Joel Ryan

Most efficient easystar motor?

Hey guys, I'm trying to decide what motor to purchase for my new easystar. At first I was thinking outrunner because they are generally cheaper and lighter weight. However, I want to have the most efficient setup possible to extend flight time as much as possible. I don't really care about having insane speed capabilities, or amazing climb rates, just efficiency. The easystar (for obvious reasons) needs a small prop, so why use an outrunner motor, when outrunners are meant to be high torque motors?

So bottom line, which do you think is more efficient for the easystar, outrunner or inrunner? What size would be best for just general, high efficiency cruising?

And in terms of a prop, I've heard that 7x5 props cut down to 6x5 are really good, has anyone tried this?

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Krzysztof BosakPermalink Reply by Krzysztof Bosak on February 21, 2010 at 1:05am
There are 3 things to remember:
1. For high climb, outrunners are lighter to the power output, but needs large propeller
2. For endurance, inrunners tend to be better, also for smaller propellers
3. For hand launch, you use 3-4 times as much power as for horizontal flight. Therefore even moderately efficient motor is completely unreliable for hand launching.
A conclusion is the search for 'efficient motor' are not searches for any kind of efficient motor at all, just asking 'what is your completely inefficient compromise taking into account operational conditions'

Because the efficiency boils down to windspeed and hand toss force, the answers will vary wildly.
Dennis BrownPermalink Reply by Dennis Brown on February 23, 2010 at 3:46pm
Would a 7.2v 2S lipo setup be enough to get a fully laden UAV/FPV EasyStar into the air? A 4200 mAh 7.2v 2S battery should last considerably longer than a 4200 mAh 11.1v 3S, right? Would there be enough power to weight? I don't know. I am still purchasing all of my gear for my EasyStar UAV so I am at a crossroads as well regarding the power setup.
Krzysztof BosakPermalink Reply by Krzysztof Bosak on February 23, 2010 at 3:52pm
The biggest limitation of EasyStar is prop diameter. This requires fast spin, what is better achieved with high voltage. 3S is really more efficient here, 2S will not be enough without custom motor mount and larger prop diameter. Bad luck is that large thrust with small prop is achieved with huge RPM, which ends at very high optimal airspeed (some 75km/h while the airframe likes 40km/h glide).
Bottom line, EasyUAV layout imposes tremendous propeller efficiency limitations rewarded by best-on-the-market camera placement.
Chris AndersonPermalink Reply by Chris Anderson on February 23, 2010 at 4:20pm
What do you think of three-blade vs two-blade props? Three-blade can get more pitch for the same diameter.
Krzysztof BosakPermalink Reply by Krzysztof Bosak on February 23, 2010 at 5:07pm
tested both and got... consistent results in T3-3 with my best 3 blade vs 2 blade, the latter being more efficient in endurance and less efficient in cumulative climb, but all by 5%.
made 8 trials, including multiclimb and 1h+ loiters.
Mu conclusion is that 2-blade is more efficient, with proper tuning it would surpass 3-blade also in climb.
The sound of 3-blades is more 'whoshh' than 'whizz' and I like it. Availability in stores suffers, transport more difficult (not flat, prone to damage).
Tim McMahanPermalink Reply by Tim McMahan on February 23, 2010 at 6:43pm
While watching some discovery channel something or other, I had heard that more blades give you more power overall, but for true efficiency, you go with ONE blade. Apparently the airswirls from the first blade cause an inefficient airstream for the next blade to go through. Everyone wants power though, so you usually go with 2 or more, as 2 blades is like 1.5 times the thrust. My flight buddy and I tried messing around with it (EVERYBODY has broken props) and the big bummer was trying to get it balanced.

http://www.flyinggiants.com/forums/showthread.php?t=10595
Krzysztof BosakPermalink Reply by Krzysztof Bosak on February 24, 2010 at 1:40am
"but for true efficiency, you go with ONE blade"
The counterweight creates so much drag it is never worth the effort unless the prop must be folding.
PLS better understand the true target audience of Discovery Channel.
The less blades the better, but 2 blades is THE ONLY working minimum.
Riccardo KueblerPermalink Reply by Riccardo Kuebler on February 23, 2010 at 11:10pm
Hi,

to be a little concrete my setup for an EZ* uses a Hyperion Y22-L 2840 (mounted in a Speed400 case to fit the original motor bay), with a 3300mAh 2S lipo.
Propeller is a Cam-Slim 5x4.

It works well enough even in medium windy condition, say 5-7m/sec.

Of coarse (speed) performance are not impressive, but better that the original Speed400. I think this is what you expect.

You can see an FPV flight with it (catching by video my little son Trojan) here, and have an idea of the general flight characteristics and speed.

Average autonomous flight time is 20', with a good reserve. Anyway there are outrunner that drive small propeller at high speed too.

Best regards,

Ric
jasonshortPermalink Reply by jasonshort on February 23, 2010 at 11:41pm
I've been using a LiftFlight RC ARC motor (ARC-28-37-4) with a 3 blade 6x4 prop. With a new 2100mah battery and just a radio I can get about 30 min flight time. With wind, weight, extra electronics that can go down. If you want long flight times, try slope soaring. I could fly all day on just one battery with an EZstar on the right hill.
Jason
Krzysztof BosakPermalink Reply by Krzysztof Bosak on February 24, 2010 at 1:41am
BTW 3-blades are better airbrakes, so might afford shorter touchdown with prop brake off.
Riccardo KueblerPermalink Reply by Riccardo Kuebler on February 24, 2010 at 1:53am
In fact 4 blades propeller were used in F3A pattern for braking the plane when diving, to have the most constant speed.

Anyway there is a great project from a german guy with a one blade propeller in a big RC glider, but this was mainly to have smaller folding turret bay. It seems to be very effective. If I will be able to find the link I will post it.

Ric
Pawlenko MichaelPermalink Reply by Pawlenko Michael on February 24, 2010 at 9:39am
Hi Ric,

Maybe you mean this link, Florian Schambeck's website.
target="_blank">http://www.klapptriebwerk.de/produkte/antriebe/aft19/?lang=en


A 1 blade propeller gives more efficiency compared to a 4-blade one. However the last one gives more torque on lower rpm. The more blades, the lower the noiselevel.

I use Florian Schambeck's AFT-19 system in my HKM ASW-28 glider (wingspan 7.20m - 23 kilo weight).
.
My vario shows me a lift of 5 meters / sec.




Michael

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