[MalcolmB]

I've been talking about this for long enough and I've changed my mind about how to do it countless times, but I've finally made a start on my Mini conversion.
I've got to come clean first and say it's not a completely authentic Mini, as it was rebodied some years ago with a glass fibre shell. Otherwise it's a Mini through and through, complete with leaks, ageing 1275 A-series engine and gokart handling.

She's currently buried outside under 12 inches of snow, but I've bought a spare front subframe so that I can get the motors mounted and refurbish the front running gear over winter. I found a couple of Prestolite 7" motors a while back, via an ebay contact. They're rated at 130A continuous at 36V. I've advanced them by eight degrees and plan to run them at around 120V each.

The motors have actually been shortened by around 40mm since I took the photo below. This was done by removing the internal fan, and machining back the alloy "legs" on the drive end. It was the only way I could get the two motors to fit across the subframe and also gave me a decent length of plain shaft to mount the drive sprocket on. I'm not going to worry about whether it's unbalanced the motors yet...
Each of the motors will drive a chain sprocket mounted on the inboard ends of the half shafts, so no gearbox, no diff. I'm busy making up two pairs of bearing carriers that will each support a short shaft with a sprocket on one end and a CV joint on the other. I'll post some photos in a few days when I've got something worth showing.

Now to the first of many daft questions: I want to keep this conversion as simple (and hopefully cheap) as possible. I've been looking at options for providing vacuum and 12V power and the simplest way I can see to do that would be to use the tail shaft on one motor to drive a mechanical vacuum pump, and use the tail shaft on the other to drive a lightweight alternator. The question is, if I have the motors wired in series to a single controller, is the small difference in load on each motor likely to cause any problems?

[major]

Originally Posted by MalcolmB

The question is, if I have the motors wired in series to a single controller, is the small difference in load on each motor likely to cause any problems?

Hi Malc,

I assume they are series motors, identical designs. Then when in series, they will be forced to have the same load; that is current therefore the same torque. So if you take more torque from one motor shaft for accessories than the other, one of your drive wheels will get a little less torque. I don't really have any idea if that would be noticeable to you or not

Which Prestolite motors are those?

major

[MalcolmB]

Originally Posted by major

Which Prestolite motors are those?

I've searched high and low for more information, but no luck. All I have is from the rating plate: Part no. LKAR4002, Class H, 3.6 kW, Class H windings. They have a 33 bar comm. Pretty sure they're series wound. They were Army surplus.

[major]

Originally Posted by MalcolmB

I've searched high and low for more information, but no luck. All I have is from the rating plate: Part no. LKAR4002, Class H, 3.6 kW, Class H windings. They have a 33 bar comm. Pretty sure they're series wound. They were Army surplus.

My experience with Prestolite dates way back. I didn't know they did any "Army" motors and the LKAR prefix is post my time. Also, Prestolite went bankrupt and split apart, and there was also an Asian Prestolite (non-related from what I can tell) and divisions in the UK.

But if they are the 7.2 inch diameter frame with the 33 slot and bar armature (from the old design), they are very good machines. If you can post some photos of the guts, I may be able to tell you more.

major

[MalcolmB]

Yes I've read some of your earlier comments about the Prestolite motors. This one is labelled Ametek-Prestolite, so it would have been after the split, but it looks to me to be similar in construction to the earlier ones I've seen. The stack is shorter though, at around 5 1/2 inches. Here are a couple of photos I posted ages ago in the fork lift motor thread.

[major]

Originally Posted by MalcolmB

Yes I've read some of your earlier comments about the Prestolite motors. This one is labelled Ametek-Prestolite, so it would have been after the split, but it looks to me to be similar in construction to the earlier ones I've seen. The stack is shorter though, at around 5 1/2 inches. Here are a couple of photos I posted ages ago in the fork lift motor thread.

Kool Ametek-Prestolite. I think they ended up with the Prestolite factories and tooling. Then it might just be MGP lamination. Likely a 5" stack. And they look like series field coils. And dual double shunt brushes. About the same brush as a Warp9 or 11 I think you have a couple of keepers

[MalcolmB]

That's good to hear, especially from you Major. One thing that's been nagging me is whether I'll have enough torque for decent bottom end performance. Obviously that depends on the gear ratio, but space is so tight in a Mini that the practical upper limit is about 4.5:1 with a single-stage reduction. These motors produce 10.5 ft lbs of torque at 130A (5 hp at 2500 rpm), which doesn't seem much when you compare it with some of the brutes that others are playing with here.

Looking around at other motors of similar size and rating I've been using a guesstimated figure of 70 ft lbs from each motor at 500A. Does that sound too optimistic?

[Huff]

Hi,
I saw the word Mini and had to investigate :-) (have owned 2 of the things!)

Why don't you remove the vacuum assisted brake servo and change it for an older type (1990 or earlier from memory) non assisted cylinder? Surely that would simplify matters.

I was looking to do a similar conversion. Perhaps with a Mini Estate/Van for more battery space.
2 (or 4!) agini motors. With one or two proving direct drive to each driveshaft. Not sure if it would fit?! Can agini motors be stacked up or 'siamised'?

N

[MalcolmB]

Originally Posted by Huff

Hi, I saw the word Mini and had to investigate :-)

Welcome Huff!
Removing the servo would make things a lot easier like you say. Unservoed brakes can be very good on a Mini, but my wife has arthritic ankles so I fitted the servo for her. She wants to drive this car as well, and she's been very tolerant of my obsession for all things electrovehicular, so I reckon it's a concession well worth making

A Mini van or estate would make a great conversion, though it's becoming hard to find a good one. The company that made my glass fibre shell (Domino) also made a pick-up version, and I'd really like to get one of those.

I believe the Lynch motors can be stacked, not so sure about the Agni motors. The man to ask would be Jozzer (a member here). He has lots of experience with them.

[DIYguy]

Originally Posted by MalcolmB

Now to the first of many daft questions: I want to keep this conversion as simple (and hopefully cheap) as possible. I've been looking at options for providing vacuum and 12V power and the simplest way I can see to do that would be to use the tail shaft on one motor to drive a mechanical vacuum pump, and use the tail shaft on the other to drive a lightweight alternator. The question is, if I have the motors wired in series to a single controller, is the small difference in load on each motor likely to cause any problems?

Hi Malcolm,... just a comment on the ideas for vacuum and 12 volt power. I don't see your method as being the simplest way. Perhaps "simple" and "cheap" are mutually exclusive...not sure...but in my little brain a vacuum pump and DC/DC (or even just a battery with enough Ah) is much simpler. Vacuum pumps can be relatively inexpensive...depends on how much noise you like to put up with. DC/DC's aren't all that much either. I would say these devices are on the lower end of the cost spectrum for what you need. Perhaps you should just let the motors drive the car....??

Anyways, good luck!