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Old Apr 29, 2010, 09:14 PM
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CurtissP40's Avatar
Northwest Oregon
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Brushed speed 300, 400, 480, motors vs brushless motors

I am building a plane that was designed for a brushed motor. Since I don't have any brushed motors, I want to substitute a brushless.

After trying a number of RC Groups searches without success, can anybody point me to a comparison of brushed motors versus brushless motors? A chart or table showing how speed 300, 350, 400, 480, etc motors relate to watts, KV, Amps, Volts, etc of brushless motors.

I am aware that there are likely many factors in such a comparison, but all I need is a rough idea to help kick start my decision.

TIA
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Old Apr 29, 2010, 11:18 PM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
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The field is vast.
Tell us which model or what size brushed motor and if it is direct drive or geared.

Graupner Brushed specs
http://www.modelflight.com.au/graupn...ifications.htm
Replace brushed w brushless
http://www.wattflyer.com/forums/showthread.php?t=1129
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Old Apr 30, 2010, 04:45 AM
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Nowadays, there is a huge range of motors on offer. You should be able to find a motor which ideally suits your model.

This was not the case in the "stone age" of brushed can motors.

Choosing a modern motor on the basis of equivalence to an ancient can motor cannot be reccommended.
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Old Apr 30, 2010, 12:17 PM
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Quote:
Originally Posted by CurtissP40 View Post
I am building a plane that was designed for a brushed motor. Since I don't have any brushed motors, I want to substitute a brushless.
Quote:
Originally Posted by peterangus
Choosing a modern motor on the basis of equivalence to an ancient can motor cannot be reccommended.
Is it just me or is that a completely useless statement with respect to the original question?

Anyway.
GWS IPS system 15-20W
speed 280 25W
speed 300 50W
speed 400 80W
speed 480 120-150W
speed 500/550/600 180-200W.
Buggy motors and other quality 550/600 systems 250-300W.


Don't worry about KV, since the above needed gearboxes anyway, and are all in the range 2000-3000KV.

Generally 900-1400KV motors will do a better job.
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Old Apr 30, 2010, 02:32 PM
Glow 😡 no no no
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Quote:
Originally Posted by peterangus View Post
Choosing a modern motor on the basis of equivalence to an ancient can motor cannot be reccommended.


I get what peter is saying and tend to agree with him, eg. a speed 400 is about 72 grams and a brushless of the same power output might be about 26grams?. while this seems to be good, it can lead to CofG problems because the motor is too light. Ofcourse a brushless motor of the same weight will overpower the plane lol.

What a shame lol.
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Old May 01, 2010, 04:04 AM
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nothing says you cant put weight or a big motor in the nose and run it at less power by using a smaller prop.

Sheesh.
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Old May 01, 2010, 05:53 AM
Glow 😡 no no no
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Quote:
Originally Posted by vintage1 View Post
nothing says you cant put weight or a big motor in the nose and run it at less power by using a smaller prop.

Sheesh.


Lol now thats too simple. Nothing like overpowered models.
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Old May 01, 2010, 03:23 PM
An itch?. Scratch build.
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Perhaps the easier way is to decide what prop and battery you want to use, and select a brushless to turn it at a suitable rpm.

Motors on their own don't fly planes very well. (Unless you like slope soaring )
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Old May 01, 2010, 03:25 PM
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Preferably don't add weight, rather try to move the battery forward to correct balance
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Old May 01, 2010, 04:51 PM
Glow 😡 no no no
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Quote:
Originally Posted by Terry Pieters View Post
Preferably don't add weight, rather try to move the battery forward to correct balance
Plus bigger battery longer flight time and easier on the battery.
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Old May 01, 2010, 05:14 PM
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There was a formula about watts per lb and was generally used to size brushed motors to a specific weight and size palne and type of flying.

50 watts, a speed 400 motor, would fly a 1 lb plane anemically, a 12 oz plane pretty fast, and would probably keep a powered glider at 24 oz airborne (barely).

a speed 480 motor would be maybe 75 watts and would fly a 1 lb plane pretty good, a 1.5 lb plane anemicall, and a powered glider of 2 lbs could climb very slowly.

Speed 600 would fly a 2 lb plane OK, and a 3 lb plane marginally. Figure its 150 watts.

So a brushless motor would do the same. Maybe you want to get a bigger size one that would weigh the same as the brushed one, and then prop it down, or use a fewer cell count battery.

What is the plane you have anyway? Look at Hobby Kings site. They must have 100's of different motors. Beware the out-runnner and the back-mount stylee. They require you to employ problem solving skills to attach to the front of the plane sometimes, but this is probably what you will wind up using. They can be screwed to the firewall, but the brushed motors are not mounted this way. They can be mounted like a brushed motor, but you will have to figure out how to get the wires away from the rotating part of the motor.

HK has a small out-runner encased in a sleeve that would solve this problem. There are also inrunner motors with low Kv, that is they are lower rpms and can swing a bigger prop.

Why don't you post the name of the model and someone can tell you what they have done with theirs? Brushless motors are pretty much vastly superior to any brushed motors I am aware of. Jake
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