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Jun 13, 2015, 10:55 PM
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capntripps's Avatar
Jack,

I was afraid of that, being that close to the motor danger line, and am glad I cut my flying short.

This is a perfect comparison of my 2 blades, the top looks identical to what I was flying today, the bottom is the Graupner E-Prop 10x5:

http://fpvlab.com/forums/attachment....7&d=1345369394

and

http://www.readymaderc.com/store/ind...oducts_id=1313

I'll switch back to the Graupner 10x5 E-Props tomorrow for another test.

Yes, the motor is a DJI 2212/920 and I was running 3s, 2200mah.

I am still considering replacing the E300 propulsion system for something better. I read your discussions about the TBS 750K motors and am considering switching to those. I also read your arguments for rewinding them and you made good points on that.

Andy
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Jun 14, 2015, 07:22 AM
Jack
jackerbes's Avatar
Thread OP
The 10 x 3.8 prop I tested needed an input of 120W at 100% on 3S, the 10 x 4.5 would need more but not a lot more I'd think. If you were at partial throttle, 75% or so, I'd be surprised that it was too much for the motor. But the heat you found speaks for itself and cannot be denied.

The 920 Kv motors would have a no load RPM of about 12.3 x 920 or 11,316, and at the typical 75% of that at the continuous rating RPM it would be at about 8450 RPM. My testing on the 10 x 4.5 CF prop shows it needing about 200W at 8100 RPM or so and that would put your 50W motor at 4W per gram and that is a bit on the high side.

If you wanted to upsize the motors for the 10 x 4.5 props I'd look for a motor that was heavier and about the same Kv, maybe 100 or so lower. Look at how the data compares for two of the motors I test on that 10 x 4.5 CF prop:

Multimate MT2212-850 (65g)
195W
8129 RPM
725g Thrust

Multimate MT2814-750 (94g)
208W
9000 RPM
1090g Thrust

For the heavier motor you get more RPM and thrust for the same input power, about 25% more thrust in fact.

I think you just need to get the motor weight up and then you can over prop the motor a little, back off on the throttle to get down around 50% or so and that is where you'll find that better efficiency you are looking for. As an example, here is how the MT2814-750 motor does for thrust at 25% 50% 75% and 100% throttle

25% CF 10 x 4.5 14W 50g
50% CF 10x4.5 26W 120g
75% CF 10x4.5 45W 305g
100% CF 10x4.5 72W 490g

If you were flying a 1000g quad that 305g of thrust at 75% would get it up and put it in the air easily on 180W of power. And you'd undoubtedly back off a little as you flew and be somewhere below that.

Thrust to RPM and the input power needed to get the thrust is not linear at all, it is exponential. So you can see how the power curve steepens quickly as more power is needed. The often heard "I want to fly at 50% throttle" thing is not an unobtainable goal but once you tell folks that it requires more weight in the power system to do it they don't want to do that.

There is no free lunch! More power calls for more weight in motors and more duration more weight in batteries...

Jack
Jun 14, 2015, 07:44 AM
Jack
jackerbes's Avatar
Thread OP
Do you want to test four Multimate MT2814-750 motors? I will send them to you if you do.

Jack
Jun 14, 2015, 12:32 PM
Radio-Actif
capntripps's Avatar
Quote:
Originally Posted by jackerbes
Do you want to test four Multimate MT2814-750 motors? I will send them to you if you do.

Jack
Jack,

That is a lot of information, thank you. It confirms what I suspected to get that motor weight up and run at better efficiency.

I'm going to do some test flights this afternoon with the Graupner E-Props and will get back to you on the Multimate 750's. I'll PM you on that subject if you prefer.

Thank you again for the test and performance information!

Andy
Jun 14, 2015, 11:43 PM
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capntripps's Avatar
I wanted to share today's TBS Disco test flight:

The following flight was using 3s 3300mah lipos.

I flew the Graupner E-Prop 10x5's today, motor bell was ambient temp, base was just warm. I needed more throttle than the RCTimer 10x45's required for lift and to stay level, about 60%. Not very responsive during flight, slow casual was OK, but I would hate to make an emergency maneuver during rapid descent.

I then replaced the props with DJI 9443 CF's. This needed a lot of throttle to get airborne and about 70% to stay level. I also did not like the responsiveness, I had some instability at some points in flight trying to make abrupt turns where the 10x45's had no problems. I didn't feel confident taking the usual long park flight so I stayed close by just in case. The motor base was warmer, almost hot, than the flight with the Graupner E-Props.

The third flight used the soft DJI 9443 gray blades that came with the E300 system. In my opinion they were horrible, I did not feel comfortable flying them the usual long route, again staying nearby. They would defininitely not help in pulling out of a serious situation.

