Anyone know how strong the Spire GTr chassis is in terms of what Hp/lb ft in can handle, or a ball park figure? I'm thinking of doing something silly with one and need to know the chassis will be up to it, either as standard of with some additional bracing.

[Edited on 16/10/06 by DIY Si]
Rescued attachment development1.jpg

looks like it needs a bucket load of triangulating to me. sorry that's not much help but with any engine be it big hp or not that picture could do with diagonals added in most areas imho.

Ned.

hard to guess without seeing the back end, where the magic happens. As ned says the front look a little barren, but that would mostly affect handling rather than what power would make it crumple.

I do like the high sides with the X in it though

I'm pretty confident I could add a fair amount to the chassis in terms of triangulation/extra bracing, possibly enough to deal with what I have in mind. I'm thinking of doing something truly a bit silly (or so swmbo thinks) with it. Somehting 400+ on both important numbers! I don't think I could sensibly make/design a chassis from scratch to cope with all that. Unless soemone has a suitable chassis plan up their sleave?

assuming that the spire chassis is jigged up well to start with, and you dont need to remove many tubes, its probably a good start. Adding bracing is both fun and easy! lol.

what engine?!

It's something a little spicy, yet totally in standard form. I It's a 4.2 supercharged V8 from the jag XKR.

It has 408 lb ft as stock and 400 bhp!
Only bugger so far is sourcing a transaxle capable of delivering all of that, but I think I may have that covered. Just. Or, as long as i don't tune the engine, something I find very hard to resist.

[Edited on 16/10/06 by DIY Si]

How about binning the rice burner, You'll get reverse then aswell

ATB Dan. See you tomorrow

I'll be selling/am selling the Indy to help fund such a project. If I pick the right transaxle I could have 6 gears and backwards! Or just 4 forward gears and backwards if I have to use a strong Porsche 'box. I won't really be able to push this one around so easiyl, as it'll probably weigh in at 600-650 kgs and have full body work. It should still give ~ 670 bhp/tonne!

That should be enough top scare the Cr*p out of you

ATB Dan.

Hopefully!
Oh, and I get a better sound track. But only 6.5-7 krpm.

quote:

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Originally posted by DIY Si
I'm pretty confident I could add a fair amount to the chassis in terms of triangulation/extra bracing, possibly enough to deal with what I have in mind. I'm thinking of doing something truly a bit silly (or so swmbo thinks) with it. Somehting 400+ on both important numbers! I don't think I could sensibly make/design a chassis from scratch to cope with all that. Unless soemone has a suitable chassis plan up their sleave?

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quote:

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Originally posted by DIY Si
I'll be selling/am selling the Indy to help fund such a project. If I pick the right transaxle I could have 6 gears and backwards! Or just 4 forward gears and backwards if I have to use a strong Porsche 'box. I won't really be able to push this one around so easiyl, as it'll probably weigh in at 600-650 kgs and have full body work. It should still give ~ 670 bhp/tonne!

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It's not the weight that's the problem so much, it's that the roll bar will be relatively inboard when compared with many. Unless I fit a really massive roll cage, rather than a just massive one which I intend to use. The sills/side pods are best part of a foot wide and leaning over and pushing could be a pain. And it'll have backwards anyway, so I might as well take advantage of having it!

Porsche box will be no probs.

My mate at ultima uses them with 725 hp and 600+ lbft of torque, and they haven't broken in 15,000 miles behind that!

That one is a 5 speed G50, but the 6 speed getrag box is pretty tough too, fine for 500hp

Do they use the G50, or the stronger (or so I've been told) G50-50 series of boxes? Given that you know a bloke (the MD?) at Ultima, do you know if they've got any spare?
I didn't realise that the GD chassis and panel set is £4,600! For £3,000 I can get the chassis and body and wishbones from Spire, although I may just make some wishbones to use the granada/cortina uprights.


[Edited on 17/10/06 by DIY Si]

I can probably source a box for you (as long as you don't say where you got it from lol! ) but I doubt it will be cheap.

I think they charge £5000 for a brand new 6 speed (off the top of my head)

They get s/h G50's in fairly often so I will enquire for you, guess you will be looking at £1500 to £1800 for a goodun

I will ask about the various boxes bu as far as I know they either use the G50 or the 6 speed getrag. The G50 is no longer available new so all new reg cars tend to have the 6 speed, which I think is not quite as strong, but then still takes 500hp and 500lbft with no trouble.

Will ask for you and let you know.

Crikey! That seems a bit more than I was expecting. Having read a fair bit on some of the GT40 sites, they seem to think the audi 016 box is capable of 450+ lbft given a steel plate internally. What's better is you can get an old audi 100 for £200-300! I have to get any and all purchases past the Boss, so if a cheaper option exists, that's prefered.

a lot of the v8 grassers use audi boxes and they seem to hold up ok, was going to suggest that one!

What Audis were the 016 boxes fitted to?

As far as I can tell, the Audi 100 and the 5000, although I'm not sure if that's a european or american model. There are also different gear ratios and final drives to suit various plans too. Not a clue which one is the most suitable though although the 3U version is talked about, but again no idea which model it comes from.

