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Help with prop sizes and electric motors

Old 07-26-2012, 01:54 PM
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Top cop
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Default Help with prop sizes and electric motors



Can any one help me.. I am confussed ref prop sizes for different motors. I have a Hacker A30 10 XL in my wifes Trainer. I am using 3 cell lipos. What would be the best size for this motor and best run time.

How can I get a better understanding of props. ie what is ment 14 X 7 E

Can anyone give me any giudence in tese areas and or other electric motor info.

Thanks
Mark

Old 07-26-2012, 02:24 PM
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Sherv
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Default RE: Help with prop sizes and electric motors

to get your started


http://www.rc-airplane-world.com/propeller-size.html


and you need one of these

http://www.hobbyking.com/hobbyking/s..._Analyzer.html
Old 07-26-2012, 02:27 PM
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Default RE: Help with prop sizes and electric motors

'ie what is ment 14 X 7 E'

14" diameter prop, 7 is the pitch, and the 'E' designates 'Electric" prop. I use APC. the ones I use are smaller, but I always buy the 'E' prop. Hope this helps. Also, my LHS has props behind the counter, si there I would ask for a 14 x 7 E, and they give me what I would ask for. Hope this helps a little.
Old 07-26-2012, 11:31 PM
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Bozarth
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Default RE: Help with prop sizes and electric motors

ORIGINAL: NEW222

'ie what is ment 14 X 7 E'

14'' diameter prop, 7 is the pitch, and the 'E' designates 'Electric'' prop. I use APC. the ones I use are smaller, but I always buy the 'E' prop. Hope this helps. Also, my LHS has props behind the counter, si there I would ask for a 14 x 7 E, and they give me what I would ask for. Hope this helps a little.

"7 is the pitch" means geometrically (i.e. theoretically without considering other aerodynamic stuff) the prop would move forward 7" after one revolution. A 14x4 would geometrically only move 4" forward after one revolution. You can think of the pitch as gears in a car. The lower the gear, the more power, but less speed.

"E" props are less robust than non-electric props. Simply go to the hobby shop and compare the bulk and thickness of a normal 9x6 compared to an "E" 9x6. The electric version props are less robust because they are not designed to reach the rpms of props normally run on nitro burning engines. APC makes two versions of "E" props. One is for slow flight and one is more for speed. The SF versions are the least robust, while the E speed versions appear closer to the conventional nitro props.

Follow the prop recommendations of the motor manufacturer. If you pick a different prop, you need to measure the amps. Too aggressive of a propeller (too large of a diameter or too much pitch) will pull too many amps and damage the battery, speed control, motor, or all three. Unlike nitro engines, using a less aggressive propeller will not damage an electrical setup. Using a less aggressive prop for a given battery/motor combination will simply produce less power. Increasing prop diameter/pitch on an electric motor is like screwing the needle valve in on a nitro engine - just don't go to far.
Old 07-27-2012, 02:13 AM
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Sherv
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Default RE: Help with prop sizes and electric motors

I have found the APC E props (non slow fly) to be more aggressively pitched, sturdy, and insanely sharp compared to the slow fly versions. I got lucky the other day where my finger got caught in the prop of a new build and it had a flexible slow fly prop. If it was my Advance 25 e's prop (APC 11x8 E)... I couldn't imagine the dmg it would have done.
Old 07-27-2012, 02:56 AM
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Default RE: Help with prop sizes and electric motors

G'day

I think you will find that E type props are lighter and thinner than Glo type props because glow engines give a big torque thump to the prop every second rotation for four strokes and every rotation for two strokes where as electric props give smaller torque thumps many times per rotation. As a result, the electric motor is "kinder" to the prop than an internal combustion (IC) engine is.

Electric props do tend to be very sharp but so do small IC props. The worst cut I have ever managed to give myself was with an APC 6 x 3 IC prop on a 0.8cc diesel engine. It took quite a chunk out of my finger which just brushed the end of the prop with the engine in full song. I suspect electric props will do this and better too.

The big thing with electric props is to not use one which is too large. The motor will try to turn it and draw excess current and may destroy its self and/or the ESC. I always test my motor/prop/ESC combinations with an inline AMP meter. The Turnigy 130 from HK works well and is quite cheap. I put on a prop that I think will do the job and measure its effect on the motor current draw and go smaller or larger depending on what I measure.

Cheers

Mike in Oz

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