Drivetrain
Last Update 18-Jun-2003 by Mark
Electric Car Drivetrain
26-Sep-2002
Hmm - the drivetrain.
An electric motor has a much flatter torque curve than a petrol engine. It can give huge amounts of power at zero RPM.
So, do I need a gearbox?
If I don't use a gearbox, and just connect the motor directly to the driveshaft or diff, I'll need to use a diff ratio that gives me a good compromise between high and low speed performance.
Too high, and the car will take off like a snail.
Too low, and it will redline below highway speeds.
The PRB guys don't provide other diff ratios as a factory option, but they've suggested that I should be able to get 3rd party crown and pinions to sort it myself.
If I do use a gearbox, I'll only really need two gears (high and low), and no reverse (since the motor can be reversed electrically).
Exploring the gearbox path a little further, the cheapest option is to use a standard four or five speed gearbox. I've heard that it is possible to remove the unused gears to save weight.
Alternatively, Bert Transmission makes two speed gearboxes for speedway sprint cars. They're in Canada, and will sell me a gearbox for $1299 US, plus shipping.
(Hmm - I think I might go gearboxless for now...)
18-Nov-2002
Another thing to consider - the E2V Kit-E-Cat uses a toothed belt to give a 1.5:1 reduction before going into the 3.9:1 diff (about 6:1 total reduction from motor to wheels).
The Bob Brant book has a whole chapter devoted to torque curves, gear ratios and motor outputs (unfortunately all in Imperial measurements) which I'll have to convert to metric one day...
This will give me the information I need to decide one way or the other.
26-Jan-2003
OK, enough mucking around. I'm going to use a gearbox.
The standard box that the Clubmans use is a Ford Sierra 5-speed from England.
So, I'll have to find out about getting an adapter made up for an Advanced DC 9" to Sierra gearbox.
(KTA services say they have a whole bunch of different adapters - I wonder if they have this one?)
07-Feb-2003
I've been talking to David Probin (see Resources) and he'll do an adapter plate between the Ford gearbox and the motor.
There's one major problem solved.
I do, however, need to source a Ford bell housing. The gearboxes for the Clubmans come without since they have a custom made bell housing to bolt to a Toyota motor (which is rather expensive)
Luckily, the Sierra gearbox is very similar in shape to the old Cortina four speed, and a bell housing from one of these boxes should suffice.