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Old 05-05-2014, 06:23 AM   #8
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Dennis V
 
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Originally Posted by RVDriver View Post
ok guys everyone explains how they work somewhat, but why is one better than the other? I buy a plane RTF it has a motor/esc/battery, why should I change it? Does is Battery life (run time) better with one over the other?

Now with my Car or Motor Home I buy the largest 12v battery I can make fit in the required Space. (Minnesota Winters require more Starting Ampe than Florida/Texas Winters)

Just bought a Super Cub S and after it fly's Ok, I plan on adding floats, some say prop change is needed others say larger motor, then others say it just flys a little slower.

So What should I plan on doing ?

Motor Size: 480-size brushed motor (installed)
Prop Size: 9 x 6
Battery: 11.1V 3S 1300mAh LiPo battery (included)
You might be starting a can of worms here

From my perspective, having owned a number of $$$$ Astroflight brush type motors up to about 900 Watts, brushless is the way to go.

You've probably got a few battery powered tools like drills and so forth. These are all brush type units. Problem is with brushes, with the physical space available in a typical model motor, those brushes can't handle much more than about 30 Amps. Push them to hard, and they won't last more than a season of flying. Or maybe much less.

Going on to brushless motors, the required switching of the motors windings is done electronically. These motors are essentially a three phase AC motor with a variable frequency drive. These electronic switches can handle a surprising amount of power, far exceeding that of a brush setup. It's not hard to come up with a brushless motor that can handle over 1000 watts, or about 1.3 horsepower. For a lot more $$$$, brushless motors rated for over 3000 watts are readily available. How much more power than a brush type motor? Numbers vary, but double the watts on the propeller for the same weight of motor, brush vs brushless type would be reasonable. These brushless motors can usually swing bigger diameter propellers than a brush type unit. That's why brush type units often use a reduction gearbox.

I've had three different models that started out with a brush type motor, namely the top of the line Astroflight motors, back in the mid 1980's. These motors were upgraded with the $$$$Hacker motors, using the same battery pack, and same airplane. Performance immediately increased, and at the same time, flight times were longer.

For the real small, tiny models, a brush type motor works just nicely. Once you get to a wingspan of perhaps 20 inches or more, brushless motors start to make sense.

The circuitry behind those brushless motor controllers is extremely complex, along with even more complex computer software used to drive that circuitry. How does it work? "Very Well!".

Name brand Electronic Speed Controls along with quality brushless motors can easily outperform a glow engine in the same model. Only problem is, brushless motors are limited to perhaps 6-8 minute flying time, where a glow engine can double that flying time.

So, do you need to pull the brush motor out of your model, and upgrade to a brushless?? If you are happy with how your existing model flies, no reason to upgrade, at least IMHO. For your next model, just add brushless motor to its requirements.

Hope that helps.

DennyV
Retired and the days are just too short, busier than ever!
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