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Power Systems Talk about motors, ESC speed controllers, gear drives, propellers, power system simulators and all power system related topics

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Old 06-24-2013, 04:31 PM   #1
billbens
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Default How do I know what size my brushless motor is?

I have a brushless motor that I purchased a few years ago and never used for anything. It is a 2830, 1300kv motor. I have a text file on my computer that I think gives some of the information on this motor. It is as follows:

Specifications
Rotational Speed: 1300 RPM/V
Continuous Current: 15A
Max. Current: 20A
Input Voltage: 6 - 16V
No Load Current: 1.5A
Internal Resistance: 112m ohm
Motor Dimensions (Diameter x Length): 28mm x 30.8mm
Shaft Dimensions (Diameter x Length): 3.13mm x 12mm
Input Battery Types: NiCd/ Nimh/ Li-po Battery
Recommend Model: RC Model Airplane
Recommended Propeller: 9 x 6 / 10 x 5 / 10 x 6
Net Weight: 56g


What I want to know is from this information should I be able to discern what size motor this is? I mean is a 380 or a 400 or a ???
If it is discernible from the information given how do I calculate it.
And just being lazy is there any chance this motor would be a decent replacement for the 480 brushed motor in a HZ Super Cub DSM?

I am an active member of some none RC forums and I know that in those forums some questions get asked over and over and it drives some of us old guys just about nuts. That is why I am apologizing in advance for this thread.
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Old 06-24-2013, 05:06 PM   #2
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Based on weight alone it's probably in the 380 to 400 range but there is no specific definition for what that means. The weight is the same as an E-Flite Park 400. You could probably get the Super cub to fly with it but I think you would be better off with something at least 70-80grams and 900-1100kv.
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Old 06-24-2013, 05:07 PM   #3
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Originally Posted by billbens View Post
I have a brushless motor that I purchased a few years ago and never used for anything. It is a 2830, 1300kv motor. I have a text file on my computer that I think gives some of the information on this motor. It is as follows:

Specifications
Rotational Speed: 1300 RPM/V
Continuous Current: 15A
Max. Current: 20A
Input Voltage: 6 - 16V
No Load Current: 1.5A
Internal Resistance: 112m ohm
Motor Dimensions (Diameter x Length): 28mm x 30.8mm
Shaft Dimensions (Diameter x Length): 3.13mm x 12mm
Input Battery Types: NiCd/ Nimh/ Li-po Battery
Recommend Model: RC Model Airplane
Recommended Propeller: 9 x 6 / 10 x 5 / 10 x 6
Net Weight: 56g


What I want to know is from this information should I be able to discern what size motor this is? I mean is a 380 or a 400 or a ???
If it is discernible from the information given how do I calculate it.
And just being lazy is there any chance this motor would be a decent replacement for the 480 brushed motor in a HZ Super Cub DSM?

I am an active member of some none RC forums and I know that in those forums some questions get asked over and over and it drives some of us old guys just about nuts. That is why I am apologizing in advance for this thread.
It's not so much what size motor, as it is, what kind of power can it handle, and what prop can it turn.

One of those computer programs such as www.motocalc.com will give you answers. Just create a "New Motor", and plug in the above numbers into the program.

Just using basic numbers, your motor is rated at 15 Amps and 16 Volts, which is Watts equals volts times amps or 240 watts. It weighs about 2 ounces, so they are running about 120 watts per ounce of motor weight. That number of watts per ounce is a little bit high, might be pushing the motor a bit.

DennyV
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Old 06-24-2013, 08:35 PM   #4
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Thank you both for the responses. I had seen something on on calculating the volts before. I just thought there might be some hard and fast rules for coming up with the size motor.
I also had my doubts about it being big enough for the super cub just looking at it. It is definitely smaller than the motor on it now, but I did not know if being brushless it might be enough.
I guess a larger motor with a lower kv is because I would need the torque?
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Old 06-24-2013, 09:48 PM   #5
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kv tells you the no-load rpm per volt. Higher kv motors will require comparatively smaller props than lower kv motors. With slow flying planes you generally want as big a prop as possible with less pitch commensurate with the expected speed. This gives the maximum thrust with desired speed. The same prop on a higher kv motor will draw more current and give a higher top speed. To keep the current the same you would have to reduce prop diameter or pitch. With the plane and motors we're talking about we're near the low end of available pitch range so you have to reduce prop diameter. If you do wind up with the same current and thrust it usually also means higher top speed. It's really all about trying to optimize motor current, rpm, thrust, and top speed within the flight envelope of the plane in question. Motor weight is an important factor in balancing the plane but it also is a real limitation on how much power the motor can handle. In general the more metal mass in the motor the more electrical power it can handle.
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Old 06-24-2013, 09:59 PM   #6
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The 3 main statistics:

Watts... power (usually measured as volts X current input... output is appx 80% to 90% if properly loaded)
The maker really should list max watts. Simply multiplying max voltage and max amps isn't a good idea. It may not be able to take both at the same time.

Volts input.

kV... the "voltage constant" for the motor... how many rpm it WANTS to turn per volt applied. Actual under load is about 80% to 90%

These 3 numbers will tell you the performance you can expect when using a battery in its recommended range and one of the recommended propellers.

Then adjust which propeller in the recommended sizes (or slightly outside.. with a wattmeter to check load) to get the aircraft performance desired.

That particular motor is in the 480-500 class.

It will fly a Hobby Zone Super cub just fine. More power than needed.
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Old 06-24-2013, 10:07 PM   #7
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Originally Posted by fhhuber View Post
That particular motor is in the 480-500 class..
The motor only weighs 56 grams. Hardly 480.
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Old 06-24-2013, 11:24 PM   #8
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id call it a decent 450. my heads up 450 sport weighs 2.6 ounces and is rated at 240 watts. they have a 450 speed that is more similar with 300 watts on 4 cells.

figure about 200-240 watts with a 10 x 5 prop should fly the plane fine.
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Old 06-24-2013, 11:41 PM   #9
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Heads Up Firepower 400 Sport is about the closest thing they have.

Weight, diameter, length, and shaft size virtually the same. lower kv though

peak: amps 17, 180 watts

http://www.headsuphobby.com/Firepowe...otor-E-630.htm
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Old 06-24-2013, 11:58 PM   #10
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yeah, with that low of weight, it would make a good brushed replacement for a 400 size.
on 3 cells.
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Old 08-13-2013, 05:33 PM   #11
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Another useful "rule of thumb".. most motors should be asked to cope with no more than 3W/g... so your 56g motor is probably good for ~180W max.
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Old 08-14-2013, 09:06 AM   #12
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Thats a good old common 2830 motor 1300kv , about a 400 size, it will fit a lot of planes well,

The Firepower 400 Speed (2830-13) is a 1.9 ounce, 1300KV, 220 watt, 400 class outrunner brushless motor. It's a good choice for sport planes weighing 12 to 32 ounces, and works best with 7 or 8 inch props and a 3 cell Lipo battery.

http://www.headsuphobby.com/Firepowe...otor-C-656.htm

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