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Dec 12, 2019, 05:13 AM
'Extreme Fabricator'
I was quite surprised to find the video still up on Youtube that gave me the idea for using the laser back then, as you can see, it sorts accuracy in all it's forms, and KST are even better now.
I used to fly heli's and I think that's what probably started my servo obsession around this time, 2012...

KST DS125 MG Wing Servo Laser Test.flv (2 min 7 sec)
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Dec 12, 2019, 07:28 AM
Flight school dropout
Quote:
Originally Posted by Spike Webb

Also, an update on my build:
My sunnysky x2216 880kv motors arrived. hopefully, the kv is high enough, but if not, i can go to 10 inch props. need to order some other props with different pitches for testing anyway.
Iím running 2216 900kv with 8x6 props on 4S. AUW is around 1700g and it cruises at 50% throttle, 55kph, 4.5A. Max amps is 23 on takeoff. Max speed is around 85-90kph flat and level.

A bit more power would be nice. Maybe even 9x6. Is that what youíre planning to use?
Dec 14, 2019, 03:16 AM
Registered User

more power


Quote:
Originally Posted by toypilot
Iím running 2216 900kv with 8x6 props on 4S. AUW is around 1700g and it cruises at 50% throttle, 55kph, 4.5A. Max amps is 23 on takeoff. Max speed is around 85-90kph flat and level.

A bit more power would be nice. Maybe even 9x6. Is that what youíre planning to use?
I'm planning on starting off on 9x6, but i can easiely fit 10 inch with my maxwell 1600 wing design. I have option to shift slightly on pads, and use 10 inch too. just picked up some 10X7 counter rotating Gemfans (similar to APC) to try. not sure how much my motors can take, but they are qite a bit bigger than stock, so will put on thrust test stand, check max amps/watts and check motor specs to see if it's safe to run 10's. Tehy are 880kv. i also have some higher KV motors to try, so will see. i prefer largest practical disk area for low speeds, but this plane is a bit faster than what i'm used to, so will have to test in flight for amp draw in RTL at a certain airspeed, trim_arspd in arduplane.

Thanks to Alice Cooper once again for the servo advice. ordered 6 of the Corona CS-929MG's for testing. Will advise everyone if they are good. price is right. not too cheap, not too expensive.
Dec 14, 2019, 07:41 AM
Flight school dropout
9x6 will be the way to go for you. 10 will be overpropped unless you go shallow pitch in which case you’ll lose efficiency (even if bench tests say otherwise!).
Dec 14, 2019, 12:40 PM
Registered User
PaunFD's Avatar
Would not 9x6 prop be a little bit more out of the efficiency numbers? I'm thinking that the 9x6 prop will waste quite a lot of energy by generating unnecessary thrust, and the air will leave the prop at some low speed - therefore the plane's air speed will not gonna increase ...
It is like ... torque vs horse power on a vehicle ...

So far efficiency numbers that @toypilot got for his Binary are not impressive. I mean 4,5Amp out of a 4S pack for 50kph air-speed are no way near what i would consider impressive ... in spite the fact that i know that my 62 - 66kph for 8 - 8,5Amps (at about same AUW 1721g) are also not so impressive.
On mine, i use stock power plant with stock 8x4,5 3 blades props which also generate and waste valuable power for generating tones of unnecessary thrust which plane does not need to maintain a given air-speed in either slight climb or straight and level flight. Maybe if i'l use 8x6 2 blades prop, i'll get a bit more speed for same amp draw in straight and level flight.

Maybe @Spike Webb efficiency numbers will gonna be greater, and i can't wait to see how those numbers will be!

