I recently completed some bench and field testing on the "small but mighty" RC Timer FR2205 2550 Kv quad racing motor for use in a park jet application. Here is a picture of it as it arrived in the mail.
Given that quads and multi rotors are now such a large and fast growing part of the RC world, I started looking into some of the motors used for these as I think they are probably leading the electric RC community for technology, lightness and power.
I have been dealing with RC timer for many years, their servos are my favorite as they are very good and the least expensive around, even cheaper than Hobby King, Banggood, etc. In the last few years, they have definitely changed their focus to jump on the quad bandwagon for general use, FPV and racing, so I took a good look at many of their motors to see if I could find something that would give me the equivalent power of any of our recommended parts list motors while staying very light. Fortunately, they provide some very good charts showing thrust, amps drawn, etc with a wide range of quad style props, but at least it gave me an idea of what to expect, so I picked one up with which to experiment.
Fortunately, the bolt hole pattern on the base of the motor is identical to that of any of the motors on our parts list and it accepts the same size and thread of screws, making it easy to mount in a park jet.
Here is the bench test data using a 60A ESC with timing set to low and a freshly charged 2200 3S 40C battery for each test.
6x3 EMP/TGS prop
50% throttle - 10.5A/128.6W producing 462 gr/16.3 oz of thrust;
100% throttle - 26.4A/311W producing 880 gr/31.0 of of thrust.
RC timer 6x3x3 carbon prop
50% throttle - 9.5A/117.4W producing 400 gr/14.1 oz of thrust;
100% throttle - 29.3A/355W producing 820 gr/28.9 oz of thrust.
Master Airscrew 6x4x3 prop
50% throttle - 11.1A/136W producing 348 gr/12.3 oz of thrust;
100% throttle - 31A/359.5W producing 800 gr/28.2 oz of thrust.
Gemfan 6x4x3BN (pushes the motor on a static test beyond it's rated amps)
50% throttle - 11.8A/145.6W producing 468 gr/16.5 oz of thrust;
100% throttle - 34.8A/398.7W producing 940 gr/33.1 oz of thrust.
50% throttle - 10.9A/133.5W producing 360 gr/12.7 oz of thrust;
100% throttle - 29.4A/346.4W producing 694 gr/24.5 oz of thrust.
So all very good thrust numbers, the 6x4 APC showing the least amount of thrust, however, given it pulled amps within the motor's limits, I decided I would still field test it. I chose not to field test the Gemfan 6x4x3BN prop as in my experience they are quite loud and the wide blades create quite a bit of prop drag when it is used in a pusher/puller configuration.
As sometimes happens, the bench numbers do not always translate well to the field where the "rubber hits the road" so to speak. Bench testing is vital to ensure that prop/motor combos are not pushing the motor beyond it's specified limits and to ensure that if the prop/motor combo are good, I am using an ESC and battery that can handle the workload. After flying a series of flights testing the following props, I have arranged them in my order from favorite to least favorite based on best compromise of speed, acceleration, mid range performance (60-75% throttle where I spend about 90% of the time when flying), noise and efficiency.
- Master Airscrew 6x4x3;
- 6x4 APC;
- 6x3 EMP/TGS; and
- RC timer 6x3x3 carbon.
The 6x3 EMP did have the best "pop" when hammering the throttle, was the noisiest of the bunch and it felt like it could "use one more gear" so to speak, it never really reached the top speed I saw with the MAS 6X4X3 and 6x4 APC despite it's good bench numbers, but this is understandable as it does have less pitch.
The RC timer 6x3x3 provided the least favorable performance, decent acceleration, but slowest top end, possibly because the blades are so wide. One thing I am learning about using quad copter style props in a pusher/puller configuration is they are designed to provide a lot of lift in the vertical, but they do create a lot of drag when flipped 90 degrees.
One lesson I learned within the first couple flights was that since the motor is so short compared to most park jet motors, the prop runs very close to the leading edge of the prop slot, making a lot more noise. Fortunately, I found a couple of spacer washers in my flight box which now puts the prop about 3/8" from the prop slot leading edge and reduced the noise considerably. Also of note which I should have mentioned earlier in this post, to get correct prop clearance, I did trim about 1/4" off the trailing edge of the nacelle. You can also see that the threaded shaft accepts the bullet nut from any 3.17mm prop collet hardware which is used on the 2212 size motors.
The motor runs very cool as there are lots of vents above and below the stator and the bell being so lightweight, it does not hold the heat like other motors might. I will continue to test it's durability over the coming weeks and report back more as well as provide more flight video with the MAS 6x4x3 prop. I think it will be a great alternative motor when a person is trying to keep the weight of their plane to a minimum while maintaining good power and efficiency. I would imagine with the 6x4 APC prop, you could lighten the load even more with a 30A ESC, but with any of the other props, I would say it is safest to use a 40A ESC, but I will trial that as well over the coming weeks and report on the results.