looking for a thread
 

the one that explains how kv, voltage, and rpm work
tried to search it but with no luck

voltage * kv = rpm

Done!

ummmm........thanks for the breif explanation but I want the the one that eplains how low kv motors run cooler and more efficient with higher voltage and why

because they do!! lol. in the spirit of real advice, id as brianG or cooleocool

low KV/ high voltage pulls less amps so it runs cooler lol, cant find a thread about it

This one?:
http://www.rc-monster.com/forum/showthread.php?t=12697

yes sir that is the one Hoov

Lower Kv motors have more torque and require less AMPs to make the same power as a higher Kv. Simply put it this way:

8S lipos 29.6V X 60A = 1776W (That was the AMP spike I saw in my 8S set up with a Neu 1515/2Y 1100Kv)

6S lipos 22.2V X 80A = 1776W

4S lipos 14.8V X 120A = 1776W

Amps is what will cause most of the heat and the lower the amp plus the torque of a lower Kv motor will give you a cooler running set up. I can also run smaller capacity packs ranging from 2200mAh - 3700mAh 8-10S lipos. he other factors will be gearing, weight, drivign style and smoothness of drive train.

That's basically it. The combination of HV and a lower kV motor do pull less current for a given power output. They are more efficient because electrical losses are dependent mainly on current draw. A high kV motor on lower voltage can make the same power, but it draws much more current and that high current creates more heat. Heat = lost power.

The bottom line it is. Is that a guy on the far right?

You're getting all the right answers for all the wrong reasons. :)

The higher voltage is the reason for the lower amp draw, not the KV of the motor. If you're doing the same work, you're doing the same work. If the efficiencies of the motors are the same, then the heat level is going to be the same. If we assume all of those motors are equally efficient at 90%, then they'll radiate 177.6w of heat, regardless of current draw.

The only way to make the same power with less heat is to get a more efficient motor.

Not true losses increase with square of current W = I * I * R...

Do you have first hand experience? I do with all the set ups I mentioned. Guess which one runs cooler and longer. Try it out and then tell us how a 8-10S with the appropriate Kv motor compares with a 4S set up and again with the appropriate Kv motor. What you saying will work on paper, but in real world I've found out that it doesn't work out. The numbers I posted was for AMP spikes and the avg. I get from my 8S set up is only 5A while I've seen over 10A with 6S. I haven't had much data on 4S, but with a similar set up as the 8S I've found that my ESC, battery and motor were all much warmer. I've heard of guys avg. over 20A on a 4S set up and that's where you see losses due to heat. You can have all the watts, but electric motors also makes power from torque and that's where a lower Kv motor (Brushed or Brushless) will have the advantage.

Yes, that's correct. Higher voltage will be more efficient.

Torque produced by a BL motor is a function of the can length. Once you saturate the magnetic field, they all make the same torque. So a 7700kv can make the same torque as a 4600kv, provided you can supply enough power to saturate the coil. Once it's saturated, all the power in the world won't change matters. If you want more torque, you need to go to a longer can.

This is further backed up by Castle's site:

and this:

So low kv does not equal more torque.

Castle Creations (With the Chinese slotless motors) is new to the brushless motor scene compared to Aveox (Neu included since Steve used to work at Aveox), Plettenberg, Lehner, Hacker, Mega and some other companies. Yes the can length has to do with torque mainly because of the length and/or diameter of the magnet. Take a lower turn Kv Nue motor and put it against a higher turn Kv motor and see which one has a higher Kt. I know first hand that my Neu 1515/2Y has more torque than my Neu 1515/1.5Y. I thought the .5 turn difference wasn't going to be noticed, but it is not by much though. Aveox has a nice way of calculating all of this, but I only have PDF files of it. I'll probably take a screen shot and post it here.