# Planning 1979 Mini conversion...



## MalcolmB (Jun 10, 2008)

Hi Imortl

I like the contrast in your first photo, makes the new Mini look like an SUV.

It would help us to offer relevant suggestions if you give some idea of your performance goals, budget and mechanical experience. 

I did a quick search for "mini" and came up with these threads:

http://www.diyelectriccar.com/forums/showthread.php?t=64941
http://www.diyelectriccar.com/forums/showthread.php?t=71039
http://www.diyelectriccar.com/forums/showthread.php?t=74058
http://www.diyelectriccar.com/forums/showthread.php?t=67066


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## IMORTL (Sep 1, 2012)

Thanks for the links Malcom! I had actually come across your build earlier when browsing through the site. Quite an impressive setup you have there with the dual motors.

As far as performance goals, I'd like to be able to hit decent highway speeds and have a range of at or around 50 miles. I've been looking at the Warp9 based on some previous recommendations (or the smaller Impulse9 depending on space ... haven't gotten to the sizing stage yet)

Budget is just really as I have the money. It's a hobby for me so I'm not looking to stick to a set dollar amount. Cheaper the better, but if it's worth the extra money then I'm all for it.

As far as mechanical expertise ... little to none. Although I pick things up pretty fast and have a few friends to lend a hand here and there to help out.


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## Ziggythewiz (May 16, 2010)

For 50 miles, lithium's really you're only option. Something like a warp9 backed by 144V of 100AH cells would make for an awesome little car


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## MalcolmB (Jun 10, 2008)

The Warp or Impulse 9 should easily meet your performance needs with the right controller and battery. Space is reeaally tight, so I'd go for the smaller motor. Personally I'd like to try another conversion using the Kostov 9" 144V, or even the 96V version – they're about the same length as the Impulse 9, and only weigh 45 kg.

Have you thought about whether you want to use a gearbox or not? Clutch or no clutch? Any of the motors above would be good for a single-speed drive. With a gearbox you could actually use a smaller motor.

I've been using a figure of 200 Wh/mile for energy calculations, though I'm hoping for less than that. A 50-mile range would require 10 kWh, plus 25% margin: 12.5 kWh, pretty close to Ziggy's 100 Ah 144V pack.

It would be a mortal crime to put lead in a mini – Alec Issigonis would turn in his grave – besides, I reckon you'd have to remove the front and rear seats from a mini to stuff in enough lead for 50 miles.


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## IMORTL (Sep 1, 2012)

MalcolmB said:


> Have you thought about whether you want to use a gearbox or not? Clutch or no clutch? Any of the motors above would be good for a single-speed drive. With a gearbox you could actually use a smaller motor.


I have been debating this. A single-speed drive would definitely be nice as it would be less complex and I'd lose the weight of the gearbox. But I'm guessing the downsides are less range/top speed? Sorry if these questions are rather elementary, I'm trying to learn 

I'd love to be able to autocross this guy, and in auto crossing you usually stick in one gear anyway and never near any type of top speed to speak of.

I'm looking into the Kostov motors now. The weight difference would definitely be a plus!


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## Ziggythewiz (May 16, 2010)

No gearbox doesn't directly affect range, but means less acceleration and top speed, unless you can find a fixed gear ratio that will give you acceptable numbers at both ends.

For example, I only use 2nd, which gives me good acceleration but I top out at 45 mph (3rd would be sluggy on low end but up to 60). I could do a direct to a custom diff that gives the the same end ratio, but then I wouldn't have the option of changing gears to do 70+.


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## IMORTL (Sep 1, 2012)

Ziggythewiz said:


> No gearbox doesn't directly affect range, but means less acceleration and top speed, unless you can find a fixed gear ratio that will give you acceptable numbers at both ends.
> 
> For example, I only use 2nd, which gives me good acceleration but I top out at 45 mph (3rd would be sluggy on low end but up to 60). I could do a direct to a custom diff that gives the the same end ratio, but then I wouldn't have the option of changing gears to do 70+.


Yeah I think in this case I'd want to do a gearbox.

Also, looking at the Kostov K9 vs. the Warp9. The Kostov is lighter by about 40 lbs and a few hundred dollars cheaper than the Warp9. The Warp9 appears to have better torque/HP numbers though.

With a vehicle this light would it be better to go with the nominal weight savings of the K9 or the nominal torque/HP advantage of the Warp9?


