9 replies to this topic

[MalcolmB]

Right, a bit unusual this one, but I really hope one of you mini geniuses (genii?) can help...

I'm converting a mini to electric drive. I plan to mount toothed drive pulleys (actually large karting sprockets) on the inboard ends of each drive shaft to drive each front wheel independently with a pair of motors. The problem is that the pulleys are a good bit bigger in diameter than the diff casing, so they foul on the rear web of the subframe. I need about 15 mm more clearance at the rear of the subframe. It's easy enough to modify the rear of the subframe to provide clearance, but the real problem is that the steering rack sits just a few millimetres behind it at almost exactly the height where I need most clearance. What I'd like to know is, is it possible to move the rack backwards about 10 mm or so without upsetting steering geometry? I remember reading that someone sells a thinner steering rack, but I can't remember where. Any suggestions?

Cheers
Malcolm

[Udo]

Can't you simply use smaller sprockets? Must be the easier option and use the pinion on the motor to alter gearing if required

Never heard of a thinner rack

[MalcolmB]

I'd use smaller sprockets if I could, but I need the highest reduction ratio I can get and I'm already using the smallest motor sprocket I can get away with. Below a certain tooth count the wrap radius becomes too tight and you get excessive belt wear...

[Saxo-Fiesta-Mini]

well u could move the rack up you can mount the tie rods upside down but ull need to one adapt the steerin colum , cuts some holes and redrill where the brakets are for the steering rack that shud work also make sure to get it 4 wheel tracked afterwards to be safe

Edited by Saxo-Fiesta-Mini, 10 March 2009 - 07:56 PM.

[il-barba]

you cannot put tie rods upside down because the steering arms are tapered

[MalcolmB]

OK, just crawled out from under t'mini after peering and probing and measuring. There's not much wasted space under there is there? Come to the conclusion that I'm not going to create more space without some serious modifications, which I don't fancy. I'm just going to have to compromise and move the pot joints forward about 10-15mm from their usual position. That shouldn't make any real difference to efficiency should it? It works out at around 2 degrees deflection.

[bigmotherwhale]

shouldnt be too bad, 15mm isnt very much, it would be beter than moving the rack, that would change how the car rides, bump steer ackerman angles etc... all the things i try to avoid thinking too much about.

hows the hunt for bateries going? your going to use lead acid arent you? il be keeping my eye out on your progress cant wait to see it run.

another thing is why didnt you mount the motor ontop of the gearbox and run 4 gears? seems alot easyer. how powerfull are the electric motors you have? wont one do?

[Dan]

What Mini have you based this on? Very late carb and all injection Minis have the engine mounted about 12mm further forward than earlier models do. If your car is from earlier than about 1992 moving the whole lot forward 15mm won't be a problem but if it's a newer model adding another 15mm might start to cause a problem with the plunge depth of the joints even if the angles are fine. You might have to move the joints a bit further apart than they are as standard to compensate.

[MalcolmB]

Very late carb and all injection Minis have the engine mounted about 12mm further forward than earlier models do. If your car is from earlier than about 1992 moving the whole lot forward 15mm won't be a problem but if it's a newer model adding another 15mm might start to cause a problem with the plunge depth of the joints even if the angles are fine. You might have to move the joints a bit further apart than they are as standard to compensate.

Very useful information there Dan, I didn't know about the engine being further forward in later models. Thanks for that. I'm converting a Domino (fibreglass mini lookalike), which was built around 1990, I think. Fairly sure it's pre-1992 anyway. It would actually help if I could move the pot joints out a little as I'm pushed for space between them as well. I'm already using a pair of short driveshafts to get as much space as possible. Every millimetre counts on this one.

I've already got a starter battery pack just to test things out: 108V of second-hand Hawker Genesis 40Ah lead acid. Once I've got things running properly that'll be replaced with lithium ion, most likely from LifeBatt.
Mounting the motor on top of the gearbox has been done before. I just fancied something different. I had two motors anyway and figured by using both it would double the torque and do away with the need for a gearbox, as well as giving more power. The motors are rated at 5 hp continuous, but it should be possible to get 40 hp from each of them by running at higher voltage and using an 800A controller.

Edited by MalcolmB, 14 March 2009 - 07:28 PM.

[bigmotherwhale]

are you still planning on running the motors in parallel?
also i was thinking it might be possible the other day to run 2 types of battery pack together by running a constant current off the li polymer untill you have enough li poly to take over completely, using the lead acid for there pulse discharge rating and the li poly for there ah, if you see what i mean - does sound pretty complex tho

oh are you planning on getting a regen braking controller?