Why one electric motor? - Sähköautot - Nyt!
What I imagine is a small pan motor that fits next to and attaches to disk brakes. Although this will increase the sprung mass somewhat, the control of each wheel will give the electric car handling and grip only achievable from only the best of AWD vehicles. The other advantage is that more of the original components of a vehicle can be removed making room and reducing weight allowing for more batteries.
Some additional thoughts on this; 5 to 10 KW unit per wheel will be fine, need to be pan motors to fit against the hub/disk assembly and must be light as possible to keep the sprung mass down. Gets them out of the way so can fit more batteries or run a lighter vehicle - only moving parts will be disk calipers, wheel bearings and the motor shaft. We should be able to create the entire assembly (wheel bearings, disk brakes and electric motor). Regenerative breaking will naturally fall out of this, meaning each wheel will be able to generate about 10 - 20 KW of braking before resorting to disk brakes.
There are a lot of pros and cons. One larger motor is usually much cheaper than four smaller ones. Only one controller is required and a simple control. A fancy control system providing the exact required balance of power to each wheel does have advantages in terms of handeling, and anti-skid. However the cost goes up and if one wheel drive should fail there must be a safety interlock to remove the matching one also to avoid torque steer. The main thrust of this project is to provide a low-cost conversion, not build the highest performance car, therefore a single motor is the best choice.
Piilota Re: Why one electric motor? luonutIf you connect the left and right side motors in series, that will effectively work as a differential. It balances itself automatically, because when you drive into a corner, one motor is slowed down while the other speeds up. This effectively changes the voltage distribution between the motors and thus redistributes the power so that the car doesn't try to pull itself straight. Exactly what the mechanical differential is supposed to do.
And conversely, if you connect the motors in parallel, it works as if the differential was locked.
The only difficulty you have then is to provide front-back balancing of power. Or if you're content with two wheel drive, you can do with one controller only, perhaps with a throw-over switch to lock your "differential" in case you get caught up in snow or something.
Wiring two motors in series as described sounds ideal. However it pre-supposes that the motors are DC. Now the proposed motor is a DC Brushless design, which means that there is an internal AC controller so you are already paying for two controllers! If the motor was a brushed DC motor then you have lower efficiency, more maintenance and lower power.
Piilota Re: Why one electric motor? luonutAs far as brushless designs are concerned, they function just the same as their mechanically commutated counterparts. Try taking two ordinary DC fans from a computer and connect them in series. See what happens when you stop one or the other.
From my experience, those little brushless DC motors do exactly what they're supposed to do. In series configuration, both turn at a low rate since their voltage is now halved, and when you stick your finger in one, the other one speeds up. The other one won't get up to full speed, though, since these kind of motors present a significant resistance to the current even when stopped. A high power high amperage motor would practically short circuit when you jam it.