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Old Oct 13, 2011, 04:52 AM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,807 Posts
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Speed E-pro motor question

I have a question for you motor guys out there, Both my motors are e-pro's, first one is 3231/22, 1440kv, 70g, operating current 16amp with 28 peak/15 secs.

Second is 3238/12, 1300kv, 104g, operating current 25amps with 35 peak/ 15secs.

Ok I have the 1440kv in a hyperion 400 series cap232, with 8x4apce and static it pulls 25amps so it should unload in flight to hopefully around 16amps ?. All good.

So I decided to check out the 1300kv for another project, I expected the larger and lower kv to pull a bigger prop, so for a starting point I wanted to start with a 8x4apce, to my surprise the amps draw was 30amps, how can this be, surely the larger/ lower kv motor should of returned less amps ?.

Regards Gary
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Old Oct 13, 2011, 06:37 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,000 Posts
I can't find any specs on those motors, who sells them?

Knowing their ratings in Watts is usually most helpful, you can compare the results you are getting to what the maker says the motors are good for.

You don't mention the battery but if you did, that, and the current readings you got, would let us estimate the power in Watts. Typical quality motors produce about 3 Watts of power per gram of motor weight so your two motors should be good for about 210 watts (3 x 70) and 312 Watts (3 x 104) of power.

Jack
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Old Oct 13, 2011, 02:23 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,807 Posts
Hi thanks for the reply both motors were tested on the same battery for consistancy it was a 3s 3700mah, this would not be the battery the motors will be used with (unless I did a twin), I got these motor while on holiday in HongKong from a shop here is their link, http://www.waigohobby.com/products/p...name=Outrunner the props they recommend are not even close.
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Old Oct 13, 2011, 02:44 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,000 Posts
It is kind of strange that they do not mention watts or amp max or min in the specs there. They say 2S/3S LiPO for both of them and have them needing 30A and 50A ESCs.

So if you figured the 3S at 11V against the ESC ratings, they would be something less than 330 Watt (11V x 30A = 330W) and 550 Watt (11V x 50A = 550W) motors. But getting 330W and 550W out of a 72 gram and 104 gram motor is very unlikely as that put them up in the very unrealistic 5 Watts per gram range.

I guess you are just going to have to warm them up with some props and figure out how much less it is. Do you have a watt meter?

I usually down rate the imported ESCs at about 75% of their rated value to give a little more of a safety margain. If they say the motor needs a 30A ESC I would use a 40A ESC in a cheap import.

Jack
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Old Oct 13, 2011, 03:54 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,807 Posts
Quote:
Originally Posted by jackerbes View Post
It is kind of strange that they do not mention watts or amp max or min in the specs there. They say 2S/3S LiPO for both of them and have them needing 30A and 50A ESCs.

So if you figured the 3S at 11V against the ESC ratings, they would be something less than 330 Watt (11V x 30A = 330W) and 550 Watt (11V x 50A = 550W) motors. But getting 330W and 550W out of a 72 gram and 104 gram motor is very unlikely as that put them up in the very unrealistic 5 Watts per gram range.

I guess you are just going to have to warm them up with some props and figure out how much less it is. Do you have a watt meter?

I usually down rate the imported ESCs at about 75% of their rated value to give a little more of a safety margain. If they say the motor needs a 30A ESC I would use a 40A ESC in a cheap import.

Jack
Yes I have v1 hyperion emeter, but confuses me is that the larger/lower kv should of spun the prop easier, I didnt expect these sort of results, the 1440kv flys really nice and judging by how my 1800 3s pack is on landing, which is quite warm but not what I would call hot.
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Old Oct 13, 2011, 07:07 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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Are we sure the Kv's of these two motors are actually what the stated specs suggest! The so-called 1300 might be a lot higher than that, and that might be why it draws more than the so-called 1440Kv.
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Old Oct 13, 2011, 07:23 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
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Quote:
Originally Posted by Dr Kiwi View Post
Are we sure the Kv's of these two motors are actually what the stated specs suggest! The so-called 1300 might be a lot higher than that, and that might be why it draws more than the so-called 1440Kv.
I thought of that so I recorded voltage and rpm and divide them into each other and came up with something like 1220kv for the 1300.
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