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## Ziggythewiz (May 16, 2010)

I don't think 40 lbs would make much of a difference, but you're probably good on power either way. I'm only running a 6.7" and not even at full power, so any good 9" should be great.

Be sure to check shipping costs as sending a motor overseas may affect your comparison.


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## Duncan (Dec 8, 2008)

Hi
As a long term mini man 
(I had an S and a mini convertible with a 2litre twin cam before I was married)
I was very tempted to use a mini shell for my project

Anyway I decided on a Lotus 7 type instead

When you think about gearbox - or not the logic I used was

I got a nice ford gearbox - 

then I calculated how much torque I would get at the back wheels

With my (large) motor I calculated that I would spin the wheels in top gear

At that point I removed the gearbox!

With a mini I would try and find a suitable diff from a car with independent rear suspension and drive - Subaru?

Bolt the motor to the top of the diff with a gear drive down to the diff

Look at putting enough amps through the motor to spin the tyres

Guess-timate
9 inch motor 
150 ftlbs = 600Amps
4.1:1 diff = 615Ft lbs at front wheels
Mini wheels - 18 inches in diameter? 
Force at tire/road interface = 615 x 12 / 9 = 820 Lbs - 
Front of a mini weighs - ~ 850lbs??
Good tires give a friction factor of 80% - 80% of 850lbs = 680lbs force
That will definitely spin your tires!
That would give 45 mph at 4000rpm or 67 Mph at 6000 rpm

Probably want to give away a little torque to get higher gearing


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## MalcolmB (Jun 10, 2008)

Ziggythewiz said:


> No gearbox doesn't directly affect range, but means less acceleration and top speed, unless you can find a fixed gear ratio that will give you acceptable numbers at both ends.


I wouldn't try to discourage anyone from using a gearbox, but it could work pretty well for a car as light as a mini. With a fixed ratio of between 3.5:1 and 4:1, and a motor that produces 130 ft lbs of torque, you could get 80 mph top speed and 1/3 g acceleration most of the way to 60 mph with a well-matched controller and pack.

The Warp 9 would probably be best suited to this approach, as it's a relatively high-torque motor.

Duncan managed to post while I was writing this, looks like our figures match well.

Edit: Wheel diameter with 12" tyres is a shade over 500mm, surprisingly it's not much different with 10" tyres.


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## EVEngineeer (Apr 11, 2012)

Finally another person from south Florida! Can't wait to see your progress, being in the location your in! I have noticed that there really isn't that many places to get help in Florida at all. The only person that I hear is reputable is steve clunn in Fort Pierce. I can get there but it would take a few hours of driving. Good Luck


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## Yabert (Feb 7, 2010)

MalcolmB said:


> I wouldn't try to discourage anyone from using a gearbox, but it could work pretty well for a car as light as a mini.


I also think this. 
That work very well in my 865 Kg Smart Fortwo when I only used third or fourth gear (fast 0-65 mph in third and good 0-83 mph in fourth). I use a Warp Impulse 9 with Soliton 1 (1000A).
A Warp 9 can be way more impressive in a light mini.


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## EVEngineeer (Apr 11, 2012)

I sent you a private message. Please respond when you get the chance.


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## Arch (Aug 21, 2011)

I can't offer any advice, but Woody showed me this thread. My first (and so far only) car was a 1979 Mini that colour (although mine had a light beige roof). The pictures took me right back!

(And reminded me just how ludicrous it is that that 'thing' has the name 'Mini'. It's vast....)


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## IMORTL (Sep 1, 2012)

Thanks everyone for your replies. I'm trying to educate myself as best I can and you guys have been a tremendous help.

So far, not much progress to speak of. Working on getting a rotisserie built so I can do some body work on the Mini. All in all a bit overwhelming since this is my first project of the sort, but I'm trying to take it one step at a time 

EVEngineer I sent you a private message back ... sorry it took 5 months to reply ... lol

As a sidenote, I've been very interested reading about the (quite old now) electric Mini QED. One thing that I noticed was that it has a small on-board ICE that serves to recharge the batteries when you're not able to plug in somewhere. I've noticed this is pretty popular and something that even the Tesla does to get its range up while still being a completely electric-drive vehicle.

I was wondering what the DIY applications might be here if any? I see small, lightweight, efficient generators like this one. Is this something that could be integrated downline of the charging management system to "top off" the batteries as they get low before a plug-in? Or does weight and efficiencies of these type of things make them generally not worth it?


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