1972 Mini Cooper E.

28275 Views 44 Replies 13 Participants Last post by onegreenev, Aug 2, 2014

Jaesin

Discussion Starter · Oct 31, 2011

First of all, I would like to let you all know that all of your hard work has inspired me to start my conversion a year earlier than I initially planned.

My car is a 1972 Mini. I have owned it since 2005. The engine has smoked since I got it and I've been dreaming for years now about ways to get away from this nasty old oil puffing raga-motor.

For those of you who've had any experience with this car, you know that space is the main issue with it. The car was very well designed and wasted no space at all.

The Transmission:

Most folks think the stock trany isn't of much use. I mostly agree with this. It sits in the oil pan of the ICE. Basically, it is the oil pan. It also sits in kind of an awkward position. It's right in the middle. there is a few inches in front of it, and there is a few behind it but not really enough space to put any batteries or the controller.

I'm using it anyway:
The thing is, I am converting this car in two stages. I want to get rid of my other car so I am converting this car now. That way, I can drive it while I work on the car's more permanent AC system. That means that quick and dirty (AKA, fast and cheap) DC system for now.

Slap Chop:
A very nice gentleman I met at the EVVCON sold me a Curtis DC Controller with a contractor, heat sink and two fans already assembled. On top of that, he offered it to me at a very good price. Thanks Einar!

Coils and armatures:
I picked a D&D 6.7" motor (that's right, just one). It puts out a bit more torque @ 1600 RPM's than the stock ICE peak torque of 52 lb-ft @ 2700. The D&D would put out 80 ft-lbs @ 1600 RPM if I could give it another 83 amps.

Connecting Bits:
I am going to use a chain drive and nix the clutch. The output shaft of the motor and the input shaft of the gearbox were at a one-to-one ration so I am going to gear up the motor a bit. I want to have some usable torque at 65 MPH and I figure most people don't really use 1st gear. I'll aim for a about a 2-1 chain drive (calculations pending).

12V+:
I am currently working on the DC-DC Converter. I bought some 3.3V Vicor modules that I will wire the output in series for a max of around 20A @ 13.5VDC.

Some Pictures.

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MalcolmB

· #3 · Oct 31, 2011

Hi Jaesin. Sounds like a good plan. I'll be watching this. Will you fabricate a new end plate for the gearbox or just modify the existing one? Last time I looked at the gearbox it seemed there might be enough room to fit in a chain drive if you used fairly small sprockets.

Those DC converters look familiar

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MalcolmB

· #16 · Nov 2, 2011

I agree with Duncan about the coil setup and brakes. I've looked at doing this at the front and rear (with a beam subframe). The consensus on the UK mini forum is that the standard rubber doughnuts and brake setup are very good and you can waste a lot of time and money trying to improve on them. The most cost-effective way to improve handling is to fit new doughnuts and dampers, as the rubber doughnuts last about seven years before stiffening up. Since you'll be changing the weight distribution it's also worth fitting hi-los – replacement suspension cones that let you adjust the ride height front and back.

As for brakes, the front drums are actually pretty good if well maintained. The 8.4" discs are a significant improvement. It's not worth doing much at the back, as the performance of the existing drums if well maintained is more than you can use – it's limited by the proportioning valve, as Duncan said.

I'm fairly sure you'll also need the later drive shafts to mate with the pot (CV) joints on your replacement box.

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MalcolmB

· #25 · Apr 3, 2012 (Edited)

Hi Jaesin. Yes, the space in the rear subframe is just about right for 30 x 100 Ah cells. Those prismatic cells make packaging so much easier than any alternative, especially in a Mini. I've been struggling to find a way to fit a relatively small pack of cylindrical cells in the boot, and finally admitted defeat, so they're going in the rear seat space instead. The cells would have been so close to the boot lid that the slightest nudge would have meant disaster. The improved weight distribution has to be an advantage. I don't have any experience racing Minis, but would expect that it will reduce understeer without causing any unwanted tail happiness.

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MalcolmB

· #27 · Jul 11, 2012

Great to see this Jaesin! I was very close to trying this myself, so it's good to see someone else have a go. The aluminium mount looks nice and solid and the Union Jack pattern on the end plate is a nice touch.

Did you end up going with the 2:1 sprocket ratio? I can see the top sprocket's a 22t, so 11t on the bottom?

Did you have a new input shaft made or just modify the existing one?

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MalcolmB

· #30 · Jul 12, 2012

Thanks for the info Jaesin. I'll be interested to hear how the gearing works out. 2.2:1 does sound a bit high, but on the other hand most people seem to find that the stock first gear ratio is way too low to be useful.

I did a bit of reading about chain drives for my own conversion and one of the recommendations is to avoid using low tooth counts, as it leads to accelerated wear. I think a lot of the documentation is over-conservative though. If you look at most motorcycle drives they seem to be outside the recommended envelope for long life. You've also got the advantage of a sealed oil bath, which makes a big difference.

I went to the opposite extreme and used 3/8" duplex chain, which lets you use a higher tooth count but isn't as strong as 5/8". There's only one way to find out if it's strong enough...

That's useful feedback about chain versus belt from Kleenspeed. I've heard a couple of other people say that belt is noisy and runs hot, so I guess I'll stick with chain too.

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MalcolmB

· #41 · Aug 2, 2012

Well done Jaesin! It looks and sounds just right. I'm glad you went to the trouble of milling a proper keyway in the shaft.

It's a shame that space is so tight inside the transmission end plate, but then it wouldn't be a mini without all the space constraints to deal with...

I'd just finished rebuilding my subframe and motors, snugged all the bolts up, installed the reversing contactors, made and fitted the main power cables, then did a bench test and realised I'd forgotten to fit a couple of spacers on the stub drive shafts, so the driven sprockets are free to slide up and down the shafts... Doh!

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1972 Mini Cooper E.

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