suspension or engine.

[Wil_h]

by the way If i cut away the rear seat panel can i take it right back to the bulkhead?

No, just cut it back to the heal board.

Other ways to remove weight:

- remove all the little tags that do nothing all over the car
- remove the headlining lip around the inside of the roof (well most of it.
- remove the rear seatbelt mounts on the C pillars
- remove all the dash rail and bits behind it (although you will need to replace this with a dash bar to mount the steering on, so might not save weight.

Wil

[nosboy83]

would reducing the rigidity of the shell badly effect the handling or is this more to do with what would happen in the event of a crash?

[Sprocket]

both