Wookong-M on a RC-Carbon 900 mm boom

[BorisS]

but you can also ask kopterworx.com he might have some in stock and sell them, you probably get them faster !

 

[jes1111]

okay thanks a lot guys. Jes, my life has been trial and error i am addicted to it Ran the numbers in ecalc

Since i already have the motors and the bird flying the only thing i can tweak for this are the props and lipos.

4s

www.ecalc.ch/xcoptercalc_e.htm?ecal...apc_slowfly_sf&diameter=14&pitch=4.7&blades=2

5s

www.ecalc.ch/xcoptercalc_e.htm?ecal...apc_slowfly_sf&diameter=14&pitch=4.7&blades=2

The little i know i consider 5s to be good for the system and the prop size 14 4,7 also.

Thanks

Boris

Neither link to eCalc works (I think the developer needs to sort that out still), but I was able to pick the values out of the command line.

I'm perplexed. With 14x4.7 props, neither 4S nor 5S is workable. Both of them overload the controller and/or the motor. And, very significantly, they both over-speed the prop. The 14x4.7 is a SF type, so its RPM limit is 65,000/diameter (in inches) = 4,642rpm! The 5S pack would run those at over 10,000rpm on full throttle, and the 4S at nearly 9,000rpm - neither is safe. I'm sure many people ignore this limit but for a working AP ship I certainly would not: at more than double its rated speed the prop is likely to break.

With your current 12x3.8 props and 4S, you'll be hovering at 64% throttle (that's okay) and 62A (also okay), pulling 154A on full throttle (acceptable, but watch for hot wires!).

Change only the battery pack, to 5S, and now you're hovering at 47% throttle and 58A, pulling 211A at full throttle (starting to be difficult to cope with).

Any bigger prop (13" or 14") and the figures go red on eCalc - those motors are just too high kV for anything bigger than 12". In fact, I'd conclude that for that AUW they are not happy little motors at all. Your flight times are short because at 4S they are hovering at 69.9% efficiency and on 5S at 62.6% - neither figure is good, the second one is actually bad!

The figures start to look much better if you change the engines for 2814/22 units. They are much happier, running 79.8% efficiency at 5S and 80.5% at 4S. Both good figures. Your flight time increases accordingly, the total current pull drops (104A max throttle on 4S, 141A max throttle on 5S).

My conclusion: I can see why you want to change something. Unfortunately I think it should be the motors (to 2814/22) and the batteries (to 5S), not the props.

 

[BorisS]

Jess thanks for giving an understandable interpretation for the numbers. Im am not happy about the numbers but i also don't understand why the controller would over heat. I also calculated that yesterday but with every controller i choose even if i would have selected the 100A one i got a overheating warning. What should i conclude

In fact in the test flights the controller were hot, but the motors even with 14 47 props which i was able to test shortly there was no finger touch perceivable temperature change. I will also have to put this to a practical test since (dammit if the numbers are correct) have the motors ordered 4x 5s a week ago and the props 14 47 are on there way.

Looking at the recommended combos from axi, lets me wonder why they were recommended as Cinema Series motors in the first place ?

No. of Lipol Manufacturer of prop Prop size RPM Voltage [V] Current [A] Power [W] Efficiency [%]
3s APC electro 11x7" 7640 10,5 23,8 201 80
3s Aer. CAM Carb. Skl.. 12x6,5" 7440 10,5 26,1 216 79
3s Aer. CAM Carb. Pevná 12x8" 7180 10,4 28,9 235 78
3s APC electro 13x8" 6720 10,3 33,6 263 76
3s APC electro 14x7" 6440 10,2 36,4 275 74
4s Aer. Carb. Elektro 10,5x7" 9850 13,9 28,6 321 81

 

[jes1111]

Good thing you pointed me to the spec page on the Axi site - I hadn't looked before. The 2820/14 motors are not rated for 5S - so hooking them to your new batteries would be a bad idea! That's a bit of a show-stopper!

The 14x4.7SF props will, of course, "work" on your rig. At hover with 4S, all the numbers are within spec - it's full throttle that will cause over-current on the motors, close to over-current on the ESCs and over-speed on the props. But, like I said, definitely not a good idea to tempt fate that way. Fit the 5S and things will go worse, faster!