I believe the E300 running 3s on my TBS is just underpowered on 3s, and a bigger heavy battery exacerbates the problem. Note I am not running a gimbal, just a modest FPV system and Mobius camera. About as plain as a TBS Discovery gets.

The E300 with 9443 propellers may be a good system for a 330 size quadcopter (Phantom, etc) but to safely pull the weight of a TBS Discovery, I have my doubts.
Jun 15, 2015, 07:03 AM
Jack
jackerbes's Avatar
Thread OP
Thanks for the details, Andy.

Do you know what weight you're flying at?

I've found that if you have props that has demonstrated a combined static thrust of 1.2 to 1.4 times the AUW of the multi that will give you a quick lift, stable hover, and enough power for low energy level flight. And if you get the thrust at less than full throttle you'll also have plenty of burst power to deal with emergency needs.

Here is the testing I did to come up with the 1.2 to 1.4 theory:

Multis - Static Thrust to Flying Weight Ratio Testing - 1.2:1 is the answer! - www.rcgroups.com/forums/showthread.php?t=2186758

Jack
Nov 30, 2015, 08:21 AM
I COLLECT flyaway&lost drones!
martin555's Avatar
dear friends.

I start with the statement: I am a newbie to multirotors, I came from fixed wing GAS planes, etc, but I have been infected with the drones thing, no turning back now.

my question is about the DJI 2212/920KV motor:

please explain for me (but please be specific, no answers like "well it is just DJI")

how can this be:

DJI Flamewheel 450 frame, 4x DJI 2212/920KV motors, 4x DJI 30A esc,
NAZA M -V2, zenmuse gimbal, gopro3, FPV transmitter, iOSD, and 4 cell big , heavy 5800 lipo battery, (do not remember the props, DJI 10x3,8 maybe?) and the drone flies with no issues, 8min flighttime, 10 min economy hover time on 4S 5800 big chunk of battery

versus:

Hobbyking S500 frame, AFRO 20A esc (maybe too weak in comparison to the 30A dji mentioned before?) 4x turnigy Multistar Elite 2216 920KV motors, different props tested (okay, and no naza: just the poor KK board)

and, with small, lighter battery (3s, 4S tested) and without gimbal and fpv stuff, the hover is very hard to achieve, either it sinks or when I add just a little throttle, drone flies up)

so I know, it is not very appropriate to compare DJI 2212 motor with multistar 2216,

BUT at the looks: the 2216 is bigger than the 2212.. how can a smaller (DJI..) motor perform so well where a larger (okay.. turnigy...) motor perform so poor?

Info: I ordered 30A afros, just to try it with 4S .. but already think the multistar 2216 will be never enough for the S500.
Nov 30, 2015, 10:31 AM
Jack
jackerbes's Avatar
Thread OP
The props are the load and the most important consideration in the power train. And the props, battery voltage, and Kv rating of the motor all have to work in unison to generate the needed thrust. And of there is a mismatch in the voltage or prop size it will work poorly or maybe not work at all.

So you need to figure out what props you used and include that important information in your questions.

Jack
Nov 30, 2015, 01:16 PM
I COLLECT flyaway&lost drones!
martin555's Avatar
hello

first I tried

https://www.hobbyking.com/hobbyking/...dProduct=66283
Gemfan DJI Style Propeller 9.4x4.3
as I think this are very quiet but too thin they bend under weight, but rev well.

after that

https://www.hobbyking.com/hobbyking/...dProduct=55443
Multirotor Carbon Fiber DJI Phantom Fitting 9.4x4.3

as I think this seem "too heavy", rigorously balanced but instead pull, it only generates vibration and noise

I know they are the cheap of the cheapest but I wanted to figure out which is better the slowflyer shape, the dji shape, that thin electric shape etc.
after these I tried these
https://goo.gl/photos/9GddeJxpfvGG5uwd8

620 gr is the frame with 20A afros. without battery. add 4x60 grams for the motors.

I also purchased pro at xcoptercalc but could not figure out. but explain me why use larger motors when (okay.. DJI) 2212 flies soo well with that monster setup 4s 5800 etc!!!
Last edited by martin555; Nov 30, 2015 at 01:23 PM.
Nov 30, 2015, 02:08 PM
Jack
jackerbes's Avatar
Thread OP
Quote:
Originally Posted by martin555
hello

first I tried

https://www.hobbyking.com/hobbyking/...dProduct=66283
Gemfan DJI Style Propeller 9.4x4.3
as I think this are very quiet but too thin they bend under weight, but rev well.
If you look at the test data I posted back in post #2 those DJI 9443 plastic props showed this kind of thrust:

3S - 50% = 250g
3S - 75% = 428g

4S - 50% = 357g
4S - 75% = 705g

Quote:
after that

https://www.hobbyking.com/hobbyking/...dProduct=55443
Multirotor Carbon Fiber DJI Phantom Fitting 9.4x4.3

as I think this seem "too heavy", rigorously balanced but instead pull, it only generates vibration and noise
I also tested a CF 9443 8mm through hole hub prop that is identical to the HK props and got these kind of numbers:

3S - 50% = 263g
3S - 75% = 502g

4S - 50% = 422g
4S - 75% = 757g

Quote:
I know they are the cheap of the cheapest but I wanted to figure out which is better the slowflyer shape, the dji shape, that thin electric shape etc.
after these I tried these
https://goo.gl/photos/9GddeJxpfvGG5uwd8

620 gr is the frame with 20A afros. without battery. add 4x60 grams for the motors.

