Brushless KDA Motor – Enjoy in RC Model!

I bought a new brushless motor for my FlatOut Extra 300S a couple of weeks ago from www.unitedhobbies.com (aka, Hobby City) and got a chance to install it last night. The motor is the KDA20-28M as manufactured by KDA in China. It is suppose to be a knockoff of the more expensive, more popular Hacker A20 M series BL motors. I won’t go into whether or not I believe the German-branded-China-made Hacker is any better than the China-branded-China-made KDA motor, but in just doing a visual comparison of the two motors, they are virtually identical, with the exception of the signature purple anodized housing on the Hacker vs. the blue housing on the KDA motor. For only $16, I thought it was worth taking on a shot, especially for my cheap $20 FlatOut. The Hacker A20-26M motor by comparison is almost 4x the cost, selling for $55 at my local hobby shop. Note that Hacker doesn’t make a 28-turn wind of this motor, they have the 26M which produces a kV of 1150 and the 30M which produces a kV of 980. The KDA20-28M from KDA (also called the KA20-28M) sits nicely in the middle with a kV of 1050, just perfect for the 300S I weighed it and it weighs just about 43 grams +/- 1 gram based on my scale. It’s recommended for planes from 7 – 12 oz. and draws about 12A continuous current (15A max) for a rated power output of about 120-150W with a 3S lipo. After getting it installed in my FlatOut, the plane now weighs about 9 oz. which gives me about 213W per pound. For 3D planes its recommended that you have 150-200W/lb. in order to perform all the necessary crazy maneuvers one might desire. So this new motor should be awesome. I also bought a TowerPro n18A ESC for $10.

The KDA20-28M comes with all the needed hardware to get it installed. I bought a sheet of 3/32″ plywood and fabricated a simple firewall after the firewall that came with my 300S. I traced it with a pen and cut it out with my Dremel. It’s not pretty, but it gets the job done. I glued it to the plane with 6-minute Epoxy and let it sit for a half hour. Installing the motor is a breeze at this point. I put some Loctite on the threads of the M3 screws that hold the metal adapter to the motor and then screwed it into my newly-fashioned firewall with some 4-40 x 1/2″ wood screws. These screws were a little longer than I needed and they stick out the back of the firewall, but I couldn’t find any 1/4″ long screws, so that’s what I got. I bought an APC 9×3.8 prop to go along with the new motor, which is the prop that Great Planes recommends for use with their recommended BL setup. Though I didn’t get the RimFire motor they recommend, the specs on the KDA motor are about the same, so I figured that the 9×3.8 prop would be a good place to start. HobbyCity says the motor can be used with a 9×4.7 prop without any issues, but I wanted to try out the 3.8 pitch prop first. APC provides 2 hubs with this prop for a total of 3 hub diameter mounting options. The KDA motor comes with 2 adapters to mount 3 possible hub diameters as well. Of course none of them match up perfectly, but I did manage to get the largest adapter to fit straight into the precision hole in the prop with just a tap with a hammer and after slightly reaming out the hole with an Exacto blade. It actually fits quite nicely and after getting the motor fired up and running, there is zero vibration, so it’s mounted nice and true. That’s more than I can say for trying to get a different APC prop to mount to my E-Flite Park 480 motor on my Brio 10 which still wobbles and vibrates at half throttle. These guys need to come to some sort of consensus on what size hub/adapter to use and just stick with it. But the biggest adapter fits nicely into the precision hole of the APC prop, and if/when I need to remove it, I can just pop it back out with a hammer.

After doing some static tests last night, it feels like it’s got a lot of thrust and moves quite a bit of air. The TowerPro ESC is a pain to program, I have no idea what it thinks it’s doing, but I can’t seem to figure out how to program it and the beeps and honks are so stinking loud. Most people complain about the sensitivity of these ESC’s and without adjusting anything on your radio, I can see that as being a common complaint. The ESC seems to have only three speeds, slow, medium and fast, and it only uses about 3 clicks of the available 20 clicks of range in the throttle stick. After messing around with the EPA and trim on the throttle (something I usually never mess with) I have managed to get much more usable range out of the ESC and can run it nice and slow with only a few clicks up on the stick, and then full throttle is all the way at the top. I need to mess with it a bit more to fine tune it though. Otherwise I think the ESC should work fine. Other than the impossible-to-understand manual written entirely in broken English, hence the title of this blog: Brushless Motor – Enjoy in RC Model. This is printed on the packaging for the motor. Though it sort of makes sense, I hope I do enjoy this motor in my RC model, it just sounds a bit funny and is pretty typical of products sourced straight from China without a major brand name attached to it.

It was too windy this morning to take the 300S out for a spin, but by the afternoon the wind had settled down to just a slight breeze so I got a chance to try out the new motor. I also got my wife to tape the flight so I got some video to share. I’ve stated it before and I’ll say it again, I am totally new to the whole 3D flying thing, so there isn’t a whole lot of fancy flying in the video, and I usually keep it nice and high in the sky, but it’s not too bad and shows a little bit what this plane can do with the new motor. So far I really like the new KDA motor, it pulls nice and strong and doesn’t drain the batter as fast as the stock brushed motor did. The plane flies quiet and smooth and the motor, ESC and battery are not even warm the touch after almost 10 minutes of flying. Which means I could probably go up notch on the prop and get a bit more power, which I think I might do. It still feels like it needs just a bit more umph or more punch-out from vertical, though most of my flying around is easily done at half or less throttle. Otherwise I think it’s going to work out as a great (not to mention extremely affordable) power option for any of the FlatOut planes.

Anyway, check out the pictures below and you can either watch the YouTube video below or click on the following link for a higher resolution version that will open separately in Windows Media Player.

Great Planes Extra 300S with KA20-28M BL Motor Video (640×480, 26.8MB, 4:47)