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Old Oct 05, 2012, 02:13 PM
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Chilliwack, BC Canada
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Originally Posted by Little-Acorn View Post
That's the number reported by Blaser for his plane. I hooked a WattMeter to my plane last night before swapping out the stock motor, and found it drawing 19.5A at 11.5V with a (non-stock) Turnigy 2200mAh 25C 3s battery and the stock (mis-formed) propeller. Volts times Amps =224 Watts. With an APC 9x4.5E propeller, it drew 23.2A, also at 11.5V, V*A=267W.

As always, Your Mileage May Vary.
Thanks LA. It might be a good idea to remove Blazer's power info from that Tech info and Faq page since you have proved it to be off by around 50% on the high side. It looks like he used a different motor and, without knowing what it was, that info is useless.

BTW, I don't understand why you had to go to a 3900KV motor in your SkySurfer (the smaller one) to get reasonable performance. I have a 2200KV inrunner in mine with a 30A ESC a 3S 2200 battery and get great performance with a 6x4 APC prop. It will climb vertically for quite a while before stalling and climb continuously at well over 45 degrees. Unlimited vertical, no, but it has alI I need.
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Old Oct 05, 2012, 02:33 PM
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Va.Beach VA.
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Thanks AJ, but I was just only stating that I own a pusher style plane..like this one.... http://www.hobbypeople.net/index.php...-ailerons.html
The motor mount that antennahead is a good idea. But I'm not sure if it would be good for my e-sport/superfly motor mount region. And I'm not looking to do that to my 36mm motor on my SSS. Of course I'm just going to screw it in place and use my brothers watt meter.
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Old Oct 05, 2012, 03:37 PM
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Lincoln, CA
Joined Oct 2006
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Originally Posted by G-LO View Post
Thanks AJ, but I was just only stating that I own a pusher style plane..like this one.... http://www.hobbypeople.net/index.php...-ailerons.html
The motor mount that antennahead is a good idea. But I'm not sure if it would be good for my e-sport/superfly motor mount region. And I'm not looking to do that to my 36mm motor on my SSS. Of course I'm just going to screw it in place and use my brothers watt meter.
You are welcome. I can only agree with you because I don't know anything about your Superfly (looks like a Sky Surfer-regular one). Your plan seems good to me. Using your brothers wattmeter is the sensible thing to do. If you get a little change in your pocket, I encourage you to get one of your own. They are available pretty cheap these days. The Turnigy wattmeter is as good or better than the WattsUP wattmeter and much cheaper (I have both). So, maybe on your next order to HK.........
AJ
P.S. I tried to post the link. But, HK is down right now. I will come back here later and post the link.
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Old Oct 05, 2012, 04:13 PM
Wonderfully Wicked
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Willoughby, Ohio
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Done with this thread.
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Old Oct 05, 2012, 05:20 PM
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San Diego, CA
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Originally Posted by ajbaker View Post
What were the wattmeter readings?
AJ
I don't know. The wattmeter was dedicated to e-bike use for a couple years, I only put R/C battery plugs on it a week or two ago.
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Old Oct 05, 2012, 05:24 PM
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San Diego, CA
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Originally Posted by The Don View Post
A 3900 KV motor is not intended for direct drive props. That high of KV used in a 70mm EDF will be about 1000 watts and that is direct drive but with a 2.75" diameter rotor so trying to swing a 6" prop is wasting power
Likely true. And unimportant, since I only do it rarely and then only to get out of trouble and/or watch the beastie climb like a scared cat.

Quote:
This motor calc (link below) is a nice way to virtually test setups with buying and frying parts or wasting money and time in the process. You can get about 5 lbs thrust pretty easy with motors in the 1200 range and more at 1500KV on 4S with an 9x4.5 APCE prop. This is the way to go if you want o boost power on this model.

http://www.ecalc.ch/motorcalc_e.htm?ecalc

Here is another one:
http://adamone.rchomepage.com/calc_motor.htm
Thank you, Don! Those sound VERY useful! I'll have a look when I get time, hopefully this weekend.

