Hex now built and flying, but want to upgrade to good quality motors.

[Pauli 336]

I have my new build Hex in the air and doing pretty much what its meant to do, which is no mean feat given the abuse it has had at my hands!

So, I'm really looking to upgrade the motors now as the motors I have are cheap Chinese made things, and I am not convinced they won't let me down. I have restricted flight to my own 1 acre property so far, with a few excursions into the neighbouring farmers fields when I have felt adventurous enough. But I am waiting until I complete my OSD additions and get more proficient with flying before attempting FPV with my goggles. I want to have a good level of confidence in the components before this machine is allowed to fly distance.
Earlier today I received my carbon 1045 props, which I bought as an upgrade. I had a minor tumble on landing and a prop dug in to the ground. Being harder than the usual plastic blade it didn't snap, but the rotor and blade detached from the stator, as the circlip retaining the driveshaft gave way. This has got me concerned about the quality of the motors, although they have been robust so far.

So, my question is, who are the motor manufacturers to consider, and who to avoid. Also what spec should I go for based on 2 things:

1, better flight time. (I can't go higher than a 10" blade which I currently use.
2, Ability to transfer to a larger frame in due course, probably a Tarot 680 with a 12" blade.

My spec as follows:

Carbon 550 Hexacopter.
1045 blades
2212 920kv chinese motors.
30A SimonK ESCs
Pixhawk FC
Neo 8m GPS
Taranis X8r and X9D combo.
Transmitter with Fat Shark antenna
2 axis gimbal and Gopro Hero 3
Few other pieces of light equipment such as 12v and 5v BEC and batt monitor.
All in about 2500g AUW with Turnigy Battery (4s 8000mah)
I also use 4s 10000mah, 4s 8000mah and 3s 5200mah

I can get between 10-18 minutes flight time depending on battery, but thats without pushing it too hard.
I would like to use a motor that is more economic and reliable if possible.

As usual any advice much appreciated.

 

[Spitfire76]

I am building a similar rig, are the motors "SunnySky X2212" or same other manufacture ?

 

[Pauli 336]

Motors are DJI copies, labelled RHD. To be honest, they seem to be quite robust and have in the main held up very well to the abuse I have given them while learning to fly. But I want to have motors that aren't as power hungry, but also capable of a larger blade size because I am using this hex as a test bed for building and learning to fly. The next setup will have the best of this build, with the motors upgraded.
These 920 kv 2212 work really well. The copter is powerful and easy to manoeuvre but I know I can do better.

 

[moonpie57108]

More economical and more reliable can be tough.

To reduce power consumption, reduce rpm (small kv number).

One problem you will run into is that a good motor for 10" isn't necessarily the best motor for 12", a motor that works well with one of the sizes could be stressed or under powered for the other size.

For brands once you start getting into the 12", I like KDE and Tiger Motor. Unless you can find them on sale, they aren't going to be cheap and if you are still crashing you may not to jump into the expensive motors yet. My current build spinning 12 inchers is a MN3508 - 580kv I believe. Big slow motor, low amp draw on 4s.

I think DJI has a 2312? in a kit that might work well to spin 10" blades around 800-950kv, I have used them before and they seem like decent motors not sure they are any better than clones but I was paying less than$20 a motor for the DJI brand.

 

[Pauli 336]

Ive run my spec through a number of spreadsheets, and my setup currently gives me a thrust ratio of 4.3:1, which I think is pretty decent?
I could go to 800KV with a 3:1 thrust ratio at 2212 size, which for mainly aerial video and photo is probably ok. However, Thats not a huge difference, and I am wondering would the extra work the battery would have to do to provide lift from the 800KV motors negate the power saving over the 920KV's? Also, what difference would I notice from say a 2212 920 kv and a 2312 920KV?

 

[moonpie57108]

Assuming you are running the same prop, the battery is going to be less strained by a 800kv motor than a 920kv motor, the lower kv will not try to spin the same size prop as fast. Too much junk into one thought that ended up being incorrect without more information, in my opinion.

Re-word not sure it is better:
What you should see when comparing a 920kv and 800kv motor specs at the same prop size is that the 920kv can produce more thrust with more amps because it is capable of spinning faster if the prop isn't over loaded. This will work well at your currently limited 10" size. At the same prop size the 800 kv motor will product less thrust but this is only a problem if you need more thrust.

But once you jump up to a 12" prop, the 920kv motor might not be rated for that much power consumption, and you would have to stick with the 10" prop or maybe an 11" prop. The slower 800kv motor will turn the 12" prop and likely do so at a higher efficiency than a 920 kv motor spinning 10" or 11" props with the same target thrust.

If you don't need 4.3 thrust ratio, and 3 is fine, the 3 should give you more flight time. You could also make this change by using the same 920kv motor but go with a less aggressive pitch to reduce max thrust to weight ratio while increasing efficiency.

