Blatman Posted October 25, 2001 Share Posted October 25, 2001 V7 Have a wild guess..........id=limegreen> Link to comment Share on other sites More sharing options...
V7 SLR Posted October 25, 2001 Share Posted October 25, 2001 Heh heh, no wonder you're a happy man then. smile.gif I hadn't made the connection, but I have seen the car. Congrats. It's a fearsome beast, and beautifully screwed together. Link to comment Share on other sites More sharing options...
R2D2 Posted October 25, 2001 Share Posted October 25, 2001 I think this post started out with comments about the stiffening effect of the alloy skins on the basic spaceframe. I tend to think that the stiffening effect of the alloy skin must be fairly small and the original description that Lotus used was "semi-stressed skin". It seems to me that anything that is described in this way must be a bit dubious and designed to increase sales appeal without too much engineering credibility. (I have seen the DeDion suspension on a seven described as semi-independent and I have still to work out the semi-helical gearbox.) The stiffness increase that a single sheet of light gauge aluminium adds to a spaceframe structure must be limited to the stiffness of the panel providing that it will transfer load into the frame through the rivets/adhesive joint and a flat skin is really not very stiff at all. Chapman worked in the aircraft industry at the time he designed the Seven and stressed skin aircraft structures were well established by that time but the skin of the Seven is not really stressed until some deformation has occurred. I think that in the order of importance the floor has the most effect, followed by the inner panels and then the outer panels, which probably have negligible effect. (I would worry about carbon inner panels as if the car had a serious accident the inner panels could well fail in a brittle manner and cause some nasty injuries.) Carbon panels should be stiffer than an similar aluminium panel as the Modulus of CF is higher than aluminium but some thought needs to be given to the direction the fibres are laid in if the Modulus is going to be uniform in all directions. I think that this means that replacing aluminium with CF will make the resulting structure slightly stiffer but again I do think the changes would be marginal and not worth worrying about. The comments about kevlar/carbon/nomex panels are worth thinking about because most F1 monococoques are made from these mixtures as were the bodies of Group B Rally cars. The outer layers of Kevlar are used to give high levels of impact resistance (Kevlar is commonly used in body armour and current motorcycle clothing)and would make much tougher outer body panels and much better accident protection. I think the comments about floor pans coming loose is very worrying. I would try to remove the panel and refit with a high quality aircraft adhesive (Loctite and CIBA-Geigy make some excellent products used in airframe, railway carriage and Lotus Elise manufacture) I would use a stronger rivet but not only the pulling force but I would look at the size of the rivet head to reduce the contact stress on the panel. If you use a steel rivet of standard size it may damage the aluminium unless load is spread by a washer. Tucker fasteners have a PDF downloadable catalogue which gives sizes/forces of their entire range. Bolting seat rails to the aluminium panels is frightening and if it is pulling rivets loose must be pretty crappy. I have just fitted new Kevlar/carbon seats in my rally car and the Blue Book regs are quite demanding and possibly worth looking at. I would certainly consider Ian's mod where he has used adapters to pick up the original mounts in the spaceframe tubes. Link to comment Share on other sites More sharing options...
V7 SLR Posted October 25, 2001 Share Posted October 25, 2001 I don't actually think I've pulled the rivets out, more that I've worn away their heads (such a fat git) on bumpy Scottish roads. Anyway, I do accept that bolting the seats to the floor is a crap idea, and one which I wasn't too pleased about when I put the car together. I did it though simply assuming others had and they were alright. Even assuming the seats bolted to the floor is not the cause of my floor coming loose, I think I will make some modifications to pick up the rear spaceframe mounts. Ian, is this what you have done? Can you email any pictures please? Thanks. See, I told you it was worth waiting for Chris. It is interesting to note that CF outer panels may slightly increase stiffness (assuming the outer skin partially increases chassis stiffness - I'm one who doesn't believe the Se7ens has a stressed skin too), but more reassuring to note that they probably wouldn't decrease it. If this is so, and the fact that CF replacements would be no heavier, I'd be happy to replace outer panels with CF if for no other reason than they're less easily damaged. Link to comment Share on other sites More sharing options...
gee_fin Posted October 25, 2001 Share Posted October 25, 2001 Depends on the type of carbon used. The nose-cones and rear wings I've seen on Caterhams are pretty damn thin, a high-speed pebble would rip a hole through them. I assume they're just a couple of layers of wet-lay - push your thumb into a nose-cone or the top of a wheel arch, then compare it to some pre-preg carbon. Granted they're bloody light though. Graeme. ________________________________________________________ graeme finlayson / gear cruncher / fluke motorsport graeme.finlayson@vicorp.com / www.fluke-motorsport.co.uk Carbon-fibre sale bonanza! Link to comment Share on other sites More sharing options...
