Sprint 6C build up - Page 9 - Alfa Romeo Forum
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Re: Sprint 6C build up

Ive lowered my 33 a while back. Got the springs from justsuds. The springs are quite a bit shorter but it didn't have the impact i was hoping for when i dropped it back onto its wheels. Guess my original springs were completely shot but the reduced length may be enough in this situation.

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Re: Sprint 6C build up

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Originally Posted by kevjtd View Post
what about lowering springs for a 33? they must be available somewhere? think you may get dificulties getting it low enough without the weight of the engine to compress the springs?
sure someone will come up with a solution
Make the front into a boot and stick a few bags of sand in there
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Re: Sprint 6C build up

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Make the front into a boot and stick a few bags of sand in there








 
 
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Re: Sprint 6C build up

what about springs from something like a fiat x1/9? something designed with a rear engine?
wouldn't ordinary sud/sprint/33 springs be too stiff without much weight on them?
 
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Re: Sprint 6C build up

Demon Tweeks do a range of generic springs, if you have an ideae of length and stiffness then they may have some off the shelf.

I have some Sud springs that came off a racer, lowered and about 175lb, so while not stiff enough for racing, maybe too stiff for the road?
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Re: Sprint 6C build up

In fact, I have some lowered 33 front springs, post the lenght and coil thickness of your standard springs and I'll compare to the 33 set and see of they might help you.
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Re: Sprint 6C build up

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....... Has anybody else done a similar job?

these guys have.. Giocattolo. I'm sure a search around the web on this car will reveal how they sorted the front end.
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Re: Sprint 6C build up

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Originally Posted by veesix75 View Post
In fact, I have some lowered 33 front springs, post the lenght and coil thickness of your standard springs and I'll compare to the 33 set and see of they might help you.
Hi Tim
The Springs are still on the struts so I cannot say what the free length is, (At least 8.5") - (The Haynes manual says the free length is 11.5") but there are 4 coils and the wire dia is 0.55" - According to the Alfa BB thread the rate of the Sprint front spring was 130lb/in so the shorter stiffer 33 springs may be suitable...
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Re: Sprint 6C build up

Hi Sixnut - if you are keeping the front struts, cutting coils off the spring to lower the stance will increase the spring stiffness, so the front will be lower, but you'll be skipping all over the place. You definately need softer springs, which should compress more and lower the stance that way.

Is there enough room under the bonnet to raise the strut top mounts? That would lower the ride height without changing the spring rate. You'd still need softer springs though, you've taken out an engine and transmission + driveshafts and you are putting only a fuel tank in their place. What would that equate to? A 300 lb reduction? Split between the two front wheels 150 lb per wheel, same as the spring rate, so at least 1" higher at the front.

To do the job properly you need to know the corner weights, and measure the unsprung weight of the strut/wheel combination, set a target suspension natural frequency (cruiser/sporty/full race/GFX) and work out the resulting spring rate. As the natural frequency at the front needs to be lower than the rear to stop front/rear pitching effects, for your mid engined machine the front spring rates will need to be quite a lot softer than the rears (which are 164 struts, what is the spring rate?). You won't find any Alfa springs at rates of around 100-120 lb/in (which I think you would need), I would check out manufacturers who can wind a custom spring, or as Kev suggests, maybe the front struts from an X1-9 would do the job (they'll be shorter too!).

Conversely, now that most of the cars weight is on the back wheels, you might find that the 164 springs are too soft. There again, the Sprint shell is probably lighter than the 164 bodywork, but my point is you will need some fine tuning or the car will be a nightmare to drive (and I've got three complete sets of redundant springs in the garage to prove it!)

Green Machine has a custom fabricated alloy fuel tank. Its TIG welded and had a number of pinhole leaks which had to be painstakingly rectified (not by me, my welding is of the "pidgeon poo" variety ) with the tank removed from the car and drained out. Fuel tanks can be fabricated out of steel as well, which might be easier to do.

With plenty of space under the bonnet, I would go for a proprietary racing tank, one of those alloy ones or if you are feeling flush, an ATL fuel cell.

