Hi All !
First of all, thanks for this forum and for all the topic already opened, it helps a lot !
Like many people I guess, I’m going through the question of the motor.
We are oposing 2 thinks:
- Inrunner with Gearbox
- Outrunner with direct drive
The only real question for us I think is the torque.
My question is: How to estimate the torque ? I know the basic physics behind it but struggle with one question regarding the 56104SS motor.
This motor’s specs tell 500kv, 11kW, 116A max and 88V max BUT, we are all using 12S (44V) batteries.
Does this means that the actual power with 12S batteries is not 11kW but half (5,5kW) ?
This is a pretty big deal for me since it’s change my equation by a factor of 2 !
If I’m correct, I’ve calculated the following torques:
56104 SSS Inrunner motor:
Max speed at 44v: 22 000tr/min (2 303rad/s)
Max torque : 5 500/2303 = 2,4 Nm (If my assumption regarding the Power at 44V is true !)
With 5:1 gearbox:
Max speed: 4400 tr/min
Max Torque: 12 Nm
6384 100Kv - 4000W
Max speed at 44V: 4400tr/min (460 rad/s)
Max Torque: 4000/460 = 8,7 Nm
As we can see, the difference between the 2 setups is not that big, especially if we take into consideration the many loss that the Inrunner + gearbox setup implies (gearbox loss + more bearings).
Do you guys agree with the maths and the “Power theory” ?
This would help me take the right decision a lot