View Full Version : Brushless general info for newbies

10-19-2005, 07:53 PM
And again LOTS more info. This is what helped me figure out why and what brushless was and why I wanted it!

Brushless motors offer several advantages to the modeler. -

First, there is less radio noise generated to interfere with the remote control. This will increase the reliability of the remote control and extend the operating distance.

Second, when a brush motor spins fast, the brushes will tend to "fly" over the commutator, causing arcing and heating, thus lowering efficiency.

Third, the effective resistance of the brushes is much higher then that of the MOSFETs that are electronically commutating a brushless motor, especially at high currents and temperatures.

Foremost, brushless motors can fit much more copper inside (thicker wires) than a brush motor of equivalent size, thus lowering resistance, increasing efficiency, and increasing torque.

Because of these facts, brushless motors have the inherent capability to spin faster and operate at higher currents, to produce more power, without the performance deteriorating. Since all the commutation of the motor is done electronically, the overall reliability of the system is much higher.

The goal of any motor designer is to maximize efficiency in a motor without sacrificing performance. The energy from your battery is used up in two ways: kinetic (moving the load) and heat (friction and I2R losses). High power brush motors tend to have high frictional losses due to their large brushes and high spring forces, which are necessary to handle high currents. Brushless motors do not suffer from these frictional losses. Greater efficiency due to more copper and less resistance means more energy goes into kinetic and less into heat. This extra energy can either extend running time or increase power output.

Since motor efficiency is largely dependent on the volume of copper (amount of wire inside) in the motor, brushless motors yield much better performance than a brush type motor of the same size because more copper can be packed on the outer radius of the brushless motor than on the inner radius of a brush motor. This allows a thicker gauge wire to be used. The windings run cooler because they have a direct thermal transfer to the case. This increases efficiency because copper has a lower resistance at lower temperatures. This allows a much higher peak and continuous output than a brush motor of a similar size because there is less danger of over heating. The magnets also stay cooler because the heat is radiated outward, away from the magnets. Also, the lower rotating mass allows the motor to spin up faster because of the lower inertia.

11-03-2005, 12:47 PM
Interesting info, but very hard to read as one solid block of text. May I suggest you try using paragraphs for readability.

11-03-2005, 02:31 PM
Better? :p I hate reading large blocks too. I was in a hurry the night I did all of those so I got lazy.;)

11-03-2005, 02:40 PM

Much! :D

11-03-2005, 03:10 PM
Super Much! Thanks!

11-03-2005, 05:06 PM

11-03-2005, 06:42 PM

That would be where I found it most likely. I dont know if you were the one complaining earlier about copyrights, but I stated in my first thread that I wasnt sure where all my info was from and that I had just gathered it from many long nights on the computer. I dont save links, they go bad all the time, I save info that I find useful into text documents on my pc. I like one site or source where I can get info instead of surfing all over the place. I have tons of info saved from the many hours that I was searching, and I still search constantly.

I also apologized in advance if any of the info I posted was in fact copyrighted and that most of the info was not mine. If this info is yours, great stuff, it helped me out. You are more than welcome to post who you are and if its yours.

p.s. - I suppose you could say that all the info I posted about figuring out brushless motor designations are copyrighted as well since they are all from manufacturers specs. Again, my posts meant no malice towards anyone, I was just trying to make it easier on someone who didnt want to search all day.

11-03-2005, 08:35 PM
Not a problem. I just don't like to see uncredited information cut and pasted from other people's websites. They will often have put a lot of time and thought in writing that useful stuff. It seems to me polite to at least post a link to the original. Plus of course anyone following the link can often find all sorts of other interesting information on the same site.

Even if you haven't saved the link it's very easy to look it up (e.g. paste the first sentence into Google) but if you haven't got time to do it I'm happy to do it for you ;).


11-04-2005, 01:28 PM
Can I just add a note for newbies on a tight budget.
You don't have to go brushless to enjoy rc models, or lipo batteries.

Brushless motors are better, and lipo's are lighter, (weight can be very important).

But if you can't afford them yet, you can still get a lot of fun from cheap brushed motors, nicads and nimh batteries.

I have been flying electric for the past twenty years, and have only just bought my first brushless, still haven't got round to buying any lipo's yet.

So newbies, if your on a tight budget there's no excuses not to get out there and enjoy flying electric models.

11-04-2005, 02:48 PM
I completely agree e-ray! I am still running brushed motors on everything I own. My first brushless package is on its way now though. I have a feeling once I turn to brushless, I will be adding them slowly to my other planes! Same thing with the Lipo's, dont have any (yet!). With new thumbs still, I am finding that really high quality NiMh are working just fine.

Matt Kirsch
11-04-2005, 05:18 PM
Yeah, but the gap is closing quickly.

On my latest Shockflyer:
Motor - Potensky 50W outrunner brushless: $24.90
ESC - Great Planes SS8: $29.99
Battery - Kokam 340 3S: $27.99

That's at most double the cost of a brushed system for this plane. It's lighter. It's more powerful. It's more efficient. It'll last virtually forever.

11-04-2005, 11:33 PM
I am still flying all brushed and NIMH.

I purchased my first brushelss and my first Lipo but have yet to fly them.

11-05-2005, 01:43 AM
Like others here I have just for the first time last weekend flown a brushless plane. Although I have yet to use any of the 3 LiPo packs I now own. There is nothing wrong with using brushed power sets and nicad/nimh batteries however the price gap is narrowing so the improved performance and excellent durability of BL power and Lipo batteries are fast becomming a no brainer.

11-26-2005, 11:10 PM
I can not say enough about a brushless. Started with a Sig Kadet that came with a brushed motor and burned up two, using a Li-Po 3 cell and not staying out of the throttle (a good tip). Now I have replaced the brushed motor with an E-Flight Park 450 and the Kadet is a different plane :) No more problems...