KV / Gearing choices

[Serum]

the only other one i made in this thread.

[Procharged5.0]

Then the answer is yes.

I have almost no Mt experience, but have fought with this idea much, looked at many componies motor charts, called a few, and have had some good experience with my rc 18, some bl park flyers, my m.m. 5700 and spent lots of time on a prop calculator similair to neu's.
-torque of elec. motors is calculated in in.oz. per amp.
-A given kv motor makes a certain inch ounces of torque (per amp) regardless of motor size.
-higher kv motors make less torque (per amp) than lower kv, but if geared down to same rpm they end up with the same torque per amp after gearing.
-higher kv motor of a given size will handle more amps than lower kv (so high kv geared down=low kv as far as in.oz./amp, but high kv handles more amps so = more torque) *if the batts. can feed the amps*
-lower kv motors can handle more voltage without flying apart, and the higher resistence keeps the higher voltage in check on acceleration, so as not to spike to many amps (the lower the resistance, or higher the voltage the more freely the amps flow).
-every diffrent size, style, and kv motor has a difrent amp draw that makes it happiest, most efficient.
-motors of the *same size* and build have the same *watt rating*, but difrent kv require diffrent voltage and amp draws to achieve there maximum.(thin wire in 20 turn can't flow the amps of the thick wire in a 6 turn, and 6 turn would fly apart at the voltage the 20 turn could handle).

- every motor has its sweet spot. Diffrent styles of motors handle higher amp draws at lower kv, and have diffrent sweet spots. Out runners for example, have many poles and and can achieve low kv and higher amp draw for their size=lotsa torque not much speed(the rotating part is big diameter=lot of centrifigul force) but ideal for direct drive props, and trucks that otherwise require tons of gearing. The mamba motors are 2-pole they require 65,000+ rpm to get the most out of them, more would be better if it could hold together (the little mabas are 80,000+). Mega motors are 6 pole and are claimed to work well (achieve good wattage for size) @ 35000 rpms, however they are built to handle much more, 55,000 I believe. I have talked to airplane guys running 16-15's pushing twice the power a motor that size should handle, so high kv(for the type of motor) + high voltage + low gearing(or small prop) can equal much more power than a motor is rated for. These particular airplane guys were running ducted fans, so the motor gets lots of cooling air, and there realy is no spike on acceleration. Trying to overdrive a motor by pulling twice the amps would not work well at all though.
- Acording to the calculators as kv and voltage go up so does max. eficiencey, but @ the amp draw required to achieve max eff. wattage keeps getting higher and and colling can become an issue. On the other hand if kv and voltage stay the same potential eff. stays the same and adding gear or more amps drive actual eff. down after a certain point.
Nue motors I believe are 4-pole and I would quess 45000rpm would be a good point for geting all the power out. However sower was running a 6800 kv 1105 (2.3 oz. motor 200 watt) on 3s in a 4wd 10th scale buggy, and said it was "silly fast. fastest thing I've ever driven". So maybe with a very efficient, well built motor, they can be overdrivin with voltage, and still stay cool, without being in the middle of a ducted fan. *If you have enough gear to keep the amps in check.*
Another interesting example is jhautz 1/8 Buggy w/ a Outrunner Motor . I think that is a 5.6 oz. motor. have to see how it goes.

Sorry if a little of topic, but I think it depends on how close to the amp limit you are on the lower kv motor. Also for the esc's, the more poles the less rpm it can handle. I don't know the specs or limits, but idealy commutating a 6-pole at full throttle would be like comutating a 2-pole with 3 times the kv rating. not sure how much that would affect heat.

[Serum]

You are forgetting one important limiting factor in your post; the maximum magnetic force a motor can translate to a turn.

I personally don't like the high reving motors, from my own experience they get hot pretty fast, no matter if it's a 2 pole with segmented/non segmented magnets or a 4 pole (neu/bigmaxximum)

It's easier to heat up a fast reving low torque motor than a slower turning low kv motor. that's my personal experience.

A high kv motor also means more stress/loss for the controller. so is a 4 pole vs a 2 pole.