Aluminium monocoupes and kit cars

[Sam_68]

mickrick said:

Getting back on topic, those Boys back in 1967 didn't do too badly with the ally tub of the type 49 and 400hp! Obviously that was a time when Men where Men, and Sheep where nervous!

I couldn't speak for the sheep, but you did miss one other important qualification:

'...and the monocoques were thrown away at the end of a season's work...'

See page 1.

[ceebmoj]

Lots of interesting replys while I have been away.

I have been spending some time with bits of card, scissors and the glue trying to make models of tubs that could be constructed using the means that I suggested. I have been having great fun and learning a lot I found this thread about rebuilding a mclaren M10 witch shows some mice details of the tub.

http://forums.autosport.com/index.php?showtopic=82...

I then tried the same sort of thing but using the methods as shown for the costin cars and made a mess but also learnt lots about other ideas I had been having also found the use of space for the fuel tanks interesting.

I have been thinking about building something that is fun but also fuel efficient for a while now and if I can get my head round this type of construction I also think that with some refinement it could be a good way to produce vehicles in low volume.

I will get some pictures of what I have been up to and post them so people cleverer than me can point out the obvios floors I have missed

[cymtriks]

Sam_68 said:

cymtriks said:

Sam_68 said:

I thought we covered that: cost.

Not convincingly covered.
Aston Martin?
Ferrari?
Lamborghini?

All of the above build cars in production numbers that effectively preclude carbon fibre.

'Aha!' Says Cymtriks, 'you said cost, you didn't say anything about large scale production difficulties!'

But, my dear chap, they amount to the same thing: if you want to build 50 cars a week (and it may surprise you to discover that even Ferrari builds twice that number), in theory there's nothing stopping you setting up a vast factory with rows of autoclaves and dozens of Italian tailors cutting patterns out of pre-preg for you, but the costs to be amortised would be absolutely astronomical.

There are a good few extremely limited production supercars that have used carbon fibre (Bugatti EB110, McLaren F1, KTM Crossbow, Bugatti Veyron, Ferrari F50 etc.), but at present the technologies have an economic 'glass ceiling' on production numbers.

cymtriks said:

If cost is the reason then how much are we talking about? Enough to rule it out for a car that sells on performance, is related to motorsport in the public view and costs well over 100K?

Yes, compared to the much cheaper technologies of extruded aluminium, which are sexy enough, cheap enough, light enough, stiff enough and vastly cheaper and more production-friendly.

It's anecdotal, I know, but I've been told by a very reliable source that the reason Westfield didn't produce more than 6 FW400's is that when they went back to place an order for the next batch of tubs after the initial prototype run, they were told that the cost would be such that it would put the price of the car into Porsche 911 territory. That's for a 'Seven', with an MGF engine... If CF makes a 'Seven' cost as much as a Porsche 911 (and if you have difficulty believing that, look at the price of the KTM Crossbow, and what happened to that, commercially), then how much is a carbon fibre 911, going to cost. And how much for a carbon fibre Ferrari 458?

Interesting stuff.

I would have thought that hand cutting wouldn't be required in production volumes of thousands a year as it would be worthwhile to automate it. and that autoclaves wouldn't be anymore expensive than some of the other equipment that manufacturers have such as panel press tooling or paint booths (which contain heating processes to dry the paint).

It may be that the quote for the FW400 was a polite way of turning down the business rather than a reflection of true costs?

Perhaps the best way forward would be to make a very simple structure using large diameter carbon fibre tubes thus offsetting the material cost with reduced labour and getting a worthwhile weight reduction.

[slomax]

An interesting bit of useless info regarding production lines and sheer volume. Castle brom jaguar/landrover produce about 50k+ cars a year. Consider that they have to shut down and maintain the machines every so often and they actually build cars for about 45 weeks of the year. They get about 7 hours of production in a day, 5 days a week. So that equates to a minimum of 1 brand spanking new car coming out of the complex every 1minute and 40 seconds.


I cannot prove any of this, but the figures sound kind of realistic, if a bit mind boggling. I was told this by a senior engineer at JLR last year in a lecture, so presume it is true.

[Sam_68]

cymtriks said:

I would have thought that hand cutting wouldn't be required in production volumes of thousands a year as it would be worthwhile to automate it. and that autoclaves wouldn't be anymore expensive than some of the other equipment that manufacturers have such as panel press tooling or paint booths (which contain heating processes to dry the paint).

You don't have to lay up breather membranes, vac bags etc. when you're spraying a car, and spraying can be done by robot, on a moving production line. To the best of my knowledge, nobody has yet managed to teach a robot to manipulate several layers of floppy fabrics and films into the correct orientation in a mould. I don't doubt it could be done, but you'd need a NASA-Mars-mission-like investment budget to develop and implement the technology. The costs of which would need to be passed on to the customer...

cymtriks said:

It may be that the quote for the FW400 was a polite way of turning down the business rather than a reflection of true costs?

Perhaps. But (and I'm just an 'umble 'ousebuilder, you understand) when someone gives me a stupid quote, my first reaction is to seek several competitive quotes from alternative subcontractors/suppliers.

