How to determine efficiency? + Inrunners for direct drive
 

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.

The smaller 3040 will disipate less heat than the 3080 and therefore will have a lower maximum power output assuming the same efficiency.

With the lower wind count/bigger wire of the 3080 its maximum efficiency will be at a higher amp draw than the 3040.

Luckily Lehner is one of the few companies that supply efficiency curves for their motors, so decide how many amps you are going to run then look at the graphs and pick the one with its maximum efficiency in that range.

I know Lehner have made 3080s with shafts out the front and back for a boater who made a twin drive cat with 4x 3080s 2 coupled together on each side, it would have to be a special order from Lehner directly but they are happy to help, I guess Neu would be the same.

Yes, thank you. I've been looking at those efficiency curves and they are quite helpful.

Have you checked out Castles Garage sale on their motors just to see if there is something that might fit your application?