Another mini conversion
Posted: Sun Aug 03, 2008 10:24 am
I bought a mini a few weeks ago with the express purpose of doing an electric conversion. My motorbike is great fun and I learned a lot building it, but I eventually plan to sell it and put the proceeds towards lithium batteries.
I haven't actually started the conversion yet as I still have lots of questions to answer, so I'm hoping I can get some advice here before I get out the grinder.
So far I have the donor car and a pair of series wound motors I was lucky to get cheap
The motors are 14 inches long, 7.25 inches in diameter and weigh 40 kg each. Although they're only rated at 36V I've been told on pretty good authority that it should be possible to run them at up to 120 volts by advancing the brushes around 10 degrees. This means rotating the brush plate counter to the direction of rotation of the motor, which looks to be fairly easy to do.
The plan so far is to use two of the motors at 108V, probably with a 750A controller. I’d like to stick with the existing front wheel drive and get rid of as many oily bits as possible, including the gearbox. I’m hoping that by using two fairly powerful motors I can get sufficient torque for takeoff. Final vehicle weight should be no more than 700 kg.
The options I’ve been looking at so far are:
a) Driving each front wheel independently with belt drives to the inner ends of the drive shafts. The motors would be connected in parallel and act as a limited slip differential.
b) Coupling the motors side by side with a timing belt drive, and using a second belt to take drive to an enclosed differential, like this: http://www.westhouse.plus.com/chaindrive1.htm
The motors would be connected in parallel again.
c) Either option a or b, but with a system of contactors that allows the motors to be switched from series to parallel. This effectively provides an electric gear change, switching the motors from high torque / low speed to low torque / high speed.
Although c) sounds good, I’m a bit worried about the complexity and cost of the contactor arrangement required, so I’m leaning towards a) or b).
Sorry this is so long, but I’d be really grateful if anyone could tell me which of these options is likely to work or if they have any alternative suggestions.
Malcolm
I haven't actually started the conversion yet as I still have lots of questions to answer, so I'm hoping I can get some advice here before I get out the grinder.
So far I have the donor car and a pair of series wound motors I was lucky to get cheap
The motors are 14 inches long, 7.25 inches in diameter and weigh 40 kg each. Although they're only rated at 36V I've been told on pretty good authority that it should be possible to run them at up to 120 volts by advancing the brushes around 10 degrees. This means rotating the brush plate counter to the direction of rotation of the motor, which looks to be fairly easy to do.
The plan so far is to use two of the motors at 108V, probably with a 750A controller. I’d like to stick with the existing front wheel drive and get rid of as many oily bits as possible, including the gearbox. I’m hoping that by using two fairly powerful motors I can get sufficient torque for takeoff. Final vehicle weight should be no more than 700 kg.
The options I’ve been looking at so far are:
a) Driving each front wheel independently with belt drives to the inner ends of the drive shafts. The motors would be connected in parallel and act as a limited slip differential.
b) Coupling the motors side by side with a timing belt drive, and using a second belt to take drive to an enclosed differential, like this: http://www.westhouse.plus.com/chaindrive1.htm
The motors would be connected in parallel again.
c) Either option a or b, but with a system of contactors that allows the motors to be switched from series to parallel. This effectively provides an electric gear change, switching the motors from high torque / low speed to low torque / high speed.
Although c) sounds good, I’m a bit worried about the complexity and cost of the contactor arrangement required, so I’m leaning towards a) or b).
Sorry this is so long, but I’d be really grateful if anyone could tell me which of these options is likely to work or if they have any alternative suggestions.
Malcolm