I also purchased pro at xcoptercalc but could not figure out. but explain me why use larger motors when (okay.. DJI) 2212 flies soo well with that monster setup 4s 5800 etc!!!
Those thrust numbers from static testing are a reliable predictor of the potential for lifting thrust in flying. I have found that a static thrust that is about 1.2 to 1.4 times the AUW will lift and hover nicely. So that also works out that if the lifted weight is about 71% of the static thrust it flies well. So I would give the props tested above this kind of flight potential as far as the AUW that would probably work well:

DJI plastic 9443
3S - 50% = 250g x 4 = 1000g x 71% = 710g AUW
3S - 75% = 428g x 4 = 1712g x 71% = 1216g AUW

4S - 50% = 357g x 4 = 1428g x 71% = 1014g AUW
4S - 75% = 705g x 4 = 2820g x 71% = 2002g AUW

Carbon Fiber 9443
3S - 50% = 263g x 4 = 1052g x 71% = 747g AUW
3S - 75% = 502g x 4 = 2008g x 71% = 1426g AUW

4S - 50% = 422g x 4 = 1688g x 71% = 1199g AUW
4S - 75% = 757g x 4 = 3028g x 71% = 2150g AUW

The only thing I don't see in your questions are the actual all up weights (AUW) of the various prop and battery combinations as you tested them.

As far as efficiency comparisons you can take some measure of that from the input power in Watts at the various test setting and get a rough idea as to which prop and voltage combo might be the most efficient but it is really the actual flying of it and the flight duration and recharged capacities that will really be the tell on that.

Jack
Nov 30, 2015, 02:24 PM
I COLLECT flyaway&lost drones!
martin555's Avatar
I will measure with

http://hobbyking.com/hobbyking/store...r_1_5_TFT.html
Dec 06, 2015, 08:08 AM
I COLLECT flyaway&lost drones!
martin555's Avatar
just a quick Info I had a chance to try Multistar High Capacity 4S 5200mAh
https://www.hobbyking.com/hobbyking/s...arehouse_.html
with 4S things are a lot better, plastic knockoff 9443 DJI self locking props pull way better.
but as we know the multistar has low C rating I also will try with stronger C , 4S battery and with 9450 dji prop too. (just roughly measured with Turnigy 2 in 1 Power Meter

my weight is 960 gr the frame, esc-s, 4x 2216 920 motors, KK board (for test. later it will be NAZE). so with 440 gr battery this was 1400 gr, (did not used the gimbal which would be 200gr and xiaomi yi which is 80 gr)

but..

I will try to update the ESC firmware (still not know, blheli or simonk will be better for me) but have big hopes for a better controller (NAZE) and maybe an updated ESC FW.
Dec 14, 2015, 04:58 PM
Registered User
Hello,

My quadro copter is made up of: cheap 4 x 2212 920kv DJI style shaft, S500 frame, 4 x 1145 props , 30A esc, 2axis gimbal 160gr, sj4000plus camera, 4000mah 3S lipo zippy 330gr, mini APM pro (total weight 1,5kg) can hover 12mins and some quick maneuvers, hovering at 55%. Without gimbal and camera, it can hover 15mins with gemfan 1045 props, hovering at 50%.

2212 920kv is an awesome brushless motor to have a fun with DIY drone.
Last edited by jociz; Jan 02, 2016 at 10:54 AM.
Dec 22, 2015, 05:36 PM
Registered User
One more test

Test - dji 2212 920Kv 3S - 4S and E300 vs multistar (4 min 30 sec)
Jan 02, 2016, 11:36 AM
Registered User
Hi,

Don't underestimate the capability of 2212, 920kv motor.
My test result for 2212 920kv 50% thrust :1045 gemfan (9gr) prop, 3s lipo 11.1volt, thrust 270gr , 2.5 amper
At full throttle, as I measured it, it can do 800gr thrust, 13amper.

I have built a wooden H - frame quadro copter with 2212 920kv motor , 1045 props, 5200mAh 3s LiPo weight of frame: 160gr, total weight without battery: 710gr
hovering flight time with 5200mAh: 25mins
Last edited by jociz; Jan 02, 2016 at 05:44 PM.


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