But why settle for a simple explanation from a reliable source when a complicated and speculative one is available?

The more likely influence was that the Megabusa offered weight and performance not far removed from the FW's, with a steel spaceframe, for half the cost, and Westfield didn't exactly have an orderly queue forming for the FW at it's original list price.

Of course, they could have built a Hayabusa engined FW, which would have been even lighter and even quicker, if they could have got the tubs for a reasonable price. But they couldn't. So they didn't.

cymtriks said:

Perhaps the best way forward would be to make a very simple structure using large diameter carbon fibre tubes

I just knew it would only be a matter of time til we got round to ladder frames.

Edited by Sam_68 on Monday 15th November 18:19

[Sam_68]

ceebmoj said:

...I found this thread about rebuilding a mclaren M10

Nice link!

[seansverige]

Fascinating thread.

My engineering knowledge is only just sufficient to reveal the extent of my ignorance, but CF costs are coming down. The MP4-12C uses a CF chassis, is cheaper than the F458, and they hope to shift a couple of thousand p.a. - and it's set to become far more widespread: the BMW city car will use a CF body structure, and VW's L1 has a carbon chassis. (btw - anyone seen that video of an LF-A component being woven? Amazing)

Even if costs reduced, not yet convinced about large scale CF use: weight & therefore fuel saving by using a material that needs lots of nasty chemicals and energy in manufacture (as well as storage if we talking about pre-preg), and is only good for landfill at the end of it's life; is this really progress? (and is it not hugely ironic that driving the weight reduction is emissions / economy regs compliance - or just unintended consequences in full effect?) Someone will solve these problems at some point, but no-one's making this an entry criteria to mass-market use.

[Sam_68]

seansverige said:

The MP4-12C uses a CF chassis, is cheaper than the F458, and they hope to shift a couple of thousand p.a.

IIRC, the KTM X-bow was originally projected to sell in similar numbers to those originally anticipated for the Elise (about 500 per annum), but then it was originally intended to sell for circa £35K, rather than the £52K RRP it eventually listed at.

To be fair, it's a lot more complex structure than the FW, which originally listed at £35-£40K (depending on engine spec.) way back at the end of the last century, so in real terms prices would seem to be gradually reducing.

[Russ Bost]

Getting back to the original post re aluminium monocoques rather than composites which we've now got onto & are a whole different ball game .............

It would seem from some of the designs posted that once you get into 2 seats wide designs rather than the original "cigar tube" type designs of 70's F1's, that these are not true monocoques at all, but a monocoque mid section with subframes integrated front & rear, is this at least partially due to the difficulty of keeping the structure stiff as soon as it gets wider?

Given the different manufacturing techniques like laser cutting that are available now (so the holes are the right size & line up!), plus newer (stronger?) adhesives is there a realistic possibility that a single seat (or tandem style) arrangement might actually work quite well as a modern design if all the joints were bonded as well as rivetted, surely this would help to stop the loss of stiffness which has been mentioned as a major drawback for production over the throwaway mentality of the racer?

[singlecoil]

I've become fascinated with the idea of making a 7 type vehicle as a monocoque. I've done a google image search but not come up with anything on the FW400, it would be interesting to see a picture of the basic chassis, if anyone has one?

I'd be tempted to do a prototype in birch plywood, just to sort out how all the bits would fit together. I've done some research on aluminium honeycomb panels, and found out how they are cut and joined, but nothing yet to give an indication of price, and I don't know enough about engineering to know what thickness of panels I would need in the various different areas.

[Joe T]

I had a good look at the Chesil Aluminium/Composite chassis at the NEC at the weekend, didnt get a chance to speak to any of them.

Looks interesting, looked like it was made up of lasercut sections bonded together.

http://www.autoevolution.com/news/inrekor-unveils-...

[ceebmoj]

Russ Bost said:

Given the different manufacturing techniques like laser cutting that are available now (so the holes are the right size & line up!), plus newer (stronger?) adhesives is there a realistic possibility that a single seat (or tandem style) arrangement might actually work quite well as a modern design if all the joints were bonded as well as rivetted, surely this would help to stop the loss of stiffness which has been mentioned as a major drawback for production over the throwaway mentality of the racer?

The paper models I have been making inspired by the Mclaren M10 tub pictures posted earlier, seam to show that I can make a single seater chassis rapidly and for a sensible price using this method. I think the next step that i'm going to try is to have a go at a 1/6 scale tub in aluminium. bonding and riveting it all together. However I still want to see lots more pictures of tubs being restored or constructed to see what else I can learn.

[Stubby Pete]

singlecoil said:

I've become fascinated with the idea of making a 7 type vehicle as a monocoque. . . . .

I repeat, The Quantum Xtreme uses a stainless steel monocoque.

[singlecoil]

Stubby Pete said:

singlecoil said:

I've become fascinated with the idea of making a 7 type vehicle as a monocoque. . . . .

I repeat, The Quantum Xtreme uses a stainless steel monocoque.

And? Am I missing something?

