I'm building an electric go kart and I'm planning on using a 36v 1000w motor and I was told that overvolting it by 12 volts would increase the RPM's, but then what would I be looking at in terms of it lasting.
Assuming it is a 1.0 service factor and the type is a series motor, you would get right at 1/3 more RPM depending on the load. Motors being so different, some like a little high voltage some like low voltage, about the only way to really know the current draw is to measure it. I would not allow it to run anymore than 10% over rated current. Next is the quality of the motor, some AC motors ran off VFDS run at higher speeds than rated, but again current and load will have a huge effect. But back to your extra 12 volts, the internal components are designed to withstand a certain RPM. However some motors are built to the bare minimum design, others are built to withstand some overload. It's a big jump, but again a series DC motor is load controlled, we don't know the load, and only by measuring it will we. I would say it the chances are the motor lasting is going to go down by the amount of the over voltage. I would suggest you use some type of mechanical transmission to increase the wheel speed which is what I assume you are after. Again this creates different loads, so find a DC amp meter so you know where you are at, and mount it on the kart, a volt meter would be nice also.. A larger driver pulley[or gear] on the motor shaft and a smaller driven pulley [or gear} will give you more RPM at the driven pulley. Just like an automobile, there are transmissions to control the RPMS of the engine, at various speeds along with torque at various speeds. If you go to a bearing supply store, they will have a line of variable adjustable pulleys that can be adjusted in or out to increase or decrease the diameter, you might find a device like that very helpful. Direct drive is smoother and dependent again on the motor, would be a great drive train but you are talking a very sophisticated and expensive motor and controller.
