KV / Gearing choices

[crazyjr]

Originally Posted by Finnster

Yeah, the prop loading is imperfect, and it only gives you a fixed point as an output, but I do think it gives some interesting data when it comes to motor load, which we can kinda equate to hard accel or WOT. You can use the max eff point for a given voltage to kinda create a dynamic range, but its "eh".

I was intending to address the question posed by glassDr in previous post.

Basically, if you have a fixed voltage (eg 5S) and are trying to gear to the same speed (prop rpms~=wheel rpms, ie 40mph) is it better to use a lower kv motor and overgear, or a high kv motor and gear lower?

The calc data to me says "lower gear, higher kv" is better. This makes sence to me as well as in my Novak BL example from above as well, that a 8.5 can not be ran as fast as a 5.5 on the same # of cells as after a point the motor becomes overgeared and just becomes hot (data indicates that motor will draw more amps, but eff falls, so output power does not improve.)

=> if you want a truck that does 40 on 14 cells, its more efficient to run a (8)XL and lower the gearing than run a 10xl and gear high.

Obviously there are more factors involved in actual motor selection, but this is what the calc data and my own experience tells me.

Based on this thread I have been wondering if i needed to run a 7XL instead of the 9XL in my G2R 12 cell mamba max setup. Given the same gearing (17/66) and same cell count (12 cells), Could the 7XL be more efficient in this case?

[Dafni]

CrazyJR, now you feel my pain :) I was wondering the very same thing, but with different motors.
You'd have to change the gearing though. Aim for the same speed, and your motor temps may significantly drop.
Whatever you do, please keep us updated.

Daf

[starscream]

Originally Posted by Dafni

CrazyJR, now you feel my pain :) I was wondering the very same thing, but with different motors.
You'd have to change the gearing though. Aim for the same speed, and your motor temps may significantly drop.
Whatever you do, please keep us updated.

Daf

Here's another question that seems relavent to this conversation. The neu motors seem to be built with both Delta and Wye winds. The Wye wind seem to have a lower kv than the Delta. Is one wind type more efficient than the other?

[Finnster]

Originally Posted by crazyjr

Based on this thread I have been wondering if i needed to run a 7XL instead of the 9XL in my G2R 12 cell mamba max setup. Given the same gearing (17/66) and same cell count (12 cells), Could the 7XL be more efficient in this case?

As daf said, you couldn't gear it the same. Assuming both are properly geared, it doesn't mean the 9xl is inefficient, altho it may be just slightly lower. What you can't do is try to gear the 9xl for as high of speed as the 7xl is capable of w/o overgearing/overloading the motor and thus dropping efficiencies

SScream: you evil man....:mad:1 :005: I doubt and diff would be readily noticeble, all winds seem capable of v high efficiencies.