IFlySlowPlanes

Greetings Sal!

I have a GWS Tiger Moth that suffered some damage in a crash, so I decided to use the repair as an excuse to convert it from the standard 400 bruushed, geared motor to a brushless setup. I was hoping to use an Uberall Nippy Black 1608/160 that I picked up online for a great price. First of all, is this motor going to be compatible with this airplane? Secondly, if it is, what size prop and what capacity lipo battery would you recommend? I'm guessing this motor won't need to pull more than 20 amps? I've tried running this through MotoCalc and can't seem to get a combination that the program thinks will be acceptable. Ideally I'd like docile to somewhat sporty performance (but nothing too out of character for a Tiger moth), and long run times. Can you help me make sense of all this?

Thanks!

Dave

salnsp

The Nippy 1608/160 is not an ideal motor for this situation. The Kv is too high. I would look for a motor with a Kv of 800-1000. The Kv of the Nippy 1608/160 is 1620. Like all from this manufacturer they are not especially efficient motors.
Still, If you must use it, this is what you can do.

On a cell cell Li-Poly based on 1000 mah:

draw: 18.4 amps
thrust: 30 ounces
prop: 7 x 4 apc
prop speed: 41 mph
This will work but the low end torque suffers a bit due to the smaller prop.

Below. in this example we are using a larger low pitch prop so we can maximize thrust at lower speeds. We also see a greater amount of thrust due to the larger, more efficient prop.

Hacker: A20-20L
Draw: 18.5 amps
Thrust: 37 ounces
Prop: 10 x 4.7
prop speed: 38 mph

IFlySlowPlanes

Thanks Sal! That was just the kind of advice i was hoping for! You're a godsend!

Dave

salnsp

No Problem!