I assume they estimate static thrust only? Or do they also try to estimate thrust with airspeed?
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Old Oct 05, 2012, 05:32 PM
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Originally Posted by Little-Acorn View Post
That's the number reported by Blaser for his plane. I hooked a WattMeter to my plane last night before swapping out the stock motor, and found it drawing 19.5A at 11.5V with a (non-stock) Turnigy 2200mAh 25C 3s battery and the stock (mis-formed) propeller. Volts times Amps =224 Watts. With an APC 9x4.5E propeller, it drew 23.2A, also at 11.5V, V*A=267W.

As always, Your Mileage May Vary.
I just put the original stock motor back in, and put an APC 9x4.5E prop on it since both my stock props turn out to be mis-formed (the blades are not 180 degrees apart! More like 178 or so). Also left the dual plug on the 60A ESC harness, so I'll be running the two 2s 5000 mAh R/C car batteries on it in series.

With that prop, it draws 27.5A at full throttle, and one battery fell to 6.7V. I'd guess the other is doing about the same, meaning voltage to the system is probably 13.4V or very close to that at full throttle. Rather unimpressive performance from the GensAce batteries. I don't recall abusing them THAT badly in the car.I'll check RPM too, now that the sun is up. Well, it's cloudy, hopefully the optical tach won't mind.

Might also try the 8x6 3-blade EMP prop just for kicks and grins, though it might be too much for this motor (ditto for the 9x4.5 2-blade). I'll probably pick up an APC 8x6E 2-blade if an LHS has one, they seem fairly well balanced.
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Old Oct 05, 2012, 05:36 PM
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Quote:
Originally Posted by Little-Acorn View Post
That's the number reported by Blaser for his plane. I hooked a WattMeter to my plane last night before swapping out the stock motor, and found it drawing 19.5A at 11.5V with a (non-stock) Turnigy 2200mAh 25C 3s battery and the stock (mis-formed) propeller. Volts times Amps =224 Watts. With an APC 9x4.5E propeller, it drew 23.2A, also at 11.5V, V*A=267W.

As always, Your Mileage May Vary.
I just put the original stock motor back in, and put an APC 9x4.5E prop on it since both my stock props turn out to be mis-formed (the blades are not 180 degrees apart! More like 178 or so). Also left the dual plug on the 60A ESC harness, so I'll be running the two 2s 5000 mAh R/C car batteries on it in series.

With that prop, it draws 27.5A at full throttle, and one battery fell to 6.7V. I'd guess the other is doing about the same, V*A=368.5 watts. It'll probably change somewhat in the air.

Rather unimpressive performance from the GensAce batteries. I don't recall abusing them THAT badly in the car. I'll check RPM too, now that the sun is up. Well, it's cloudy, hopefully the optical tach won't mind.

Might also try the 8x6 3-blade EMP prop just for kicks and grins, though it might be too much for this motor (ditto for the 9x4.5 2-blade). I'll probably pick up an APC 8x6E 2-blade if an LHS has one, they seem fairly well balanced.

ON EDIT: The other battery maintained 7.0V, guess it's a little healthier. RPM was 12,600 with the 2-blade APC 9x4.5E prop, voltage 13.7V, V*A=376.75 Watts. That's about the RPM the SuperTigre .23 turned without a muffler on my old TriSquire with the Heathkit radio (double-deck receiver, KPS-9 servos, plane weighed a ton). So that should keep the SSS out of the weeds adequately.

With the 3-blade EMP 8x6 prop, it drew 35A at 11,650 RPM. The ESC didn't get warm, though I only had it turning that fast for 5 seconds or so. Might keep that prop on the plane for the next flight. RPM with no load at that voltage is theoretically 17,125 RPM, so it's lugging down a little. Well, I've abused motors worse. Time to go fit those two batteries in the nose (some trimming needed) and see what it does to weight&balance.
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Old Oct 05, 2012, 05:47 PM
Wonderfully Wicked
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Willoughby, Ohio
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Done with this thread.
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Last edited by The Don; Oct 10, 2012 at 09:35 PM.
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Old Oct 05, 2012, 05:50 PM
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Originally Posted by Little-Acorn View Post
I rigged the 2-connector harness on the 60A ESC's battery cables last night, to connect two LiPo batteries in series, and tried it. Now my wattmeter can read only one battery's voltage, but the current of both batteries of course since they are in series. Plugged two 4000mAh 2s LiPos (nominal 7.4V each) from an R/C car, into the harness, started slowly, and revved it up.
Sorry if you think I am picking on you but I do not think you understand what you are doing or how brushless motor power trains work. OTOH the fact that you are open to posting exactly what your have tried is a good thing, because hopefully it means that you are willing to accept suggestions and learn.

