Another mini conversion

Have you made or bought a converted vehicle if so this is for you
MalcolmB
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Joined: Sat Jun 23, 2007 8:07 pm

Postby MalcolmB » Wed Aug 27, 2008 11:39 am

Yes, it was the thought of the leading edge of the brush digging in and bouncing that worried me, but the commutators look very good so hopefully that won't happen. Thanks, I'll take your advice on the temperature sensors. Can you recommend one – I'm not sure what to look for.

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Jeremy
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Location: Salisbury

Postby Jeremy » Wed Aug 27, 2008 3:53 pm

If you don't want to reverse the direction of one of the motors, then you could look at arranging them in a staggered stack, both facing the same way and driving the shafts through chains/belts of different lengths.

You might be pushed for room a bit with this approach though, as the Mini has inconvenient stuff sticking out of the firewall, like the brake master cylinder.

Jeremy

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nino500
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Location: Isleworth, Middlesex

Postby nino500 » Wed Aug 27, 2008 7:12 pm

Yes, I was just thinking the same but if they were arranged at about 90 degrees (one down in the subframe, in front of the shaft and one against the bulkhead, above the shaft) you could still use identical drive components.

MalcolmB
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Joined: Sat Jun 23, 2007 8:07 pm

Postby MalcolmB » Wed Aug 27, 2008 7:58 pm

Thanks. I was trying to measure up this afternoon. It looks pretty tight in there but I think they'll just about fit the way you suggest, with one above the shafts and the other in front. I'd considered this arrangement before but didn't like it because it would put a fair amount of weight on one side, but then I realised that it counterbalances me, so that's OK :)

I've been thinking about different ways of mounting the motors and sprockets and providing adjustment for chain tensioning. One advantage of using a mini is that parts are in ready supply and relatively cheap. I've barely got enough garage space to turn around in so I'm planning to buy another mini subframe so I can play about with different mounting ideas. I enjoy fabrication but like to take my time, so progress is likely to be slow...

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Jeremy
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Location: Salisbury

Postby Jeremy » Wed Aug 27, 2008 8:05 pm

Malcolm,

I guess that you may have already worked this out, but did you know that you can interchange the drive shaft inboard ends to get them both of an equal length (if that helps)?

I did stacks of work years ago to try and make a new straight cut diff for my old race Cooper S that allowed equal length drive shafts. If you've tried putting Lotus Twin Cam torque through standard Cooper S shafts with a LSD you quickly learn that the car leaps sideways as you launch, due to unequal length drive shaft wind up (Amongst other things).

To swap the shafts you just need to keep the outboard ends handed as they were originally, but it's easy enough to take the CV joints apart and swap the inboard ends around. It may give you a bit more freedom with motor location.

Jeremy

MalcolmB
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Postby MalcolmB » Wed Aug 27, 2008 8:20 pm

Thanks Jeremy, I didn't know that and it could certainly come in handy. I don't know much about minis, so I've been reading up on the different drive shaft variants, trying to work out which are easiest to adapt. Mine is based on 1275GT running gear, with the inboard pot joints. Looks like the Hardy-Spicer couplings off the Copper S would make things easier though.

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Jeremy
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Location: Salisbury

Postby Jeremy » Wed Aug 27, 2008 8:50 pm

Although those pot joints give the smoothest drive, as they are CV type couplings, the Hardy Spicer inboard joints are the strongest. They weren't just fitted to the S, some of the other Cooper variants had the same couplings, but with thinner drive shafts (S shafts were thicker to take competition abuse, as the S was originally just a bit of an homologation special to get lots of special parts classed as production).

You'll also find Hardy Spicer couplings on the inboard ends of the automatic variants and on some of the later Morris 1100/1300 series cars. The worst couplings of all are the original rubber ones with the U bolts. Complete pigs to assemble and prone to going very soft and squidgy. There was a neat Quinton Hazell mod kit that swapped out the rubber for nylon cones, with proper bearings. These are nearly as good as the Hardy Spicer inboard ends, in some ways better as you can separate the inboard drive shaft end without needing to split the suspension ball joints and pull the shaft out.

I still have the scars on my knuckles from dealing with recalcitrant Mini inboard rubber couplings............

Jeremy

andylaurence
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Location: Bristol
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Postby andylaurence » Sat Nov 08, 2008 2:26 pm

I'm working (exceedingly slowly) on something similar. I'm still in the process of sorting out the 'shell of my Mini. I've got lots of lightweight panels to go in (carbon boot floor, bootlid and front end) and Perspex windows to lose weight from what needs to be there. Anything that's not needed is coming out. I've removed nearly everything and will be making holes in the subframe to get the weight down.

I've not even bought (or specced) what I need for the conversion yet. I said I was slow! I'm planning to use two short shafts and one motor chain driving each wheel. I'm gunning for lots of performance as the car is going to be used mainly for AutoSolos and probably sprinting too. I expect to be using lithium cells as they're allegedly capable of 30C continuous and should fit neatly on the floor. I should really be in the garage now, not posting on the forum here!

Cheers,
Andy

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qdos
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Postby qdos » Sat Nov 08, 2008 5:29 pm

Hey Andy some folk don't even have a vehicle yet and are still talking about an EV Conversion after years of chatting about it. You don't need to go calling yourself slow! :lol:

MalcolmB
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Postby MalcolmB » Sat Nov 08, 2008 8:02 pm

Hi Andy, sounds like a good project, would love to hear more and see some photos when you’ve made some progress.

I haven’t made much headway myself yet, as work keeps getting in the way, but I did manage to do some Blue Peter CAD modelling of my motors to see how they fit on the subframe. I’ve realised that although it would be possible to mount the motors to drive the wheels independently it would be too messy for my liking. This approach would work much better with a pair of shorter motors that could be mounted directly above the drive shafts. I also found that even using 8 mm pitch HTD belt drives, the driven sprockets would be too big (around 250 mm) to give sufficient road clearance with a single-stage reduction to each drive shaft.
(By the way, for anyone interested in using a belt transmission I’d recommend downloading the Design Flex software from Gates: http://www.gatesrubbercompany.net/desig ... DesignFlex)

The latest plan (liable to change at any time) is to go with a two-stage drive with the motors mounted as shown. The motor tail shafts (on the left side) will be coupled together by an 8 mm timing belt. A belt will then run from a sprocket on the right side of the front motor to a jackshaft mounted below this motor, giving a 2.5:1 reduction. The final drive will be by chain from the jackshaft to a chain drive diff, giving a further reduction of just under 2:1. This means that both motors will be rotating in the same direction, so I don’t have to worry too much about mismatch between them. I’m also hoping that the lower speed of the second stage will keep chain noise and wear to a reasonable level.

Next step, when I find time, is to get a local machine shop to machine a sprocket to fit the tapered shaft and to drill and tap the ends of the motor casings so that I can advance the motors.

Image

PS. You might be interested in this conversion, using a Suzuki Swift gearbox. It sounds as if the Australian lad who did it intends to sell full instructions: http://www.killawatt-electric-car-conve ... -mini.html


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