This gives a good guide on gear ratios.
And this gives yet more info/ pics on the subject

[Edited on 17/10/06 by DIY Si]

This is my mock up frame.
torsion test

I measured the torsional rigidity

df canamsa proto side pod

Torsional rigidity without side boxes = 2700 ft/lb/Deg

Torsional rigidity with side boxes = 5700 ft/lb/fl/Deg
[img][/img]

I put a transaxle contribution in your thread in "Engine and Trans"

Cheers

Fred W B


[Edited on 17/10/06 by Fred W B]

Does anybody have contact details for the Spire?

Spire Sports Cars

[Edited on 17/10/06 by Gav]

Fred, how are you going to fit the engine in there? Otherwise looks roughly simialr to what I want to achieve, but I don't feel able to sort all the suspension mounts/placing on my own, as I don't know enough about suspension geo set ups yet.
Will the final chassis look much different from that? Do you intend upping the power/changing the engine in the future, or waht power do you think your chassis could deal with?

[Edited on 17/10/06 by DIY Si]

WRT getting the engine in, the rear top section of the frame bolts on, see more discussion
here

WRT engine power, who knows?

Looking at this list though, with 5700 ftlb/Deg it would seem that it could take quite a lot?

For comparison I list several other chassis figures, obtained from various sources on the internet, particularly contributors to www.locostbuilders.co.uk

Ultima - 3300 ftlb/Deg (coupe) and 2500 ftlb/Deg (spyder)mass 135 kg,
Lotus 23 - 1500 ftlbs/Deg, 45 kg
Lotus 7 replica, "locost book" spec - 1200 ftlbs/Deg, 82 kg
Lotus 7 replica, uprated "cymtriks" spec - 2540 ftlbs/Deg, 78 kg
Lotus Elise - 7350 ftlbs/Deg,
Lamborghini Countach - 1900 fp/degree.
Ferrari 360 spider - 6250 fp/degree.
Lotus Elan: 5,000 - lb-ft/deg
Porsche 959 - 9,500 lbs-ft/deg
Lotus Esprit SE Turbo - 4,300 lbs-ft/deg
GTD Lola T70 replica - 3300 ft/lbs per degree.

Cheers

Fred WB


[Edited on 18/10/06 by Fred W B]

Hi i think Fred must have a fondnes for the birdcage masserati. How ever it dose show just how lacking the mkgt/spire chassis is and would probably be easier to start from a fresh and do a chassis that has all the right triangulation incorporated into the main frame instead of having to add a load of extra to a chassis that was wrong in the first place. Would also mean that mounting the engine/gearbox and ancilaries could be done easier if the chassis was desighned around the parts you have rather than having to compromise at every turn in construction.

cheers matt

I have thought about it matt, but as said I don't want to go through the extensive hassle of building from scratch to only end up with a rubbish suspension set up. Unless someone could measure a well working set up for me, and I can build a jig to work round it perhaps? I'm learnign about suspension stuff as I go, but I know a bit more about basic chassis stuff at the mo.

Sounds like a really interesting project and I can't wait to hear more about it.
You need to decide what dimensions your car is going to be, will you be using the spire body? is that why you are considering their chasis?
I must admit that I have seriously considered doing a spire myself (flogging the R1 Indy I have) and putting either a Ducai 996 or subaru engine in (subaru is current favorite for me)... If I did I would have had the chasis from them and basically made an all new one around the wishbones etc.

Like Fred I have deisgned and made my own chasis for my GTT, I however paid someone to design the geometry around the dimensions I wanted. so there are people out there that can help geometry design and wishbones, if you wanted something similar to an Ultima that would be quite simple to reproduce.

Here's a pic of my chassis which takes a slightly different direction to what Fred did, but basically I have side box sections as well as the central tunnel that sigificantly increase stiffness.
I have done some extra triangulation since this shot but it gives you an idea.




Regarding the porsche box the G50's or the old 930 are the affordable ones to go for.
Don't use the 996 Porsche Getrag box though, its weak and can't be repaired for under £2k even to replace syncros.... to press this point I have a mate who spent £6k on a brand new one from Ultima and in 1500 running in miles it is already broken with only a 450bhp engine. It's not the first one to have gone either.

The modern Audi boxs are a good choice, 6 speed 2wd ones from the diesel A6's can take the power I don't know the model number though.

[Edited on 18/10/07 by gttman]

I don't too much extra triangulation is require except in the front bay and the steering rack mounting !

A few diagonals and some sheet steel or thick alloy would stiffen things up a lot. Key is not to go daft adding diagonals, just stiffen each unbraced square with one diagonal. If you start adding criss-cross diagonals the stiffness doesn't necessarily increase.


The side pods have the potential to add a lot of stiffness.

Main problem I can see is that for that amount of power I would want a longer wheelbase to make it less lethal.

I would also want to make sure it was aerodynamically stable --- a few of the old Group 7 Can-Am cars flipped when the nose lifted at high speed.

[Edited on 18/10/07 by britishtrident]