@Toypilot, if you would have gone for a 1100KV motor with those 8x6 2 blades props of yours, your efficiency numbers would have been greater, meaning more speed for the same 4,5Amps ... or 70 or eve 80kph for like 7 to 8Amps draw ... But, i'm not sure if that would have been the case, because there are 2 motors which sums up the amp draw ...
Dec 14, 2019, 03:10 PM
Flight school dropout
This plane just isn’t as efficient as a small wing or something more streamlined. 1100kv wouldn’t make it any more efficient, it would actually make it slightly worse. 2 blade props are also more efficient than 3 so is the higher pitch. Definitely change props. Those numbers were just cruising around lots of diving and climbing. It could do better I guess..
Dec 14, 2019, 04:22 PM
Registered User
PaunFD's Avatar
Actually more kv means some more rpm in some given situations.
With 8x6 2 blades prop and 200 more rpm air should (will) live the prop at higher speed. Up to a point thrust given by the volume of air running faster will be enough to overcome the plane's overall drag to some more higher air-speed than same prop spinned by 900kv motors.

Because this plane is not so streamlined as you said, there will be a point - an air-speed where thrust generated by both motor will no longer be enough to overcome the drag ... and from that point onward motors will no longer be able to accelerate nor to sustain that air-speed and the power requirements will sky-rocket.

Those 900ov motor will feel more better with 9x7 prop ... In some other applications I've run 12x7 prop for having enough static thrust for take-off/hand-launch the plane and to enable the plane to fly/cruise at 80kph while drawing around 170Watts. Of course spinning that huge prop in WOT requires around 64Anps out of a for 4S pack - but WOT was/is used only on launch for no more than 5 seconds so the lane entered in aerodynamic controlled trajectory/flight.

Do note that my English is limited so I try to explain this phenomenon with my limited vocabulary ...
Dec 14, 2019, 06:11 PM
'Extreme Fabricator'
And, there are props and props.. some, like APC, Gemfan, Graupner and Master Airscrew can vary by as much as 20% for a given pitch. Efficiency changes at both rotating speed and speed through the air.
I've found MA stand out way ahead, but I cannot get hold of two blade in both directions. I run their three blade on my mtd which still outperform any of the other two blade makes Ive tried in total thrust, and still come close to two blade for efficiency.
I also use a 6 inch prop in lots of smaller builds and found the Emax Avan in that size is miles ahead of anything else, it has the most linear thrust line of anything, yet strangely they only make it up to 6".. if they did a full range of sizes it would wipe out the competition, as they are also almost indestructable being polycarbonate, and they're perfectly balanced.
Dec 14, 2019, 09:22 PM
Registered User
Quote:
Originally Posted by alicecooper
And, there are props and props.. some, like APC, Gemfan, Graupner and Master Airscrew can vary by as much as 20% for a given pitch. Efficiency changes at both rotating speed and speed through the air.
I've found MA stand out way ahead, but I cannot get hold of two blade in both directions. I run their three blade on my mtd which still outperform any of the other two blade makes Ive tried in total thrust, and still come close to two blade for efficiency.
I also use a 6 inch prop in lots of smaller builds and found the Emax Avan in that size is miles ahead of anything else, it has the most linear thrust line of anything, yet strangely they only make it up to 6".. if they did a full range of sizes it would wipe out the competition, as they are also almost indestructable being polycarbonate, and they're perfectly balanced.
I agree, and have had similar expeience with MA props. So far my most effecient result in larger aircraft with full instrumentation for testing has been APC 13 x 8. According to MA their 3 blade props only lose 2% eff. over 2 blade ones.
Agree that static tests have little to do with in flight eff. unless they are done in a wind tunnel... but fully instrumented aircraft is just as good.
Another factor is the mass of the prop, and it's mean distance for the hub.. especially when flyign with autopilot. Arduplane can adjust the throttle slew rate, but you don't want to go too low, as could compromise ability to control speed in certain circumstances, and result in a stall.
Dec 15, 2019, 12:42 AM
'Extreme Fabricator'
Quote:
Originally Posted by Spike Webb
I agree, and have had similar expeience with MA props. So far my most effecient result in larger aircraft with full instrumentation for testing has been APC 13 x 8. According to MA their 3 blade props only lose 2% eff. over 2 blade ones.
Agree that static tests have little to do with in flight eff. unless they are done in a wind tunnel... but fully instrumented aircraft is just as good.
Another factor is the mass of the prop, and it's mean distance for the hub.. especially when flyign with autopilot. Arduplane can adjust the throttle slew rate, but you don't want to go too low, as could compromise ability to control speed in certain circumstances, and result in a stall.
I usually add some ramping into my throttle mix, a 0.5 second delay isn't noticed in flight characteristics but it prevents overcurrent or sync problems.
I can slam the throttle and it just ramps up very smoothly.
Dec 15, 2019, 03:50 AM
Registered User
PaunFD's Avatar
Usually a 3 blades props is used when ... a 2 blades prop of bigger diameter cannot be used and motor is powerful enough for generating more thrust.
A 3 blades prop of lets say 8x6 will generate more thrust than a 2 blades props - however the efficiency and the air-speed that the 3 blade prop will achieve will be few kmh lower than the 2blades prop (assuming everything else remains identical).

