Having thoroughly discussed wheelmotors on here, I think it’s time to change subject completely and talk about wheelmotors.
Yes, you did read that right, and no I haven’t lost it.
Several home-built EVs, especially ones done for-cheap (For instance, Forkenswift), they’re done with DC motors taken from old forklift trucks. Usually the “drive” motor is used, and all is well. But flicking through the Princess Auto catalog a little while ago (What else do you do at 2:30am when you can’t sleep?), I came across a few interesting things, not least were some small, but reasonably spec’d Hydraulic motors. (I can’t link to them, their website is stupid – If products have the same name, you can only see one of them!) A little more digging, and I find a set of things called “Inline Axial-Piston” motors, which have great characteristics (Torque up to 83 ft-lbs (each!), top speeds of 3-4000 RPM). So my thinking is that, perhaps, one could take the “Pump” motor from a forklift, hook up some high-pressure hoses, and have the basis for a very space-efficient vehicle. With no need for drive shafts at all, it gives all kinds of space for batteries, and if you were custom-designing your vehicle, you could have a flat floor with the batteries inside (Using thin cells like LiFePO4 laid on their sides, for example), a small “Engine” compartment with the motor, controller and hydraulic splitter, and just some high-pressure hoses going from there to the wheels. Driving the motors in series/parallel would give reliable performance with behaviour like a limited-slip differential, and the difference in displacement between the pump and motors will act as the gearbox. And the units themselves are reasonably small and light, which completely throws away the whole “messes up the handling” problem.
But I’m no hydraulics expert (Heck, I wouldn’t know where to begin, to be honest), so ideally what I’d really like is for some hydraulics guru to take a look at this and tell me if I’m nuts for considering it. I know hydraulic drive is used in some low-speed vehicles (dump trucks, forklifts, that kind of thing). So why not high(er)-speed situations like this? We don’t need all 3000 RPM (heck, with 15” wheels and average tyres, you reach 120KPH (75MPH) at 1185RPM! 1500RPM would suit perfectly (give a little leeway for the racers out there :) )), but we do need the torque and power. Ideally, this system should also drive backwards. Not only for reversing the vehicle, but to be able to drive the motor ‘round, giving the option of regenerative braking too.
So, someone who has an idea what to do with these pipes and things, drop me a line and let me know if this’ll work or not.
