paulhlee

I have a newer RED Wattage Decathlon ARF, and am having trouble figuring out the power system for it. I have in my parts box the following motors:

Hacker B20/15L with 4.4:1 gearbox
AXI 2212/34 with no gearbox
Mega 16/7/7 with no gearbox

I've done some work with Motocalc, but cannot come up with anything good... I must have the wrong parameters or something. And I have lost my copy of electricalc... I'll have to dig around and find that one of these days.

I have some 3-cell 1500 Li-Po's that I plan on using - but will get a different battery if I need to. Which of these two motors will work better for this plane, and what size prop will I need? I'm looking for fairly middle-of-the-road acrobatic performance, much like the full scale decathlons are known for. I don't want any 3d stuff... just loops, rolls, etc is all that is necessary.

Thanks!

cwrr5

My Feedback: (32)

Maybe try the Hacker without the gb, maybe about a 8x6 or 7 prop to start with...? Not too sure what kinda current you'd be pulling with that - probably quite a bit.

Got a watt-meter (or similar) ?

paulhlee

Yeah I have a watt meter, but I don't think removing the gearbox is an option. It's a planetary gearbox, and if I remove it along with the pinion gear, there isn't much of a shaft to slip a prop adapter onto.

Richie

Is the Axi motor an outrunner?
If so go with that motor.
You are right about taking off the gearbox.
That motor was not designed to be run direct drive.
If you don't already have an outrunner check out the E-flite 400 outrunners.
I have the 920 kv version and it works great. It is small, light, and cheap. Under $60.
If you go with this motor go with a 9x7 or similar prop. I've used a 1500 3 cell myself and with a 11 x 4.75 it gives great vertical performance.

I hope you get it flying the way you like. I used to have a glow powered version of a Decathlon and they fly nice and look great in the air.

paulhlee

Yes the AXI is an outrunner. My concern is it is too much motor for that plane. It would probably do very well with a 9x6 prop.... but the thing would be very fast! Maybe I could cut down on the pitch to slow her down a tad....

cwrr5

My Feedback: (32)

Ah, I didn't think about that - good call on the gearbox, that doesn't sound viable. I'm not familiar with the other two motors - so ???
I would second the Eflite motors, I use several of them too(outrunner and can type). Nice for the price, haven't had any problems.

As far as speed, nothing says you have to fly full throttle all the time... [&:]

Richie

If you are worried about top speed you can always throttle back and you will get longer flight times.
You could also use the larger diameter, lower pitch prop that the motor distributor specifies. This would give great rates of climb.
Personally, I would buy like 3 props. One with the lowest recommended diameter and greatest pitch, one in the middle of the recommended diameter and pitch, and one with the largest diameter and lowest pitch. This way you can find out which one works best and have different props for different flying styles and conditions. This way you always have a back up at the field if you break one too.