V7 SLR Posted October 25, 2001 Share Posted October 25, 2001 Actually the Caterham nose and wings fend off small debris quite well. I've not had any failures due to anything hitting the car... ... but the car hitting tyres... well that's another matter. I've bust one rear arch (completely) last year, and one front one this year. Both times when some idiot placed the tyre wall right where I thought the racing line was. blush.gif As for weight though, you're right, they are VERY light. Someone pointed out to me, when I complained that my nosecone deformed when I prodded it with my finger, that if was any stiffer, it would have been heavier. I think he had a point. Edited by - V7 SLR on 25 Oct 2001 15:51:42 Link to comment Share on other sites More sharing options...
EFA Posted October 25, 2001 Share Posted October 25, 2001 Graham. Did somebody actualy make a special tool for your bodyshell? or is your car wet layup? I would say any structural improvement carbon panels give, unless they are inflexible and in compression or stress is minimal. Anything with a curve (i.e the side panels and rear skin) add only stiffness under stress load, not compression. In the real world, the floor and rear bulkhead are the only panels of a Caterham worth considering as adding any rigidity to the chassis. In order to make the floor stiff enouigh to make any effect it had to be made 2.0mm thick, and the side panels on the car were consequently specially fromed by Arch to take this additonal size into consideration. Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
gee_fin Posted October 25, 2001 Share Posted October 25, 2001 Depends on manufacturing process involved - wet-lay vs pre-preg. Cheap vs expensive. Quick vs time-consuming. I'll dig out the weights for each, erm, laptop is at home, will have to be Monday (shut it you lot wink.gif). ________________________________________________________ graeme finlayson / tyre burner / fluke motorsport graeme.finlayson@vicorp.com / www.fluke-motorsport.co.uk Carbon-fibre sale bonanza! Link to comment Share on other sites More sharing options...
gee_fin Posted October 25, 2001 Share Posted October 25, 2001 Arnie, The complete shell on my car is oven-moulded pre-preg carbon-fibre/kevlar/nomex, not wet-lay. This means there must be a mould somewhere. However, it's all been shrouded in a bit of mystery due to the copyright issues that followed from a short-sighted few in the midlands. Not entirely sure about every aspect of it as I haven't delved too deeply, rumours of various levels of large auto-clave access and things like that. I know who got it made and where to go to get things made/fixed should I need to but that's about it, I'm sure he could tell me the source but then he'd probably have to kill me smile.gif Graeme. ________________________________________________________ graeme finlayson / monkey wrestler / fluke motorsport graeme.finlayson@vicorp.com / www.fluke-motorsport.co.uk Carbon-fibre sale bonanza! Link to comment Share on other sites More sharing options...
EFA Posted October 25, 2001 Share Posted October 25, 2001 Whoever made that tool must have made a massive loss! a carbon tool for a body unit the size of that on a W*******d would cost about £20k Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
gee_fin Posted October 25, 2001 Share Posted October 25, 2001 Yep, shame it was curtailed prematurely. Whoever buys the car from me better give me first refusal should they wish to sell it on in the future, because if I have the cash I'd buy it straight back. ________________________________________________________ graeme finlayson / tyre warmer / fluke motorsport graeme.finlayson@vicorp.com / www.fluke-motorsport.co.uk Carbon-fibre sale bonanza! Link to comment Share on other sites More sharing options...
Blatman Posted October 25, 2001 Share Posted October 25, 2001 Graeme I'd be happy to look after it for you. It'd be nice to have two of Mick's marvels in the garagewink.gif V7 I hadn't made the connection, but I have seen the car. Congrats. It's a fearsome beast, and beautifully screwed together. Why thank you sir. I have to say that I had my reservations about the colour, but the rest of it is, as you rightly say, so nice I couldn't really say no. I've had it just over a year, and about 5000 miles, and it hasn't missed a beatthumbsup.gif Edited by - Blatman on 25 Oct 2001 17:01:58 Link to comment Share on other sites More sharing options...
ian balson Posted October 25, 2001 Share Posted October 25, 2001 V7, I'll get the digital camera out tonight. Regards Ian. Link to comment Share on other sites More sharing options...
EFA Posted October 25, 2001 Share Posted October 25, 2001 Graham, My only concerm would be risk of damage if there is no tool available..... Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
V7 SLR Posted October 26, 2001 Share Posted October 26, 2001 Ian, I got your piccies. Thanks very much. That's a good piece of engineering you've designed there. It's got me thinking how I should do mine now. Cheers. Link to comment Share on other sites More sharing options...
gee_fin Posted October 29, 2001 Share Posted October 29, 2001 Arnie, If there ever was any damage I know who/where can fix it, it's just all a little hush hush for now wink.gif ________________________________________________________ graeme finlayson / overdrafter / fluke motorsport graeme.finlayson@vicorp.com / www.fluke-motorsport.co.uk Link to comment Share on other sites More sharing options...
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