I’m coming from the ebike world and looking at what motors to buy for a skateboard, and I haven’t seen any good empirical comparisons between the different motors available. People say things like “these motors are super powerful” or “I can climb a 100% grade hill no problem,” which are horribly inconsistent, so inspired by this thread comparing Raptor 2 hubs to Hummie hubs, and this ebike motor comparison database, I want to build a spreadsheet of actual scientific numbers for as many motors as possible.
Fortunately, you all have fancy computers attached to our motors that can measure all the necessary parameters called VESCs. So can you guys post screenshots in this thread from the VESC tool for your motors, and I’ll add them all to the spreadsheet? What I need is the Motor Resistance from the FOC tab, and the measured kV of the motor. To measure the kV, remove the belt if you use one, then run the motor at full speed, and type
kv into the terminal several times so we can average the numbers, and it’ll return the kV in eRPM/V, and then you divide by the number of motor pole pairs (usually 7) to get the actual kV. A mass number for the motor would be nice to have as well, but not necessary.
With the motor resistance and kV, we can calculate kM, the motor size constant, a measure of how much torque the motor can produce for a certain amount of heat output. Larger motors with more copper have a higher kM, so they will heat up less and have a higher current rating. But unlike current ratings, the kM is a more fair comparison because it doesn’t depend on things like airflow or motor kV, and can be measured much more easily. With the mass of the motor, you also know the kM/kg, a measure of how lightweight the motor is built for its power level.
I added numbers for all the motors I could find, which unfortunately doesn’t include any eskate hub motors. Initial results show that the Turnigy SK3 6374-149kV blows all the other belt drive motors out of the water. Like, the numbers Hobbyking gives are so good I’m suspicious of them. Let’s verify those numbers, and measure some hub motors!