My new contraption

[kfxguy]

Some of you guys I'm sure have one of these things. I'm posting this because since I've been a member here, I haven't seen anything about it.....so...

It's a hobbyking kv meter (I don't buy from hobbyking, so I got it from kintec). Pretty nifty little unit. I decided to mount it, an esc and a servo tester to a board. The servo tester works perfectly in the place of a receiver and transmitter, plus I thought this was much more convenient. Turned out decent and serves it's purpose well. I had an old junky mamba esc that didn't work but I fixed it to be mounted permanently. I tested a few motors (got excited!) And came up with interesting results.....

Castle 1518 1800kv tested at 1836kv (dang close!)
Castle 1515 2200 kv finned old version tested at 2305kv (hot motor!)
And a new style castle 1515 non finned 2200kv tested at 2176kv (little low)

Pics...






I have some things I want to test......ceramic bearings, messed up bearings (just to see how much they rob you!) And I have a motor with two different length rotors, the long one is supposed to bring the kv down...I want to see the difference.

[olwarbirds]

Interesting Gadget Travis, be nice to have...I could use one now to compare the twin 1515 2200 I'm putting in the Fantasm....DJ

[785boats]

Very good Travis.
I've found a few motors in the spares box & I've got no idea what the kv ratings are. No markings or labels. I've always meant to get a meter to check them. I'm inspired now.

[Make-a-Wake]

Very cool innovation there. Do yo have to run the motors at WOT to get the kv..........is that harmful if so?

[kfxguy]

Very cool innovation there. Do yo have to run the motors at WOT to get the kv..........is that harmful if so?

You do run them wot but on a low voltage (1s to 3s). Not harmful unless your pushing it too hard (example 3s on 6800kv motor lol)

I think that motor was turning 25,920rpm (thats what the tach said) so it wasn't breaking a sweat.

[Make-a-Wake]

Thanks, that makes sense that you can run low voltage since its only measuring "per volt". You got a Castle 1717(1580kv) or 2028(780kv)? Wondering what they are.

[kfxguy]

Thanks, that makes sense that you can run low voltage since its only measuring "per volt". You got a Castle 1717(1580kv) or 2028(780kv)? Wondering what they are.

I dont have either but if you do, I'd check it for you. I'm about to check my 1527.....

[kfxguy]

My 1527 1y checked in a 2336kv.....I thought it was a fluke so I plugged another motor in and it checked in at the right kv....Plugged 1527 back in....same thing. What's the chances the motor being labeled wrong?


Edit. Double checked the neu chart....it's definitely supposed to be 1250kv. I'll recheck it this evening. Weird.

[olwarbirds]

Travis, sounds like its a 1D brother. Dont make sense that your other motors test close and just one be that far off. Put that on 6S and hold on...I got to put together a test setup like this too... DJ

[runzwithsizorz]

My 1527 1y checked in a 2336kv.....I thought it was a fluke so I plugged another motor in and it checked in at the right kv....Plugged 1527 back in....same thing. What's the chances the motor being labeled wrong?


Edit. Double checked the neu chart....it's definitely supposed to be 1250kv. I'll recheck it this evening. Weird.

Weird indeed, that's just way too far off. On the bright side, a Neu 2300kv 1D sells for $45 more

[keithbradley]

You have to use the esc with this one?

FYI: In my experience, the calibration of these testers varies a lot from one tester to another. It will be useful to compare your own motors, but not to compare to someone else's findings or manufacturer's specs.
Obviously the 2300kv motor is well outside calibration variation though. Is there a 2pole/4 pole setting on your tester?

[Fluid]

An interesting contraption, good work. I have a similar setup but yours is far more professional looking, and probably works better. Question - do you check the actual loaded pack voltage when calculating Kv?

Too, realize that a motor's Kv will change under load. For example, my 1515/1Y has a Kv of 2128 at 4 amps, but it drops to 2043 at 50 amps and 1946 at 100 amps.

Your 1527/1Y test value is about twice what it is supposed to be. Like Keith I suspect a wrong pole setting somewhere - if it is really 2300 then you would have burned up your ESC the first time you tried running it in a boat (when assuming it was a 1250 Kv motor).


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[kfxguy]

You have to use the esc with this one?

FYI: In my experience, the calibration of these testers varies a lot from one tester to another. It will be useful to compare your own motors, but not to compare to someone else's findings or manufacturer's specs.
Obviously the 2300kv motor is well outside calibration variation though. Is there a 2pole/4 pole setting on your tester?

Everything I've checked so far (3 other motors) were very close to what they are rated at. It does have a pole setting. It say to divide y 2. So a four pole would be set at number 2. That's where is set. I'm gonna check a few more motors this even in yes you must use an esc. I chose the mamba because I feel it's pretty steady.... do you know of another tester that does not require an esc?

[kfxguy]

An interesting contraption, good work. I have a similar setup but yours is far more professional looking, and probably works better. Question - do you check the actual loaded pack voltage when calculating Kv?

Too, realize that a motor's Kv will change under load. For example, my 1515/1Y has a Kv of 2128 at 4 amps, but it drops to 2043 at 50 amps and 1946 at 100 amps.

Your 1527/1Y test value is about twice what it is supposed to be. Like Keith I suspect a wrong pole setting somewhere - if it is really 2300 then you would have burned up your ESC the first time you tried running it in a boat (when assuming it was a 1250 Kv motor).


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Few things....

First, thanks for the compliments!

Next, I think the kv is calculated with the total voltage put out. The tester knows rpm and voltage. I guess it simply calculates it so whatever voltage drop it has, it's compensated for. Just wot is all that matters. I'm not putting a load on it, just want to know my kv, no load. Btw, the voltage drops only .01 for a second when I ramp up throttle.

If it is 2300kv ot makes sense. I had it in my shocker with an x447/3 and it ran about 130 degrees pretty quickly. Visually it looked faster than I thought it should be...now that I think back on it.....

[kfxguy]

I looked and the only info I could find was that the 15 series are all 4 pole....I had it set to number 2 (which is how you do it, divide the number of poles in half and that's your number you input. It does not change settings each time I use it either...but I did check to make sure. I'm going to call neu today and see if it's possible they labeled it wrong.