Still making excellent progress. Nice beading on your engine bulkhead by the way

Lauren

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Re: Sprint 6C build up

why not get a 2 1/4" universal coil over kit, it will save a lot of messing around and give you the benefit of playing with lengths and rates, as long as your struts have inserts its just a case of cutting of the top lip and spring seat..heres an old pic of my strut.
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File Type: jpg sud13.jpg (64.3 KB, 21 views)
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Re: Sprint 6C build up

Well LOTS of food for thought with very useful information from Kev, Lauren and Alfa 302.
Trying to pull lots of it together, the standard springs seem to have a low spring rate - 115lb/in (?) but are compressed or preloaded in the suspension strut by about 3" so with the weight of the engine etc the spring only compresses an extra inch or so to give the normal ride height.
So if I do remove a coil the preload will be less, the Spring rate about 160Lb/In and the ride height lower. But the front may well skip about. The rear is also effectively stiffer and the springs have less weight on them as the Sprint shell is much lighter - but the other factor is that the engine is in fact more Mid mounted -- I think it will have to be tried then Ill find the corner weights etc and retune the suspension in the light of experience - Also I have little money for nice "exotica"
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Re: Sprint 6C build up

Try this site Professional Motorsport Parts, Spares & Rally Equipment from Rally Design they have roller bearing top mounts 2 for £119 and a universal conversion kit 2 for £63 add a pr of springs for about £30 and your done, or try surfing the net for a better deal. With what you have done already it would be an easy conversion and no guessing work involved. Heating and cutting springs is not something I would do as you may find one spring is harder than the other...what ever you decide to do, best of luck
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Re: Sprint 6C build up

I'll definately second that!

The universal strut option looks like a good bet, but the range of spring rates/lengths needs to be sufficient to cover Sixnut's extreme case of an Alfa Sprint with no engine or transmission (not a common request I suspect ).

I tend to agree with your appraisal Sixnut - get the thing on the road and see how it feels, then change spring rates as required. With a bit of luck you'll find the rear is fine (doesn't wallow, but at the same time isn't dancing all over the road) and all you need to do is adjust the front spring rate/length.

Unfortunately Green Machine started off with 250 lb springs all round, which made it too soft at the back and too hard at the front. Plus the ride height was too low because they were all too short. Next iteration (again pure guesswork) put longer 300 lb springs all round. Even worse.

When I finally got the corner weights measured, I found that my suspension natural freuqencies were at F1 levels at the front (OK, maybe F3000, but still waaaaay too high), while the back was OK, but perhaps on the softer side of "sporting".

So I had to do a third iteration based on a more scientific analysis of the suspension, but you should be able to do the same job in two bites, and hopefully you will only have to spend money once!

By the way, my spring rates are higher than the strut rates because I am using wishbones all round and the spring/damper units are (a) inclined relative to the vertical and (b) not acting directly on the wheel axis so there is a force multiplication factor involved. However, I recently analysed a colleagues Nova (kit like mine, only with the original VW running gear) and his direct acting coil-over replacements for the Beetle front beam came out at 110 lb/in per wheel. No water radiator up front in this case, but dual batteries and a heavy fibreglass layup makes me suspect that your front spring rates aren't going to be much higher than 120 lb/in...

Its going to be a riot when its done

Lauren
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Re: Sprint 6C build up

had a look for springs on the above site, they have 100 lb rate at 8" for 14.90, so guessing(which i do not like doing) if they compress 1-2 inchs they could be the right height just need to check the rate..the front kit is £42 not £63 as i said before that was for the rear kit so even better value..any chance of it being ready for march/april 09?
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Re: Sprint 6C build up

Lauren - your technical analysis and appreciation of the problem is spot-on! There are so many variables that a trial and error approach will have to be adopted.
My bulkhead bending was complicated by the fluting on the bonnet and reinforcing struts behind - but it will look better soon.
This also means that Alfa 302's query about "finish" date could be about right, in as much as it could be up and running, with all systems in place by Easter next year - but still needing cosmetic bodywork tidying up - which will take ages!! (And thanks for the "Rally Design" link, there are all sorts of useful bits - once I get some money!!)
However I will have to swap Sprints soon, to assemble, and sell off the 1.5 Sprint.
I am, at present, investigating the GTV (1977) fuel tank as a possible solution to that problem ....
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Re: Sprint 6C build up

Further progress as I now have a GTV fuel tank to try - and it seems to fill the engine bay very nicely. ....so here are three more pics showing the 164 radiator in place with the fuel tank just positioned roughly behind. Obviously there are mounting brackets and lots of pipes to get made and connected.
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File Type: jpg 6c build up 7 radiator and fuel tank 001.jpg (128.2 KB, 34 views)
File Type: jpg 6c build up 7 radiator and fuel tank 002.jpg (139.1 KB, 38 views)
File Type: jpg 6c build up 7 radiator and fuel tank 003.jpg (142.8 KB, 33 views)
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Re: Sprint 6C build up

looks like you have your favoured alfa tank then , great result
have you thought about a location for the tank filler or will it be a case of opening the bonnet and just fill it up , certainly would be the easiest way but a fill up flap in the front wing would be a nice touch

making good progress mate, nearly all the problems solved , or thought about anyway
 
