What? T-Motor F80 (2208 2100kv Mini Quad Motors).
How? Selected to Beta test by HobbyRC.
I'd like to actually prefix this by thanking HobbyRC for giving me the chance to test them - I had heard of a few people getting their hands on them (various sizes - F40's and F80's), and so certainly liked to try them myself.
I used to run the T-Motor MN2206 2000kv back at the start of the year, but sadly I had the same issue as many others - magnets slipping. I fixed this by re-gluing them but sadly they still performed pretty badly (after a bearing replacement too I must add), so they are sat in the cupboard gathering dust. It was because of this I really wanted to get some to test - I already had a background as to what previous motors have been like so I figured I could provide a good review to those who are interested in them.
Here's some "production" shots I took :) I think they came out pretty well considering my homemade setup.
So, as you can see from the photos above - they look really well made; the motor casing is solid and looks like they will survive a crash very well - something of which I think is very important as many of us are pushing their quads to the limits 100% of the time, and having a reliable quad is quite tough. The packaging is very nice, a good plastic case and some foam inside securing the motors without any risk of transport damage, and in a small packet inside contains some M3x5mm (I think, maybe 6mm) hex bolts for attaching the motors to your normal 3mm thick arms.
Quite a heavy motor right? The specs list them as around 45g each (presumably before the motor wires are cut, they were quite a lot longer to start with) - all 4 motors will weigh more than my 180mm quad!! This was a little bit of a concern, but we all know 2208 provides a huge amount of power when paired with the right propeller and lipo, so this may not make that much difference in flight. It'll still have a crazy thrust to weight ratio >:-)
The choice of quad was a simple one - my TSX250. I used this quad primarily for filming, racing, and general flying. It's a strong and lightweight frame so the perfect candidate for the motors. As we can see above, the quad weighs a very respective 420g with everything except GoPro and Lipo. This is actually a pretty good weight, if it had been on my ZMR, we'd be looking at another 100 grams - pushing into crazy weights that are the same for quads WITH lipos and GoPros already attached!
A nice side shot here showing off the height of the motor paired with the HQProp 6045 - an easy choice - it's a slightly higher KV than my old 2206, but being a 2208 size it should pick up much faster (more torque) with the bigger stator - so it will have no problems running 6045 on 4s. I have read reports that the motor should run up to 6s even, so this setup will not even particularly test the limits, but it will however suit a 250-size quad and my purposes very well.
So, here comes my disappointment. It was all good up until now right? I mean the quad was a little heavier than the 2204 2300kv motors (around 80g), but I'd also be running high pitch propellers to make up for that. Anyway, I loaded up the latest version of Betaflight (I believe this was 2.1.5 at the time), and set off testing and tuning. I was faced with 25mph winds at the time, but as we know Betaflight tends to just work. The default PIDs are usually great, or need very minor adjustments, and then you are good. Fly away, make awesome videos, and that's it! Sadly for these, it wasn't the case.
From the moment I took off, it just didn't feel right - huge vibrations showing up through the FPV camera - which I put down to PIDs at first and the fact it was rather wind accentuating the problem. However, after tweaking them nothing had changed. I did notice on full throttle they actually flew ok (no TPA on Rewrite controller), but low down throttle was horrendous - as if a motor casing was bent around 10 degrees!
Upon further research I thought it could be down to motor timings (thanks Tom Stanton) - I was currently running med-high timing and demag set to off on my RG20 ESC's, so spent a little bit of time trying various combinations that would suit a 2100kv motor (medium and medium-low timing should both be ok as it's not a particularly high kv motor) - however nothing made any difference here. I used a few lipos through each tuning period again and I was still left with the same issues. By this time a few weeks had passed and we did have a few days without as much wind so I knew there wasn't any "natural causes" of it flying weird so to speak.
With 2 weeks passed, and actually getting a bit down about a quad with lots of issues (and having good weather for a change but not being able to make any videos!!), I decided to switch back to my old motors just to rule out that it wasn't the ESC's playing up - even on the new BLHeli settings it flew perfect out the box. I did inspect the motors again and noticed one of them looked slightly different, and all of them do not have particularly good gyro readings when spun up without props in the Cleanflight GUI, so can only put it down to huge vibrations. The one odd looking one in question does certainly seem to have a bent bell, you can see it when you rotate the casing and compare to the motor base. Being test motors, there is sadly no chance of being able to test that it was indeed just this one motor, or perhaps all of them in combination resonating at different times throughout the throttle range.
So, for me, a slightly frustrating Beta test, of which I don't even have any good videos to show off for the product. I came in with mixed feelings, and it ended up being a bit of a roller-coaster, and ended on a bit of a sad note. I know other people (Tom Smith) had found other faults with the motors, such as the bottom casing only being a "press fit" to the stator - and his motors actually came apart after a relatively light crash. Not exactly ideal.
Where do we go from here?
Well, that's a good question. I'm back on my Le Todar 2204 2300kv motors - super cheap (£4.40 posted each from China), and it flies amazing. They probably don't have as much power as the Cobra alternative, but for the cost you really can't beat it. I do know T-Motor are producing some more units based off of feedback by testing, so I'm hoping that some of the issues found are fixed, and if I get to test any again it would be great to compare my experience to see if the result is the same.