Electric Conversion Help

[Noob]

Hello,

I am fairly new to the hobby. I have been flying for about a year and a half, mostly all the Flite Test planes. I feel that I am ready and want to move up to a little bigger planes. I secured a balsa plane from a relative and want to convert it to electric but am stuck on what motor and ESC combo to get for it. The plane is 612g with nothing in it except the servos that came with it. Below are some pictures. Any recommendations would be great!











This is the motor I took off of the plane.

 

[stay-fun]

Seems like the stronger power setups of FT planes would fit just fine!

 

[Craftydan]

Threre are Rules of Thumb (RoT) for glow->electric watt conversions . . . but I dont' have the background to ID that motor at a glance, so . . .

Going by the 100W/lb RoT, and assuming the battery, ESC and motor bring the All Up Weight to 1000g (3s2200 = 200g, ESC + Motor ~100g, 100g of fudge room) you're looking at needing 200-250W of power. From the clearance, your LG have limited you to < 12" prop, and probably < 10". Again, can't tell at a glance what the original prop diameter was, but probably a good range to shoot for.

I'd look for 3S capable motors, which can efficently draw 20-25A. Prop size will set the KV -- I'd wager the 1300kv region will want a 9" prop, 1500kv a 8" prop, 1700kv a 7" prop (for that wattage on 3S). Pick your prop, go look at the motors by kv and wattage, then look at the props they recommend.

For the battery, I'd go for one of the more popular sizes -- 3s2200. 15c is enough, but might want to look at getting 20-30c if you plan to keep flying things a little bigger/faster/stronger.

For the ESC, size it to the motor. If max draw from the motor is 30A, go about 10% higher -- 33 will do, but the nearest size you'll find is 35-40A. If the motor's max draw is less, you can safely pick a smaller ESC.

 

[Noob]

The motor in the picture I believe is a .049 cox engine with a 6 x 4 prop on it. I think a 7" prop would be the largest I can swing on this plane. Based on your comments Craftydan I am thinking about this motor: http://www.hobbyking.com/hobbyking/...p_Drive_28_36_1800KV_438W_USA_Warehouse_.html

Any thoughts? is this to much motor?

 

[Craftydan]

A little heavy, but if it fits the mount and you can get it to balance, a 7" prop should do well, with a 30-35A ESC. A slow 6" is drawing 16A, so I imagine stepping up an inch in prop should get you in the neighborhood for power, and still stay under the 30A limit for the motor.

I will say I've become a skeptic of NTMs -- their smaller 28mm motors have declined in reliability recently over bearing issues -- first set I bought were great, the second not bad, the third had crap bearings. beyond that, the windings, stator and rotor are fairly well built. For your airframe it won't matter as much as a multirotor. I also keep hearing poeple with larger fixed wings are pleased with the bigger NTMs, so not sure if it's limited to smaller motors or not. As always, Caveat emptor.

 

[Noob]

I seem to be having a hard time finding something other than NTM in the 1700 - 1800 KV range that will fit. Do you think this would be a better option being a bigger NTM? http://www.hobbyking.com/hobbyking/..._Series_35_36A_1800Kv_875w_US_Warehouse_.html

I thought it was a little over kill with the 875w.

 

[Craftydan]

Wow, that's a Hoss of a motor . . .

and 120g too!

Since you're shooting for a small prop, try this one on for size:

http://www.hobbyking.com/hobbyking/store/__12919__D2826_6_2200kv_Outrunner_Motor.html

Ed from Experimental Airlines calls it a "pocket rocket", and his test data looks pretty nice -- look in the vid's description for his test data.

 

[Noob]

Thank you for your help! I think I will give that motor a try.

 

[whiskeyjack]

That little motor is a good choice. I have a number of them and no problems so far. They will swing an APC 6x4 up to nearly 2200kv. You can even go 7x4 MAS (I have a RC Powers F22 on that set up) and as long as I keep my power settings moderate the ESC and motor only get warm.
Personally I went for the Turnigy AE45 ESC but I think a 40A ESC would do fine since that motor will draw 32A WOT. Try to keep the model as light as possible and use the smallest battery you can to balance the plane. Once you have flown it a few times then slowly increase your battery mah, re-balance each time you increase, until you get a decent flight time.
Good luck Noob and make sure you share a video. WJ.