Another example of twin motors is the White Zombie street legal electric drag car. It uses 2 8 inch motors coupled one behind the other with a series/parallel switch over that changes how the motors recieve their voltage. Ends up with a 1970 or 72 Datsun doing a <12 second quarter mile. Pretty impressive watching it clean the clock of corvettes, bmw's, and nearly everything else out there. He's really open about how it works. Another is a Pinto out of Alaska called Crazy Horse. Ultimately running 2 motors or more produces twice the torque but does use a lot more battery. Great for getting speed, lousy for range.