KV Rating on Motors
 

I'm looking at HiMaxx motors (3618) with planetary gearbox (4.3:1). There's 3 different models which have 2300, 3000, 4500 KV ratings. What does this term mean??? It was recommended to me that I use a TP 6000 Mah 3s3p battery. Would the different motor ratings effect battery duration, etc?

Thanks,

MPB

RE: KV Rating on Motors
 

the KV is the RPM(x1000) per Volt applied. The higher the number, the faster the motor will spin, and more apms will be drawn. A 3s lipo is 12.6v fully charged, 12.6v x 4500kv would =56,700rpm. so yes, it will affect the flight time. Higher kv= more power, less time
...... hope that was helpful ;)

RE: KV Rating on Motors
 

Another concept which helps to understand the whole KV thing is to know that if you apply a certain (same) voltage to a motor it will spin the same rpm regardless of what prop you have on it (or no prop at all!). Keep in mind this does require that the amps can be delivered to the motor as the prop size increases. As prop increases your amp draw will go up but if you stay at same voltage rpm remains constant.

RE: KV Rating on Motors
 

Actually, there is no factor of a thousand for those ratings... if it says 4500kv, that's 4500 rpms/Volt... not 4,500,000 rpms/Volt. The K is not indicating "kilo", but I believe the K in "Kv" is supposed to denote voltage gain of the motor... K is a common variable name for used for gain, and v is the subscript used to indicate voltage gain... for motor, the units would be rpms/Volt for such a gain...

RE: KV Rating on Motors
 

does it make sense to say then,,that simply put,,..the heavier the plane one is flying,,the higher the k.v rating they will probably need..ecspecially if they are going to go the outrunner route...with the drawback being of the higher rating..that the motor will draw more amps..and one will need to make sure their battery pack can handle the draw..as far as lowerr flight time..that can be somewhat compensated for with a little throttle management...for me..id rather go with the higher k.v rating..and have the speed/power there..if and when i want it...

RE: KV Rating on Motors
 

Yes, for a given number of cells, or pack voltage this is true. I see two ways to look at it...
1) Higher Kv means more RPMs per volt = more thrust/Volt (with same gear ratio & prop).
2) Higher Kv motors have fewer turns = lower resistance = higher current/Volt = more power/Volt.

With a given gear ratio and prop, you can increase your power by getting a higher Kv motor, or by getting a higher voltage pack. So Higher Kv motors can have the same power on a 2S pack as a lower Kv motor on a 3S pack.

I like to overpower my planes a little too, and just use throttle control to keep it "tame". For my foamie, I chose a motor with "optimum" current of 9-11A, and peak of 14A... my batt pack is 12A max (no peak rating, but it seems to handle full throttle for quite awhile w/o getting very warm), so this motor is pretty much the most powerful motor I can run with my batt packs. Another thing to consider, if you've got more power than you really need this... with the Castle Creations ESCs, you can tweak the motor timing, to dial back a little power and current, and get longer runtimes. I figure I'll run mine in the default mode first, and then consider dialing the timing back if I find myself at 1/3 to 1/2 throttle most of the time...

RE: KV Rating on Motors
 

The combo I went with is a 3618 3000KV 4.3:1 planetary geared motor, 45amp CC ESC, and the TP 6000 3S3P battery. It's going in a 3.5 lb 3D plane (that's total flying weight, with all the mentioned stuff included). This should be a fun plane. I've never tinkered with "timing" yet. I guess I'll get some flight time with this set up first.

RE: KV Rating on Motors
 

well..be carefull with tinekring around with the timing setting of the phoenix esc..I emailed castle on that very subject..and they basically told me to leave that setting at the factory preset mode...so i did...lol...

RE: KV Rating on Motors
 

I'd worry about advancing the timing, since that would make the motor run hotter (and possibly get more power out of it), but not retarding it, or going to a more neutral timing from the default setting. That will actually make it run cooler, and give you longer runtimes, at the cost of some performance. That's probably a canned response from Castle, since most guys that want to muck with timing are looking to advance it, and possibly fry their motors because of it...