GT6_sleeper Posted November 6, 2009 Share Posted November 6, 2009 if your going to so much trouble why not look at a full space frame to replace the full chassis? Link to comment Share on other sites More sharing options...
gt5r Posted November 6, 2009 Share Posted November 6, 2009 if your going to so much trouble why not look at a full space frame to replace the full chassis? Really wish I'd gone that route - if I bend it I will produce a completely new chassis - infact bugger it I will for phase II - which is 450bhp T5 lump - think I might need it though ;D ;D Link to comment Share on other sites More sharing options...
mark spit Posted November 6, 2009 Share Posted November 6, 2009 A couple of years back, John Thomason had a TSSC mag report which was about someone who looked into the torsional flex of a bare Spitty chassis and measured the rigidity of it. Might have been an engineering student thesis or something??? They then added something to the top but off the top of my head I can't remember what but it made a massive difference. I'll have a copy somewhere but got no idea where, and prob no time to find it for a while either Won't help your designing but should give some clues. Yours Mark Link to comment Share on other sites More sharing options...
spitNL Posted November 6, 2009 Share Posted November 6, 2009 I have seen that too, but I don't think you would want that in your car. Link to comment Share on other sites More sharing options...
gt5r Posted November 6, 2009 Share Posted November 6, 2009 A couple of years back, John Thomason had a TSSC mag report which was about someone who looked into the torsional flex of a bare Spitty chassis and measured the rigidity of it. Might have been an engineering student thesis or something??? They then added something to the top but off the top of my head I can't remember what but it made a massive difference. I'll have a copy somewhere but got no idea where, and prob no time to find it for a while either Won't help your designing but should give some clues. Yours Mark Yeah JD posted a link on here recenlty - can't remeber where though - seem to recall what made the difference was a longitudinal brace from the rear cage to the front - I've a copy at home - Jd can you point us in the direct of your post/link?? Link to comment Share on other sites More sharing options...
spitNL Posted November 6, 2009 Share Posted November 6, 2009 http://www.computerfix-mobile.co.uk/img/Chassis_Stiffness_Issue_273a.pdf Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 Thanks! Link to comment Share on other sites More sharing options...
gt5r Posted November 6, 2009 Share Posted November 6, 2009 Dave - have you thought about filling the chassis with expanding builders foam - can't seem to source the stuff they use in strengthening boats atm - but builders foams has similar properties - going to do that to mine - minimal weight but might offer some form a resistance to twist google 'Sandwich plate system' - long term I'm making a second alloy floor and honey combe it the fill it - Andy on this board can you give a spec/source for this material used in SPS type work - ta ps - been doing a bit of thinking out of the box - but unfortunatly had to do some work at work today so not much posting!!!! Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 I could add another cross-member between two front outriggers as my sump has a deep relief in it that would normally allow the exhaust to hug tightly against the crank. Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 No Mark hadnt thought of that. My doors and bootlid are sandwich construction. Thin wall > Honeycomb/Foam > Thin wall. They are incredibly stiff you can stand a 14 stone man on the door skin bang in the middle and it won't break. Bootlid is 10x as stiff as a normal steel one without the support frame fitted. Maybe thats reliant on it being a good laminate structure? You know the whole lot is bonded down and laminated forming a stiff panel aircraft wings are the same on stunt planes just carbon fibre skinned. Not sure how it would react within a chassis. I think are loads are too great and the movement is too minimal? If you could start from scratch a carbon chassis using sandwich construction would be the way forward but using it in a crusty old chassis... I've given it more thought too. Link to comment Share on other sites More sharing options...
gt5r Posted November 6, 2009 Share Posted November 6, 2009 Interesting stuff though - going to give it a go up the front end and see what happens?? funny my chassis actually came off a 1981 spit which had 21k on the clock and was asre ended - picked it up in 1989 - its been dryed stored ever since - so its pretty mint inside and out - but like most things good they really don't deserve to go on concours cars and should end up wrapped around some armco I say(stars)(stars) Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 Who is going to build their own private test rig first though? I need to read that pdf again. I used a 1981 chassis on my first spit, was mint, original paint still shiney...That car was well solid. Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 Anyone know any basic free software that does stress analysis / build a model of the chassis then run tests on it... I know its a tall ask? Link to comment Share on other sites More sharing options...