"Starting slowly" with a brushless motor ESC does nothing to limit the current going to the motor. A brushless ESC sends a string of current pulses to the motor, each one of which is the same amplitude as WOT, even at low throttle. That, combined with your inappropriate motor and prop combo, is why things are getting hot.

Pleasel get yourself a proper RC power meter and learn how to use it..
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Old Oct 05, 2012, 06:01 PM
Wonderfully Wicked
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Done with this thread.
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Old Oct 05, 2012, 07:04 PM
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Joined May 2010
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Originally Posted by The Don View Post
I don't know how many times I have seen people post on RCG that they will fly partial throttle (or program the end points on the throttle) to not exceed the amp rating of their ESC but they do not realized the amp draw on a meter is an average of the PWM duty cycle and the ESC is indeed as you say running at WOT amps just it is being pulsed based on throttle stick position.

Don
thx ever so, Don n Dave, i am also learning the electric propulsion side of life, never knew an esc is pumping full pelt but supplying throttle on demand, explains a couple of times i've screwed up in the past lol
so my question then is, i'd like to install something like a G32 but wondering what my chances are of making it work at 770kv, i thought perhaps with a 9x7 or so three blader?
i've used a Power32 on my 1900mm cessna & plan to use one on my X8 2000mm wing, cessna flew beautifully with the 32 motor but with a decent dia 2 blade prop
i'm not after blistering speed or vertical, simply a little more speed but have the reserve thrust to gain altitude at a reasonable rate... but i'm concerned i'll drain the batts prematurely burning amps
any chance of a valued opinion?
thx again for the tips, much to learn on electrickery
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Old Oct 05, 2012, 07:09 PM
Wonderfully Wicked
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Willoughby, Ohio
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770 is too low KV due to restricted diameter. I think the model is fine on the stock motor on 4S lipo instead of 3S and the Master airscrew 8 x 6 G/F series 3 prop (2blade). I still run the stock ESC (but added a BEC) and climbs out fine on this setup using a 4S 5000 lipo. I see no reason to abandon the stock motor when it is currently not being used to its potential and especially when most just want to add some extra power but not go overboard on excess power.
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Old Oct 05, 2012, 07:26 PM
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Just drove out to BH to pick up my ARF SSS. Drive there was worse than I thought.. 1.5hrs to go less than 30 miles. Once again.. thanks LA!

The pick-up was.. pleasant. Air conditioned lobby, cute girl to open up the box and show me the plane , and a freebie mini-fridge packed with drinks. Oh, and.. there may.. or may not have been an extra battery already mounted in the plane. There probably wasn't. Nope.. definitely not.

Anyway.. I know i'm repeating what counteless others have already said, but.. DAMN. IT'S GINORMOUS. The wheel on this thing would fit on yo mommas Geo Metro in a heartbeat.

Speaking of which.. everything looks to be in good working order.. except the wheel. It's attached to two plastic plates, and one of them came loose. Nothing a little glue won't fix in a hurry tho.

I was planning to maiden her in Santa Barbara at the beach this weekend, but.. screw that. I'm not waiting. If any of you are keen to check her out(or wear the second pair of goggles).. i'll be at the Balboa park/Valley Flyers RC field on Saturday(Oct 6th) around 11am.

Careful tho.. they're holding a stuka control line competition this weekend, so someone is bound to die.

I'll be the guy standing behind something, that's behind something else, that's beh....

....

....

...with a shield.
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Old Oct 05, 2012, 11:44 PM
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USA, IL, Lake Forest
Joined May 2007
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Quote:
Originally Posted by ajbaker View Post
Do you have a wattmeter? If you do, That setup would be very easy to test.
You can build a mount like my friend and I did. HERE are the links:
8. Sky Surfer Universal Motor Mount - Really nice UMM contributed by antennahead. Superb craftsmanship.
http://www.rcgroups.com/forums/showp...9&postcount=81
http://www.rcgroups.com/forums/showp...4&postcount=82
http://www.rcgroups.com/forums/showp...7&postcount=83
You would need a slightly larger coupling to accommodate a 36mm motor.
AJ
Wow, that was a long time ago, yet that plane still goes to the field almost every weekend, and despite a few crashes still looks good.
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