Looks like you'll need to sell those motors and invest in the (lighter/smaller/cheaper) 2814/22 units (if you want to stay with Axi).

Motor heat is rarely a problem on multirotors because they are cooled by their own prop wash. ESC heat is a danger, though. I'm thinking that your ESC heat problems may be that the ESCs simply don't like those motors. I'd keep them because they'll probably be much happier with the 2814/22 size motors.

 

[jes1111]

btw - 2814/22 motors with 5S and 12x3.8 props - figures are right on the borderline at full throttle (too close to call considering it's just a mathematical prediction). Shed a little bit of weight and you'll probably be okay - and try to avoid full throttle!

2814/22 motors won't like the 14x4.7 props at all - too high rpm for the prop, overloading the motor at 4S or 5S.

Axi don't make a suitable MR motor for the 14x4.7 - the 4120/14 (660kV) is probably the only choice and it's monstrously heavy - I think that's why Dirk has come up with the Plettenbergs.

 

[BorisS]

what else is left except the axi 2812/22 and the plettis you mentioned something last time, with a statement similar to you still have to check but they might be to good to be true ?

 

[BorisS]

by the way whats you opinion on the QuadroPower Motor QC3328 from the us boys ?

 

[jes1111]

I think those were the ones I was referring to. Still haven't read any user reports (there should be some on RCG), but if they do live up to their spec then, yes - they're a good choice. On props, Dirk is using 14"x4"E from APC - much better prop than the 14x14.7SF (higher rpm limit) - never seen them advertised, so maybe you have to get them from him. Assuming the Quadropowers are similar spec to the 2814/22 (but with higher current capability) then 6 of those, your 5S packs and 14x4E props - good combination (according to eCalc).

 

[BorisS]

ah okay i have the whole cine star bird on my radar. I looked at the different parts and the motors yesterday, had a chance to hold them in my hands and really liked it. Compared to that I had the Skylib 8 standing there. Looks amazing but damm its heavy and massiv looking !

 

[BorisS]

lets see how good this dist. ring turns out. Working with it was really easy and a clean job. I love liquid tape. Thanks to who ever recommended it. Only substance I cold start a fetish with

View attachment 992

View attachment 991

@ jes111 if you see anything wrong about the dist board don't say it bah bah dont ! I need one successful thing today ! even if its just an illusion !

 

[jes1111]

Excellent job!

I just had another thought on props:

http://www.himodel.com/rc_cat/plane.html

Xoar props (highly praised) are a rebadge/marketing variation on China-made JXF props. Lots of CW/CCW combos available - including 14x4

QC levels may not be the same as Xoar, but sandpaper is cheap, right?

 

[jes1111]

First two props on this page: http://www.himodel.com/search.php?psearch=14x4

 

[BorisS]

okay cool ordering them and will check them out. There is so much blah going on on timig of ESCs etc.

Found this http://homepage.mac.com/kmyersefo/timing/timing.htm.

Would you agree that with the setup i have at the moment normal timming is the better choice than high ?

 

[ovdt]

I love you guys! I learn something new everytime I read here!

 

[jes1111]

I'm not an expert, but "Normal" sounds good - certainly, the consequences of running too high on timing is excessive motor heat, which you don't have - so it sounds like the motors are happy with the setting you have.

 

[BorisS]

okay rebuild finished, changed Dist. ring and shielded every single cable, receiver ESCs with a CAT 7 shielding. A days work
Starting to test from tomorrow on again !

View attachment 993

 

[Dixter]

Boris... good job, it looks very clean and tucked... good luck with the tests and tuning..

 

[jes1111]

nice job! only thing I'd also do is twist the motor wires (loosely), at least until they are inside the arms and clear of everything else.

 

[BorisS]

starting to twist what do you mean with clear of everything else ?

 

[jes1111]

Well, you can twist them all the way between the ESCs and the motors, but once the bundle is inside the carbon arm, the CF will have some shielding effect itself - and anyway the wires will then be a good distance from the sensitive components in the centre.