AJ.Lintern Posted November 6, 2009 Share Posted November 6, 2009 Don't know of anything free - but have FEA software at work which would do the job. Just need a model - got any drawings of the chassis? Or were you just going to get your tape measure out? Link to comment Share on other sites More sharing options...
PeteClan Posted November 6, 2009 Share Posted November 6, 2009 I wouldn't recommend the expanding foam from DIY stores. People have tried it and whilst it doe give additional stiffness it also holds water so accelerating rusting. Pete Richards Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 Obviously AJ, I sleep with these diagrams under my pillow just waiting to whip them out at any moment. Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 so youre the man, busy at work? Link to comment Share on other sites More sharing options...
spitNL Posted November 6, 2009 Share Posted November 6, 2009 Free basic CAD software yes, but one that does FEA as well, no... Perhaps one of these, but I don't have experience with any of them. http://www.freebyte.com/cad/fea.htm FYI I did start on modelling the spitfire chassis in Solid Works, but my computer was too slow. : You really need a fast dual or quad core pc, especially for the stress analysis. F. Link to comment Share on other sites More sharing options...
AJ.Lintern Posted November 6, 2009 Share Posted November 6, 2009 I think foam only has a meaningful effect on thin-skinned structures where you need something to maintain the section. It relies on a good bond between the surfaces or it does nothing. Would maybe help a very thin walled steel box section, but not something you'd find in a Spitfire chassis. Link to comment Share on other sites More sharing options...
AJ.Lintern Posted November 6, 2009 Share Posted November 6, 2009 Oh trust you to have the drawings at the ready! Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 Take a while on a laptop then or my old Athlon XP1800? overclocked to 2200+! Link to comment Share on other sites More sharing options...
spitNL Posted November 6, 2009 Share Posted November 6, 2009 I used those too, but they are not detailed enough. Problem is the bends, of which there isn't any information on there. Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 I am prepared for a long-term project on this My turret bars can only go backwards in a fixed location bar that its a blank canvas. Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted November 6, 2009 Author Share Posted November 6, 2009 You can scale up the drawing can't you, work from it? I once scaled up a small drawing of a radio controlled aeroplane, I was about 10 years old It was an A2 page diagram I redrew it by hand into full size A1 sheet drawing and built the plane from it...It did fly briefly before I crashed it ;D Link to comment Share on other sites More sharing options...
Nick Jones Posted November 6, 2009 Share Posted November 6, 2009 Don't know of any free software - sorry. That kind of thing tends to be fiercely expensive. Wouldn't surprised if somewhere on here has access though.... That's a good article - thanks for that link Frederick. I met Ian Horsfall at Castle Coombe a while back and we talked about CV conversions.... very knowledgable guy. Interesting that comment about the extra cross member at the rear - I have several times toyed with the idea of linking the rear outriggers on the Vitesse - which would be the same thing. The Vitesse side rails are pretty weedy - were I replacing I would use proper box section and box the front and centre outriggers. I have also thought about making proper sills to tie the front and rear sections of the tub together properly and linking them in properly with the chassis centre rails. People froth at the mouth when you talk about welding body and chassis together, but in fact, provided you have everything lined up first and can't really see any major downsides and it will force the two sturcture to function together rather tahn semi-independently - which has got to help stiffness. For me though this is all part of a project which doesn't exist (yet). The Vitesse is a floppy old thing - which is why I don't bother with stiff springs! On a Spit (or GT6), the simple ideas to take away are; an extra crossmember at the rear (and probably at the front if you've got space) will help quite a bit, and also, if you can find a way to extend the outriggers to the sills (below or above the floors) and join the two structures together proper (welding!!) then you are likely to see another big gain. The Spit sills are surely much stronger that that feeble U section siderail on the Herald/Vitesse.... As regards FEA and rigs.... the rig pictured in that article is actually pretty simple and could be mocked up in a garage pretty cheaply and easily. To get meaningful results from FEA you would need to do this anyway to get starting point data - unless you can persuade Ian or his student to lend you theirs. Probably worth speaking to Ian about it anyway - I have his email somewhere I think. Cheers Nick Edit: Typing too slow.... someone with FEA access already found (they probably should have kept quiet ;D). Board dead...... I don't think so Link to comment Share on other sites More sharing options...
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