How to determine efficiency? + Inrunners for direct drive

[moneybagsfor-rc]

Hey guys, been a while.

To power a new direct drive project of mine I have decided that I will purchase something from the 30XX line of Lehner motors or an equivalent Neu (how do you pronounce Neu? Is it English pronunciation "new" or German "noy"?). So I have a riddle about brushless motors and I'll give an example with the Lehners. What is the difference between:

3040 12 wdg - 875 kv 80mm length
3060 8 wdg - 875 kv 100mm
3080 6 wdg - 875 kv 120mm

Now I know that the 3080 should have more torque due to the longer can, so as a totally blind guess is the 3040 more power efficient? What is the tradeoff in motor sizes holding kv constant? Why would one person buy a 3080 6wdg and someone else buy a 3040 12wdg even though the kv is the same?

If it helps, battery power is 14s 5300mah Thunder Power G4 Pro race with 65C rating (cost: arm+leg. But the batteries are from other vehicles so really it was at no additional cost)


Second question: how can I convert a Lehner/Neu motor to be a direct drive 4wd like we see with outrunners? Finedesign does it for one of their inrunner motors, but they are not at all helpful.