My opinion of course.

 

[Pauli 336]

thanks for that, it makes sense.

 

[moonpie57108]

I don't think you would notice a difference between 2212 and 2312 same kV, 2312 should have a slight rpm lead at max throttle but also weights a little more.

The more I thought about this, the more I didn't like my response. I think you could actually get similar flight times from either motor if flown the same. The 2312 could be a little more power hungry than a 2212 but only because it is more capable of turning the bigger prop, but we are not talking a lot of difference in 22 vs 23. If you don't push it, you probably won't notice the extra draw capability. In just a hover, with the same prop and voltage, the amp draw should really be negligible.

Using an example of 885kv and 2315 965 kv
4S system using 9"x4.5
885 kV - 100% Throttle, 19.3 amps, 1440 grams thrust, 10920 rpm, 5 grams per watt efficiency
965 kv - 100% Throttle, 24.5 amps, 1650 grams thrust, 11700 rpm, 4.5 grams per watt efficiency

But if we are them at similar thrust values:
885 kV - 100% Throttle, 19.3 amps, 1440 grams thrust, 10920 rpm, 5 grams per watt efficiency
965 kv - 87.5% Throttle, 18.6 amps, 1400 grams thrust, 10620 rpm, 5 grams per watt efficiency


Where you would see an advantage is if you need more thrust from the 965kv motor because you weight is too high and your props are constrained too small. Or if you have room for bigger props:

4S system using 9x4.5"
965 kv - 75% Throttle, 12.7 amps, 1120 grams thrust, 6 grams per watt efficiency

4S system using 11"x3.7 props
885 kV - 75% Throttle, 11.4 amps, 1160 grams thrust, 7 grams per watt efficiency

Same thrust values, the slower turning bigger prop is more efficient. For me in this case, I would use the 965kv because I live in a place the wind always blows and I am happy to give up a little efficiency for better handling in the wind. If you weather is nice and want a little more time, run with the 885 kv. I have 580kv motors for my 12" rig but I have several other quads if it is windy .

 

[Pauli 336]

Thanks so much for that, I will print it off for future reference. Being in Ireland, it can get windy, but we have nice still days also. Im mainly going to be doing aerial video and photo I expect, not much interest in racing or zipping about, but there 920's do give me a solid reserve of power. I will move up to a larger frame and lower KV motors with longer props when we hit spring next year. As you say, it doesn't seem there is much real change I could benefit from at this size by changing motor, so I'll settle for what I have on the 550, and build a larger Hex as well. I posted elsewhere that I actually got decent flight times today after switching out a dodgy esc which was causing a motor to run slow. After a thorough calibration of ESCs and the Pixhawk, I got a marked improvement in handling and a knock on longer time in the air, so this Hex is starting to get sorted.

 

[JerEl]

I have my new build Hex in the air and doing pretty much what its meant to do, which is no mean feat given the abuse it has had at my hands!
So, I'm really looking to upgrade the motors now as the motors .

I'm using the HiTech Energy Propel 4108/40 Amp Motors on an Aimtroix Evo One Y6 Frame. The motors are expensive @ $80 each but I think the best quality around and lots of power to spare. This is a 630 size Y-6 frame. It might be overkill for you but they come with different KV ratings. I went with the Y-6 over a Hex because I wanted the extra motors for safety reasons but like the wider angle for the GoPro's camera and no worries about seeing prop shading in fast forward flights, especially with headwinds.

 

[ChrisRL]

Pauli, hello!
Congrats on your build!

Well, you chose wisely because a hex has mechanical redundancy so if the FC is programmed right (as well as firmware and so on) it shouldn't fall out of the sky should a motor, prop, ESC or arm fail.

I'd say keep flying. Most of the Chinese motors are so-so, there's really only the highest end motors Avroto/Monto RC, T-Motor, KDE Direct and the rest that pay this (this being QC, or quality control) any attention beyond the minimum at all, since they cater to pros and pros fly a lot more hours than rec pilots do. Of those, Monto RC is really the only outfit to be personally involved in quality control and customer support, the rest are just manufacturers. However, expect to pay for that service. Or, on the other hand, in order to gain experience, try flying yours until failure, and also fly some failure test flights (at very low altitude, with cheap props, natch) to see what happens if and when you do get a failure.

Also remember that your spares must match your originals. I'm currently flying a 650 hex with Chinese motors, but I have six on each hex and six spare sets (motor, arm, ESC, prop) sitting around in case. And I matched them all, and calibrated everything, before I did my builds, so in the event of a failure, I wouldn't have to go starting to look for matching spares, etc., because, as we all know, failures always happen at the least convenient of times

But for the moment, I'd just keep on flying, since experience and knowledge and insight gained in the air might result in different development choices further down the road, as a result of your tests flown today.