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Re: Sprint 6C build up

Working on the fuel tank and its now turned through 90 degrees with the filler neck against the nearside inner wing. Two mounting brackets made and a brace across the front to fabricate next.
Kev
I thought about putting the Sprint filler flap housing on the front wing, as I have cut it out from the rear wing, but it would make the wing removal more involved and mean cutting through the inner wheel arch - so I think I will just need to open the bonnet for refuelling...... Easier, and keeps the clean lines of the wing.
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Re: Sprint 6C build up

That would look pretty cool opening the bonnet at the petrol station to fill up
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Re: Sprint 6C build up

Hi Alfasixnut,
Was the GTV fuel injected ? Just worried about swirlpots high pressure fuelpumps returns etc. missing making life difficult.
And please tell me the brakes are getting a bit bigger , running into the back of someone doesn't bear thinking about.
Keep up the good work.
KR James
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Re: Sprint 6C build up

Not too much to report - here is the final position of the fuel tank - which has had a quick clean up and spray. The rear bracket bolts through the double thickness bulkhead. I am working on a "T" shaped strut to go across the front and up the centre to support the tank and provide more structural strength. Having the tank on the nearside will help with the weight distribution and also allow the water pipes to the radiator to run in the tunnel and up alongside the tank to the radiator inlet/outlets, which can be seen on the drivers side.
James and Nick - yes the braking will be modified as I will be using the much bigger discs from the 164 at the rear. The front system will remain as standard, as the fronts may lock up with less weight on them. However it is not a track or race car, so the brakes will not get extreme hammering - I'm a gentle driver!
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Re: Sprint 6C build up

Don't want to sound negative here but the position and type of tank you're using makes it very vulnerable in the event of a front end collision

Even a small impact will will split that tank open with potentially devastating consequences. You've got electric cooling fans immediately in front of the tank. A spark from them after an impact could ignite any fuel vapour and set the whole thing ablaze.

A more narrow upright tank positioned against the bulkhead would be an improvement but a protected fuel cell is really the best solution.
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Re: Sprint 6C build up

I would agree that a fuel cell is probably the best solution, but many fuel tanks overhang the rear axle (the 'Sud is an exception I know) which makes them no safer in a rear end shunt - Sixnut is retaining the 'Sud front subframe and if he puts some diagonal bracing bars up to the main bulkhead that should create a triangulated cage around the tank.

With a mid-engine configuration there is a lot less front weight bias, even under heavy braking, so the standard (outboard, presumably) front discs should suffice, although a brake balance bar would be a good idea. Green Machine has a 46:54 weight distribution (46% on the front axle), and my brake bias bar is would 6 turns off the front - still locks the front wheels under spirited braking

Looking good Sixnut!

Lauren
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Re: Sprint 6C build up

When the 6C finally hits the road it may well be that the DOT will insist on an SVA (Single vehicle approval) test as it has been so extensively modified.

Having already done one of these after building a kit car I can tell you that it is highly unlikely that the car will pass with this type and position of fuel tank.

Front end collisions are at least ten fold more common place than rear end collisions. Rear end collisions rarely involve hitting solid stationary objects so the energy on impact can be less. Incidentally, virtually all "modern" car have their fuel tanks forward of the rear axle and there's a spare wheel well behind it to absorb rear impact. Also most fuel tanks are now made of deformable plastic to stop them splitting open.

I think it's a fantastic project that Alfasixnut has taken on and I've been following his progress with great interest but this particular aspect of the build is an absolute no brainer in my mind.
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Re: Sprint 6C build up

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When the 6C finally hits the road it may well be that the DOT will insist on an SVA (Single vehicle approval) test as it has been so extensively modified.

Having already done one of these after building a kit car I can tell you that it is highly unlikely that the car will pass with this type and position of fuel tank.

:
Depends what you tell them...
An MOT and a change in engine number and size might be the way forward........
Agree that a cell might be a good way to go though , they often come with nice fillers etc. which would give a fantastic feature on opening up the bonnet.
KR James
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