For those who wants to get some general idea about some performance of a given motor + prop combo on some given lift surface/wing/plane will do, they should check out the ecalc.ch.
Ecalc.ch will give a table with various information like rpm, current, throttle, thrust Amps, and ... air-speed (evaluated) and so fourth ... values that are quite close to the real life data .... Of course those values are not "absolute values", and sometimes they can be significantly improved, or on the contrary ... but those values are some sort of a start point to one to know what should expect from a given combo ...

Here is an example ... (my example is for a T-Motor F40 V3 2600KV which i use on the little Dart 250G).
Dec 15, 2019, 08:28 AM
'Extreme Fabricator'
I need to resurrect my wind tunnel..

Well, laminar wind machine thing.
Dec 15, 2019, 04:09 PM
COFPV Addict
Starbuckin's Avatar
Quote:
Originally Posted by alicecooper
Emax Emax Emax... the good the bad and the ugly.. they are an interesting product, and I think your experience may stem from one of two problems I've seen with Emax servo's. One they seem to be frequently cloned, and second, they are often sold as factory seconds especially when purchased in bulk lots of four or more. I purchased a batch of six from Banggood, and every one had a different fault, yet every 'single' purchase unit (still many at a time) have been flawless. I believe none get thrown away from the factory, the quality rejects just get sold as bulk cheapies. I won't trust them for higher value builds anymore, despite the good ones proving very good and dependable, it's too big of a gamble for me. I had used Corona digital servo's in lots of servo size limited builds and they have been so good I'm starting to put them everywhere.
Just wanted to back you here and say I've had the exact same experience as you with Emax ES08MG II servos (I believe they are) though I bought them from a different source. My Skyhunters all run them but I bought them not in bulk. I bought a bulk of 8 and when I went to use one I had three fail one after the other in about 4 minutes of just sitting plugged up they started buzzing and fluttering around all over the place. I trust the ones in my Skyhunters but won't ever use anymore of them and was wondering what servos to get for my new Binary which I just pulled the trigger on. Thanks for chiming in about the Coronas.
Dec 15, 2019, 04:40 PM
Registered User
Papsi's Avatar
FLASH DEAL for 88€

Sonicmodell Binary 1200mm Wingspan
Dec 20, 2019, 02:16 PM
Registered User
Quote:
Originally Posted by SonicModell
HI Mate,

Yes, you won't find them on SS site, cause they only list their "own" models, not the custom production like these. Sadly are only offered with the pack. But again, you're not forced to get that pack, you can work it out with any 2212 (1000-1250kv). Those are nice, but I don't want anyone to feel forced to get stuff they already have.

30-40km is totally doable with Li-Ions... Right now we have customers doing that on a daily basis (coast patrolling).

Cheers!

Hi Friends, Any place or place where you sell the ready-made Li-ion packages?

welding is very bad for me


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