20 replies to this topic

[MalcolmB]

I'm an electric car nut who loves minis. I'm half way through converting one mini to electric drive (build thread in Other engine conversions), but already planning my next one. I'm hoping someone can help with a bit of advice. To get drive from the motor to the wheels I'm thinking of mounting a suitable rear diff in the front subframe and driving this via heavy-duty toothed belt from a motor mounted above the diff. The idea is to keep the drive as clean and as maintenance free as possible, so that rules out a chain drive diff.

So does anyone know of a compact rear diff that will fit easily in the front of a mini without fouling the subframe? I know Sierra diffs are a popular choice for kitcars, but does anyone know if one will fit or if there are any other alternatives that are readily available?

Cheers, Malcolm

[Gulfclubby]

All I know is that Fiat Panda 4x4 have a rather small rear axle assembly while being quite popular. I have however no idea whether that would be of any use to you.

[andy pandy]

motor bike powered diff as used on some kit cars etc but change sprocket for belt drive???

[bmcecosse]

Perhaps the final drive unit from a Spitfire/Herald - which will have flanges to which you can fit the drive shafts - somehow!
Can you point me to your electric Mini thread please ?

[tvrdave]

I don't think it matters to a huge extent on the size of the diff, to a reasonable degree, as long as you use inner and outer cv joints, they will allow the shafts to be out of perfect alignment with the wheels but still drive them ok. The only major hurdle i see is that by using an out of line setup you will use slightly more power to drive the car. But basically i would imagine that any small independent rear suspension type diff should be useable.


Dave

[MalcolmB]

Andy: Sorry, I didn't give the full picture. Another reason for wanting to use a rear diff is that I'd also like to have the option of using two small motors that could be placed low in the subframe, either side of the diff and each driving the diff via belts. This would free up all the space above the diff for batteries.

Gulf: Thanks, I'll take a look at the Panda diff.

BMC: Is the Spitfire/Herald diff still widely available?

[=Dooley]

Honda crv rear diff is a lovely little unit ideal I reckon!!

[MalcolmB]

I don't think it matters to a huge extent on the size of the diff, to a reasonable degree

True, but if there's one that fits without loss of efficiency I'd prefer to use it, as every percentage gain means a bit more range. I also need enough clearance at the front of the subframe to fit a wide (50-60 mm ) belt pulley.

Current project (soon to be updated) is here: http://www.theminifo...howtopic=111265

[ANON]

have a look at the freelander diff

[dklawson]

BMC: Is the Spitfire/Herald diff still widely available?

Like most TR parts, there are lots of used items out there and there are a few different drive ratios available. I don't ever remember seeing someone selling new Spitfires diff units.

The trick for any of these options will be adapting/making driveshafts for the differential.

[Ethel]

Drive a wheel off each motor and do away with the diff?

[dklawson]

Drive a wheel off each motor and do away with the diff?

Sounds interesting and complicated... sort of like steering a tank or bulldozer? Wouldn't you have to vary the speed of each wheel independently as you turn? If not, you would be dragging a tire.

[Gulfclubby]

I've seen that done somewhere though. Some guy made exactly that. Try a Youtube search.

[MalcolmB]

I've seen that done somewhere though. Some guy made exactly that.

That was probably me. It works well on the bench, but I've not tried it on the road yet. For the next version I want something that's easier to fabricate using inexpensive off-the-shelf bits. My mission is to find the simplest, cleanest, cheapest and most reliable way to convert a mini.

[Wil_h]

There must be lots of options. Here are some that spring to mind:

- Mazda MX5 - lots about and some specialist breakers
- Subaru Justy - a bit rare, but small
- Any BMW - not sure of size though - Z3 might be a good one

I think I'd be on ebay looking for options then asking the sellers to measure them.