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Originally Posted by maxxdude1234
Apart from this statement, I fully agree with you last post. The 8L and 8XL can produce the same power at a given voltage, if they are both geared to achieve the same speed. However, if they are both geared optimally, then they will achieve different speeds and hence have different power output
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Well, if we clear with the rest, then let’s think about both systems.
At given voltage (12 cells) 8L with fixed load will draw current I(8L) which generates torque T(8L), based on motors magnet size and windings; 8XL - I(8XL) and T(8XL).
If we try to normalize torque values from 8L and 8XL we need to introduce coefficient responsible for size difference (magnet, core, windings…). This coefficient will be RPM dependant or more precisely efficiency curve mirror.
So Motor torque for 8L = n(8L)(RPM)*T(8L) and 8XL = n(8XL)(RPM)*T(8XL).
Now virtual experiment:
8L (Kv 3079) on 12 cells with fixed load spins at 30000 RPM’s and draws I(8L)A
8XL (Kv 2084) on 12 cells with the same load spins at 23000 RPM and draws I(8XL)A
If I(8L) equals I(8XL) then Total power equals, but shaft power differs.
And based on motor size and guys feedback I will say that I(8L) should be higher.
So what we have then? 8L has higher current meaning higher torque, but because of smaller footstep has lower coefficient “n”. While 8XL has good size and great “n” but barely has current to create that torque.
Without good motor I-V-RPM curves we can discuss that forever.
Artur