Right off 325 BMW

[snapper]

Just followed a 325 BMW on the back of a tow truck to a yard after it had been stuck in a ditch on a straight bit of road by Chav-U-like, the reg was covered but it looked like a tidy 2 door probably around the P reg.
It wont be released until the insuranve has been dealt with but its a definate insurance right off.
Have i just found the ideal donor for my roadster project?
Do i use the whole powertrain and front hubs or is it a mix off sierra as well?

[Chris Gibbs]

I think you could do either, I haven't done any detail work yet but several people are heading down this route.

The easiest way would be to use the engine and box with Sierra front uprights and rear axle.

The BMW front uprights could be used in this sort of way:-

http://i126.photobucket.com/albums/p112/chrisg222/bmwfrontupright4.jpg
The fabrication replaces the standard strut.

At the rear I think that the easiest way to use the rear axle is to place the differential in place and make plates to suit. I don't think the suspension is suitable (none of the links are parralel to the axle line or the centreline of the car and I think the best way to proceed would be to cut the bearing carrier from the trailing arm and weld this to an upright similar to the Sierra based Roadster.

I'm hoping that between us we can sort out a very good set-up ;)

Cheers

Chris

[rmccomiskie]

I'm particularly interested in hubs from E30 or E36.

Bob.

[Chris_]

Wont a 6 pot be a little tight in the bay? Not to mention heavy. (117kgs)

Especially with it being quite wide due to the heave cant.

Oh and a problem with the diff could come about with the single 'ear' like load bearing mount. Will this throw off how the loads are transmitted through the chassis?

If you find ways around all the problems i would love to know as rusty E30's are sooo cheap now. And the mechanicals are easy to work with as well as being reliable.

Chris:)

[rmccomiskie]

Oops! I wasn't clear. I'm considering the 4 cylinder M42 engine and gearbox from a 318i. I've seen a couple of such builds on the Web.

Drawings of front upright adapters are encouraging. I'd like to use a single donor for most parts but I haven't seen how the diff mounts. Will have to evaluate the chassis loads if it's a strange mount. Rear uprights are still a question too. The BMW rears carriers don't look too promising.

[Chris_]

Ahh, M42 is a much simpler proposition. Profile gasket should be checked out while its out though and might as well do the cam chain tensioner. Cant help much more though, i'm a six pot boy :o

E30 diffs are the same across the range with regard to mounting.
They come as either small or medium case. Bigger obviously stronger and fitted to the larger engined cars.

Favourable ratios or LSD (for a 1000kg BM) are getting a bit pricey now up around £250-350 but i dont know what sort of ratio you need in a roadster (not started building yet)

Mount with four large bolts on top through the rear beam, and a large bushe mounted 'ear' to one side. (this can be replaced with a Z3 bush for stronger mounting)

http://i185.photobucket.com/albums/x168/Chris_51_/25042009007.jpg

Cheers
Chris

[HandyAndy]

sorry to invade the thread but
HAPPY BIRTHDAY Chris.
hope you,ve had a good un.

andy

[Chris_]

Ahh, thank you :D

Might have to shrink that piccy. It's a bit bigger than i expected.

Chris

[Chris_]

Ooh, another piccy of E30 rear ends.

http://i251.photobucket.com/albums/gg307/leightoncars/IMGP0958.jpg

Chris

[rmccomiskie]

Mount with four large bolts on top through the rear beam, and a large bushe mounted 'ear' to one side. (this can be replaced with a Z3 bush for stronger mounting)

Hmm. What is the purpose of the 'ear' mount? Does that isolate the torque reaction? Does the diff hang on the ear or could an arm be attached from the ear to the chassis?

Thanks for the pics.

Bob.

[Chris_]

Couldn't tell you in any major technical detail. but.

The four bolts hold it to the rear beam, the rear beam attaches to the body with some quite sturdy bushes, one at each end.
Although these are strong i think they would be wear out a lot quicker if it wasn't for the 'ear' which i have always just presumed is the main torque bearing structure. But actually looking at it a little closer, i reckon you might get away with just mounting it with the four bolts.
They are spread across a decent length, and are at two different seperation distances. I reckon it could take the loading ok.

Need someone clever to look at it i reckon.

Chris

[Chris_]

Mind you, (thinking again, always bad for me) when they run proper power in E30's the bodyshell where the rear cover bush (the 'ear') mounts does have a tendancy to rip away so it must take some fairly significant forces.

Hows about an E36 diff (not compact) these have a pair of 'ears' and are considered to be stronger. As well as more symetrical.

Chris

[Chris_]

Right i've been musing over this at work today, did some (very very) rough drawings and measureings.

I reckon, but dont quote me on it, The Diff is subjected to torque loadings on two axis - The longitudinal twist from the prop shaft/gearbox/engine. And the latitudinal twist from the road wheel friction (equal and opposite Blah de blah)
So the four main mount bolts hold the diff solidly to the rear beam which then opposes the torque of the prop shaft through the entire width of the beam and the butch mounts at each end (decent leverage, lower force)
The big ear at the back is a just a stabilising link. Friction from the tyre-road interface will try to oppose the driveing torque and force the rear of the diff off of it's centre line. It it didn't have the 'ear' it would be working on a lever about 18 inches to try and break the beam bushes. So they've thrown in this rear stabiliser.

So, Cut the ear off, solid mount the diff from two transverse box sections of of a pair off diaginal longitudinal box sections, job done.

I think they are M12's so get 8.8's and it 'should' be strong enough with the weight of a roadster ;)

Cheers
Chris

[RAYLEE29]

Hi, looking at your picture the set up is v similar to the sierra and the ear mount is there to stop the diff/beam moving up/down.
if you were to fit it in the roadster chassis you can mount it using the four front bolts and do away with the rear mount as you will be mounting solidly direct to chassis not via a rubber mounted beam
Ray:)

[GraemeWebb]

See my flicker pics for what I am doing with my 4 cyl bmw build. Will post some pics of my front upright conversion soon.