58 replies to this topic

[miniblade81]

r1 mini i agree totally i lost count of how many time i had to start fresh because of drive issues not trying to put your project down darkcat before you have started i really wish you the best of luck keep posting

[darkcat]

Thanks guys - Interesting stuff David!

Miniblade - yes i want it to look as stock as possible, there may be a bit of bulkhead alteration for clearance but the front end should stay standard otherwise - keeping the inner wheel arches too but again may have to recess the passenger side for one of the heads.

David - I think you have mis-understood what i was trying to do - I started mocking the subframe and engine up yesterday (i bought a complete subframe/wishbones/hubs/shafts etc) the driveshafts come into the engine bay close to the back - there is no way to get the engine behind them, as there is about 2" of space!
Having measured up inside the front of the engine bay, I see that after the subframe i have about another 2" to work with after the front of the subframe itself. Having removed the front part of the subframe (which will be replaced later with a box-section custom part once i know what needs to go where) The clutch housing is a pain, i may need to cut out part of the front panel of the car to allow it to stick out a bit, but this should be hidden by the grill.

Height-wise its all looking ok (will need a custom air box) - i have the subframe mounted on a jig that i built to the standard ride-height. The engine's sump is below this, by the same amount as the standard block, this looks like i will get a good inch space from the top of the block to the bonnet.

This leaves me about 4" to work with from the back of the engine to the centre-line of the driveshafts.
If I need more space to work with, I MAY be able to remove the "generator" (alternator) from the back of the engine, (although i haven't tried this yet, so not sure if thats going to be possible) and drive an external alternator from something.

The diff (which im waiting on) should fit into this gap, I may need to make a hole in the bulkhead for the input shaft...

I'll get some photos up tonight

ONWARDS!

Edited by darkcat, 24 September 2012 - 07:58 AM.

[R1mini]

I never heard of a diff being anywhere near that small, but it will be interesting to see some pictures

Cheers
David

[darkcat]

Thats why i was looking at mounting the diff backwards - the cozzy one is quite small too.

Work in progress anyway...!

[darkcat]

well its VERY tight:



engine needs to be offset to the left it seems...

Edited by darkcat, 25 September 2012 - 06:45 PM.

[miniblade81]

would of been a good idea to put a bar in the front of subframe before cutting as frame flexes. gonna be interesting how you will pick up the mounting i dont think you will get that in roundnose if you have had to cut front of frame if you braced front you could get a bit more room at back of frame i take it your going direct diff no chain or cogs

[darkcat]

there was no way i could have braced the frame: where would that go??!!, as i said i intend to put a front brace back in once the configuration is finalised, and before starting the mounting frame build. its only to clear the clutch housing, the block fits nicely under the bonnet.

yes it flexes but i measured the gap + other dimensions before cutting.

It'll fit but i will have to have the clutch housing poking out of the front a bit...! I suppose i could go down the fibreglass clubman front route... but i just spent a load on the grill and lights

If you can name a diff that will fit in that gap without driving it from behind via a shaft, i'll buy you many pints!

Edited by darkcat, 25 September 2012 - 08:11 PM.

[miniblade81]

as drive gos im a little worried about that like you seid it was offset more weight is on one side one thing i would try is swaping shafts over if you intend on using mini shafts or even using two long mini shafts but that will reduce size for diff but id also look at maybe lower engine to allow the diff to fit more in exsaust possition and if more room is required take bit out of subframe and then you are gonna have to mount diff to frame somehow

[darkcat]

oh i had no intention of using the stock shafts - its highly unlikely id ever get a diff with the correct splines/output size to fit the pot joints - that and the length will need changing - the idea is not to worry about that for now, once i get an appropriate diff in position, i can splice new ends onto the original shafts (i have a local engineering company that do this often, and without breakages)

The engine is as low as it can go - the sump is 2" below the subframe.

infact lowering it would make it worse, because the alternator housing would then be completely in the way.

Yes i will need to cut out part of the rear of the subframe in order to mount the diff, and 99% i'll need to make a recess in the bulkhead too.

the big question is what diff to use - i have an MX5 diff which Might do the job, but i have to extract it from its subframe first.

once i have the config sorted i can build a combined engine/diff cradle from steel.

[CraigieB]

crack on son, want to see it finished

[darkcat]

me too!!

but nothing is going to happen until i get hold of a diff...

Why do i suddenly only have 25 forum posts showing?? im sure i had over 200 last month??

[darkcat]

Ok so having done some research into small diffs, it is looking very likely that an ATV (Quad) diff will do the job and fit.
Something along the lines of the Yamaha Grizzly - they run independent suspension, and are designed to take punishment, and even better they have diff-lock

for example:

[darkcat]

Righty then!
We have progress.

Having tracked down a suitably small but rugged diff, and a pair of driveshafts, i decided i'd mock up the positioning:

The only down-side with this diff is that its straight-cut, so will probably be a bit noisy. but to be honest over the chain and engine.... well you know!



and in-situe:



Monica watching on.....





So the plan is to attach a sprocket to the end of the diff input shaft, and drive it via chain from the gearbox output
The diff is a 3.5:1 ratio, which is higher than the 2.4:1 of the original rear sprocket on the bike - therefore gearing this for acceleration as opposed to top speed... i honestly dont want or need to go over 90 in a mini!!! let alone 180!!!!!!!

Edited by darkcat, 09 October 2012 - 06:35 PM.

[Tupers]

That's a really really really cool idea, I hope it works out as planned.

[R1mini]

If you could see the lancia diff pictures you would see the same idea, but using a bmw car differential

I was under the impression, wrongly probably that most ATV's don't have differentials just a bevel drive, ie a spool type drive?

Cheers
David