[Sam_68]

singlecoil said:

I've done a google image search but not come up with anything on the FW400, it would be interesting to see a picture of the basic chassis, if anyone has one?

There was a press release picture of the naked rolling chassis in the magazines published around the time of the car's launch, but I've only ever seen it reproduced at quite small size, so it won't be much use to you.

I've got a few of mine, which I'll try to upload later, but some of the detail is obscured by the scuttle and the radiator duct at the front.

If you want specific details, let me know - I've got the bodywork off and the car up on axle stands at the moment, anyway, to do a bit of tidying up over the winter, so I should be able to get shots of most bits quite easily.

Having said which, there's really not all than much to see - it's quite a simple structure.

ETA: Just found one that might be usuful on my work computer:



That's the rear of the chassis, showing the fuel tank, rear ARB and back of the Hewland.

Edited by Sam_68 on Tuesday 16th November 13:09

[skwdenyer]

Joe T said:

I had a good look at the Chesil Aluminium/Composite chassis at the NEC at the weekend, didnt get a chance to speak to any of them.

Looks interesting, looked like it was made up of lasercut sections bonded together.

http://www.autoevolution.com/news/inrekor-unveils-...

Since my doctoral research was on sandwich panels, I'm relatively comfortable to comment on this. Inrekor have not, really, invented anything new at the material level. Foam-filled, aluminium-skinned sandwich panels have been around for 50 years. They are used extensively in all sorts of places.

What Inrekor appear to have created is somewhat analogous to Gordon Murray's 'iStream' approach: a platform-as-a-system approach to car design, allowing a core set of design elements and approaches to be used to solve customers' chassis problems in a proven, efficient way. You or I could design the same solution using the same materials, but Inrekor have done a lot of the intellectual heavy lifting already.

There is no difference between what Inrekor are doing and what, say, racing car designers were doing 30 years ago with similar materials. They have simply productionised the techniques in such a way as to make them potentially viable in higher-volume applications.

To tie this in with the OP's thread, Inrekor are not delivering a monocoque of any kind

[Mr2Mike]

skwdenyer said:

To tie this in with the OP's thread, Inrekor are not delivering a monocoque of any kind

I don't think that was suggested. I only mentioned it as the conversation was steering towards composite materials in general for chassis construction rather than monocoques specifically.

[skwdenyer]

Mr2Mike said:

skwdenyer said:

To tie this in with the OP's thread, Inrekor are not delivering a monocoque of any kind

I don't think that was suggested. I only mentioned it as the conversation was steering towards composite materials in general for chassis construction rather than monocoques specifically.

Sorry, I did realise that; I was just trying to steer things back before we ended up covering every possibly construction method under the sun!

[ceebmoj]

skwdenyer said:

Mr2Mike said:

skwdenyer said:

To tie this in with the OP's thread, Inrekor are not delivering a monocoque of any kind

I don't think that was suggested. I only mentioned it as the conversation was steering towards composite materials in general for chassis construction rather than monocoques specifically.

Sorry, I did realise that; I was just trying to steer things back before we ended up covering every possibly construction method under the sun!

Maby my initial question should have been more open ended regarding why we don't see a wider variety of construction methods used in kit car chassis. I guess I was interested in why as the cost of a variety of macheanumg methods become more cost viable we dont see other aproches being taken more.

[mickky3]

Hi
Ive been looking for some pics of alloy mono chassis, and ive just found this
this site, and thread. So Ive just joined PistonHeads. I hope you are intrested in my project. If anyone has any pics of alloy mono chassis I would love to see them. my addy is [e-mail]

Im buiding an alloy mono chassis for my GT40. most of it will be made from 16 SWG 6082T6, riveted, and bonded, with Araldite A420. The same adhesive used in the
manufacture, of both commercial, and Aircraft spec, alluminium honycomb

It wont be as heavy as a steel space frame, but that is not the main reason for building it. The main reasons are

1 It wont need painting, 6082T6 has good corrosion resistance

2 A space frame needs to be pannelled in afterwards, adding weight, and can
take a lot of time , and effort to do it correctly

3 Ease of manufacture. I have designed the chassis so most of the bends are 90
degrees, so by useing alloy extrusions, T section, Angle section, and Square
hollow section, there wont be a lot of bending to do. So most of it can be done
in a home workshop, with a pillar drill, and general hand tools. There will be
a small amount of TIG welding required. All the materials can be bought
online from Aalco Metals , or Parker Steels

The Idea is to make a kit form type chassis, that any compitant, engineer
could make, it is not a project for an inexperianced person....I have been
researching, the project for about a year. Most of my information came from
internet. A good understanding of material properties ie, Yeild Strength,
Tensile Strength, "Hooks Law", Youngs Modulas, Stiffness etc, should be
obtained before starting. I can give links to these, and other articles, on
riveting etc.

Getting strength from an alloy mono chassis is not a problem, but getting
chassis Stiffness, without excessive weight, is more comlicated...

I have started building the main tub, and I will post some pics. (if that is possible, and allowed, on this site) in about 2-3 months