Awhile back I had some discussion with a couple of gents from the RC Powers forum, FlybyKnight22 and Fz1Fazer on the parkjet motor bench testing thread I created a couple years ago. Both gentlemen are interested in testing and experimenting with different prop and motor combos, so we have exchanged ideas and learned from each other. In one discussion, Fz1Fazer (Andreas) mentioned he had done some preliminary testing with the D2826/6 2200 Kv motor and a 7x3 EMP prop. He was reporting thrust numbers up around 40 oz at full throttle with amp draw in the low to mid 30s. So of course this got my attention and after a bit more discussion, I ordered up some 7x3 EMP props from RC Timer and they arrived about a week ago. Here is a picture comparing one to the 6x3 EMP and 6x4 APC props.
So after balancing one which took quite a long time, probably twice as long as it takes me to balance a 6x3 EMP prop, I put one on a motor and did a quick bench test.
Here are the results using a Turnigy Plush 40A ESC (timing set to low) and freshly charged Zippy Flightmax 2200 3S 40C battery (links to both these items on our parts list).
50% throttle -
17.0 Amps/209.7 Watts producing 585 gr/20.6 oz of thrust
100% throttle -
34 Amps/407 Watts producing 38.8 oz of thrust.
Wow, this combo moves some serious air! Now of course when you look at the specs of the D2826/6 2200 Kv motor on the Hobby King website, it does indicate that 34A is the max for this motor, so throttle management will be important in the first few tests. But keeping in mind that this is a static test, amp draw in the air should be less, so I will keep an eye on how warm the motor gets after the first several flights. I wrote an article here about static versus flying amp draw if you are interested.
At first I tried it in my old test bed 220 + flight NAMC Mig-35 and after a couple of quick runs holding it in my hand, I could see the vert stabs getting buffeted pretty badly. I suspect this is not only because of the larger volume of air, but that the prop wash is now that much wider. So to be safe, I decided to put it in my Mig-35 that has been reinforced in the back end (elevons, back plate and vertical stabilizers) with carbon fibre tube and has withstood the NTM 2700 Kv motor on 4S producing about 54 oz of thrust, so I figured I would be safe :) I did have to remove about 1/4" of foam from the bottom of the nacelles to allow for prop clearance, but otherwise it fits in there OK. Here are a couple of pictures of it in the plane and showing where I needed to trim the foam.