Originally Posted by shanet1975
I just installed my new motor and 60a speed control in a 40 size nitro stick plane. I'm not sure what the exact motor is as I am not home. The biggest lipo I have right now is a 3s 1300. I am planning on running 4s 4000's, but haven't ordered them yet. I did try the 3s on it and it went about 1/2 way up on the throttle stick and that was all it had. Wasn't much. Will I notice mush difference between a 3s 1300 and a 4s 4000?
Don't know what brand of motor you have, but your notes indicate it weighs in at around 5 ounces. For a rough rule of thumb, anything over 100 watts per ounce of motor weight is kind of pushing the motor.
Don't know where that 98% efficiency comes from though, even the top of the line Hacker motors have trouble reaching 90%.
I used www.motocalc.com
(Free for 30 days, $39 after that) to check on things. Per www.motocalc.com
, this motor is not particularly efficient, running only about 70% efficient on 3 Lipos, and 54% efficiency on 4 Lipos, using your 10X6 prop. Because of the awful drop in efficiency, you might not notice a big difference between 3 and 4 cells.
Check out the Hacker A40-10S motor. (It weighs in at 9.4 ounces) Its winding resistance is only 7 milliohms, nearly 5 times less than your motor. Motocalc indicates on the same 10X6 prop, it will pull 38 amps out of your Lipo with three cells, for 360 watts. Bump that up to 4 Lipo cells, and this same motor will pull 63 Amps out of your Lipo for 820 Watts. Four cells will put out over 100 ounces of thrust. This gives a pitch speed of about 70 MPH, with around 12,000 RPM on the motor.
I've got seven Hacker motors, ranging from their A30 series, to a new A60-16M, rated for 10 Lipos, and around 2200 watts. All perform exactly per the Hacker specs. Most of my motors are three years old now, several of them have over 200 flights on them, with zero problems of any sort. (Nope don't work for Hacker, or motocalc, just like their stuff)
If you are not after a particularly fast model suggest you go to a Hacker A40-14S or other winds for a lower KV rating.
Other motors are also available such as the Scorpions and similar. Some of these motors are rather over rated by their (China) vendors. You can check them out in motocalc before buying anything.