Hacker B40-5l - RC Groups
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Oct 29, 2011, 01:13 AM
Registered User

Hacker B40-5l

I just acquired a hacker B40-5L 4.4:1 motor (Kv 6720, Io 3.82, .0044 Ohms).
I can't find a lot of info on the motor, I think it may have been originally intended as a 7 cell motor (pre-lipo). I would like to put it in a free flight model and the actual motor run would be 10 sec. + a couple of seconds to get it launched.

The questions:

Would it be safe to run it on a 3S lipo? I ran the 3S numbers on the calculator on the Neumotor site and came up with the following: 10/6 folder, 85.12A, Watts in about 760, motor rpm 62985, 91.5% eff. The caution that came up: "motor voltage close to limit, check motor case temp".

The generic "instruction sheet B20,B40,B50" (It didn't list this specific motor) that came in the box lists the max. RPM as 60-80K, would the near 63000 be too high? would 12-13 seconds at this power level be OK? Would 3S be too much? I'd like to run 3S due to the lower amps and smaller prop (Large highly powered props can sometimes be problematic trim wise on a free flight)

Any comments would be greatly appreciated.

Thanks, John
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Oct 29, 2011, 04:00 PM
Registered User
I think this motor is best on 2S. There is a 2S F5B class for which it would be fine. The temperature and no load current would be too high on 3S I fear.

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