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Brushless motor size and power

Old 10-10-2005, 11:19 AM
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Default Brushless motor size and power

Dear all,
Please forgive my ignorance as I'd just started electric recently. I'm very confuse on the size of the brushless motor, esc amperage, batteries ( especially Lipo ) and all those technical terms on electric. I believe this question had been asked many times but I can't seems to find the old thread.
So how am I going to know what size is a brushless motor? Is it printed on the motor itself? I often see people describe their brushless as something like : 2 digits/ 2 digits/ 1 digit. What does that mean? If it is the power of the motor? So how am I going to know what esc goes with which size brushless? and what battery to go with the brushless or the esc?
Somehow it seems like I'm asking some silly question but this had been on my mind for a long time and I would like to admit that I really don't know.
I really appreciate if someone can explain to me rather than looking stupid when reading the forum on electric and not understanding what you guys are talking[]
Old 10-10-2005, 05:02 PM
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Default RE: Brushless motor size and power

Hopefully someone can give a better answer but what I do is go to sites that sell brushless motors
and they usually give as much detail as possible ??

This is from one site I use :
AXI 2212/20
Suitable for models of 300-400 is surprisingly powerful
No of cells 6-10, 3 x Li-Poly - RPM/Volt 1290 - Current Capacity 16A/60s - Dimensions 27.5 x 30mm - Shaft Di. 3.17mm - Weight 57g

It is a AXI 2212/20 brushless motor which could replace a brushed motor sized between 300-400 !
no off cells 6-10 are ni-cads and 3 x = lipoly's ESC upto a max of 16amp's weight of motor 57grams...

Most website that sell brushless motors will give help if you need to get motor/esc/battery from them !

Also what you need is the size/weight of your plane so you can get a motor with enough thrust !!

or as above if the plane takes a 300 to 400 brushed motor the AXI above would be a straight replacement....

Old 10-10-2005, 08:01 PM
Matt Kirsch
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Default RE: Brushless motor size and power

Let me start by saying that you can't hope to understand it all overnight. There's a learning curve, as there is to any worthwhile activity.

The concept of "motor does NOT equal engine" is one of the most difficult for people getting started with electrics to grasp. Forget about the numbers. They're meaningless physical dimensions, the diameter, length, and number of turns of wire in the motor. These numbers are absolutely useless for figuring out whether a motor will work on a plane, or not. I repeat, useless and meaningless. Use them to differentiate between motors, like you'd use F-150 and Silverado to differentiate between Ford and Chevy pickup trucks.

The important figures are the maximum cell count (or voltage) and maximum current ratings that every motor's specifications include. These are important because by the time you get to choosing the motor, you already know how much power you need, and what battery you're going to use. From a newbie's perspective, this seems totally backwards, but it's the only way to effectively power an electric airplane.

When you're starting out, though, I just recommend that you copy someone else's power system, or get help. It's much easier to learn when you have a working setup in hand so you can see how things go together. At this stage of the game, every size, shape, and type of airplane has been converted, so there's plenty of data out there to benefit from.
Old 10-10-2005, 11:58 PM
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Default RE: Brushless motor size and power

Thanks for all the valuable information. I believe I'll need to start up gradually as advised by Matt Kirsch. Matt, thanks alot.
Whiteghostuk, can a detail of the power supply be given if information on the plane is given?
Let say that I need to have a power equivalent to a glow of .40-.50. What power supply is suitable? Thanks again for your help.
Old 10-11-2005, 08:14 AM
Walt Thyng
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Default RE: Brushless motor size and power

My standard advice to all newbies is to log onto Ken Myers' Electric flight Only (EFO) site. It's an encyclopedia of e-power info. You can learn to size motors by reviewing the "Plane Ratings" section where e-power fliers review what works and what doesn't work for them. Ken also has an extensive article on "cubic" loading which he claims is a better way to determine power needs. The monthly e-letter Ampeer is one of the best available. There is a resource page which lists e-power vendors. A fantastic site.

[email protected]
Old 10-26-2005, 11:35 AM
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Default RE: Brushless motor size and power

One of the nicer things that e-power manufacturers could do would be to standardize their sizing methodology. It's frustrating and time consuming to try and figure out what size motors equal what in outputs at a base voltage. I don't think any two manufacturers use similar descriptions.

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