Brushless Power Ratings... - RC Groups
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Nov 13, 2002, 12:30 PM
Yogi's Avatar

Brushless Power Ratings...

I am working to determine what prop to use for my FVK Bandit with a Hacker B40 8S on 8 cells. Several folks are using a 12x8 or 12x9 and a few a 13X8 on this motor and plane with 8 cells.

I have run each in MotoCalc and compared the calculations.

How do you know how much power a given motor will handle without problems? What is the most important figure to look at? Max Amps? Watts In? Voltage? Temperature?

Hacker seems to give absolutely NO information about the power ratings of their motors. ( at least not anywhere on the web - I haven't talked to a dealer )

What determines the power the motor can handle? What will lead to its demise? Too many amps for too long? Too high a temperature?

I have similar questions about the 27/13/4 Aveox motor in my Zagi. Most of the time, I run a 5.5X4.4 prop on 10 cells at about a 23amp static draw. This produces about a 230Watt input. I have tons of speed with this setup, but I think I would like to try something different and go for more vertical. so I would like to instead run on 8 cells with a bigger prop. I ran some numbers for this combo, and I would have to prop at a higher amp rating to get the same power input. Should I be concerned about too many amps, or a high power input.

The sticker on the motor (that has long since fallen 'melted' off )only said, 20A max. This seems like a worthless number to me without a Voltage to go with it. It should have a Max Power input rating shouldn't it? It does get HOT, and I do let it cool between runs, but I am concerned that I am killing it.

any help or suggestions/technical info would be greatly appreciated.


~~fred francis
Atlanta, GA
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Nov 13, 2002, 06:09 PM
Supersonic Engineering
GordonTarling's Avatar
Fred - the Hacker B40-8S with 4.4:1 and 8 cells with 12 x 8 prop is predicted to draw 65 Amps according to Motocalc. I'd say that this is about top limit for that motor. You MAY get away with a 12 x 9 or a 13 x 8 but I wouldn't advise it.

Temperature is what will kill the motor - 110 degrees C absolute max.

Sorry, can't advise on the Aveox setup.