C-47 Building tips. - Page 3 - RC Groups
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Aug 11, 2004, 09:04 PM
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Hovertime's Avatar
On prop adapters-I used 2mm ones, how about you guys?
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Aug 11, 2004, 09:09 PM
know it all
I'm using the 300h motor, ecalc says 13.4A, 14.6k rpm.. all I can think is the motors overheated and demagnetized.. thus you see the high current. Did the motors get real hot at any time?

Herm

Quote:
Originally Posted by Hovertime
Another thought-maybe I got wrong motors?
More numbers 7.2V 16.8A 15800rpm.
(motocalc prediction: 7.3V 12.9A 14000 RPM) What motor do you use in ecalc?
Aug 11, 2004, 09:19 PM
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Hovertime's Avatar
Herm-thats one possibility, but they were drawing that much right from the beginning, and never got so hot it would burn fingers...
Maybe lower quality magnet batch?
However I'm not worried about that a bit, I just have to find battery that works for me.
Aug 11, 2004, 10:01 PM
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My current measurements are not that strange since people report 15, 16 A WOT with 2S lipos, which would give about 6.6V at that load... https://www.rcgroups.com/forums/show...6&postcount=64
Aug 12, 2004, 06:30 AM
Registered User
Quote:
Originally Posted by Hovertime
According to my amp draw measurements I estimate 3S lipo amp draw way above 20A. (with capable cells of course)

Please also note that my motors got very hot with 8 cell AA pack, after it consumed only 200 mAh at WOT and voltage under load of 7.7-8V and amp draw 17-18A.
When building the evatuation beta kit for GWS/Flying Models Mag. I first used the recommended GWS 8 cell 730mAh NiMi pack and was very disapointed in it's, at best, 1 1/2 min. flight time; Plus motors and ESC got just too hot! If it were not for availability of Lipos, I would have had to use a heavier 7 cell 1100mAh AA NiMi pack. I chose to use the Kokam 2S2P 2400 mAh for it's ability to deliver the required amp draw and for lighter weight. After many flights I can see that the heavier NiMi cells would not be a problem for the power available from the 300H motors to fly the DC-3.

I feel that a 2S Lipo of at least 2000mAh is ideal for this aircraft. Power management is important, but since the DC-3 flys so well at 1/2 power, this is not a problem. Either a 2S 7.4V Lipo, or a 7 cell 8.4V NiMi will allow cooler operation of your motors and ESC.

This aircraft (20-21 ounces OAW) with a 2S lipo is a rocket ship! I can't understand the use of a 3S Lipos with the stock motors.
Aug 12, 2004, 06:50 AM
Registered User
Quote:
Originally Posted by hermperez
that sounds better David, ecalc predicts 11.4Amps at that voltage setting..how does the airplane perform at that power level?

Herm
Not knowing what the actual amp draw might be in flight, full power with 2S lipos yields an incredable amount of speed. At 3/4 Tx stick/power, you can sustain inverted flight circuits. For the sake of my equipment I fly mostly at 1/2 power during 5 minute flights. Best performance is during the first 5 minutes and the next two 5 minute flights are a bit less. If I manage my power, I can just get 4, 5 minute flights with 5 minute, radio on, rest periods between flights.
Aug 12, 2004, 07:21 AM
Registered User
Quote:
Originally Posted by Hovertime
I just checked props, and yes they are 5x3 (GWS EP50x30)
Motor turn very freely, no binding.
Wattmeters are not very precise instruments at low loads like these....
Also another explanation is that your lipos are pulsing voltage at a very high rate, (ripple current) and are outputting effective voltage lover than the average that watt meter shows. Round cells voltage is stable. Also-you may be not getting full throttle? Or high resistance wires/plugs? Whats your field elevation? temperature?
Anyways our results are not that far from each other , and still far from GWS charts.
Boy, you got a busy thread going here!

I agree with you about the not so precise readings from the Wattmeter.

And don't get so techie with me, I don't know anything sept wat works! What's round cell voltage anyway? I don't even understand the use of watts, and I don't want an explination! I like Amps! I bought a Wattmeter so I could read watts in case somebody else wanted to know. I do like the Whattmeter, it keeps me safe! And I don't need a USB port.

How far is Chicago from NJ, probably more than an hour......I'll bring my DC-3 over and then I can say, Here, look. Now fly it! With rudder.

My DC-3 works, I want yours to work!!! If I had 2 extra 300H motors, I'd send em to ya.
Aug 12, 2004, 09:34 AM
Alphabandaid
I measured my WOT last night at 13 amps with the stock 5x3 props. WAs going to use the Vario three blade 6 inch, but at minimum pitch I was pulling 19 amps! PUt the stock blades on and felt a lot more comfortabel with the power and amp draw. Now if the bloody wind would die down!
Aug 12, 2004, 05:29 PM
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Hovertime's Avatar
Quote:
Originally Posted by conder53
For the first time i stuck the fuse together using gws glue, spread it on both sides let it dry for about ten minutes and stick them together, no rubber bands , no sticky tape it worked great. Make sure you line it up well, once you push it together no second go.
THAT WAS THE BEST ADVICE ,THANKS!!!
I was putting this gluing off as long as I could, having tried GWS glue(without drying if first ) and epoxy ...
Last night I put it together, using your advice, that was so easy and precise, fantastic!!! thanks again!

David, thanks, I think I'll be fine. My poor batteries BTW I used 8 cells only to measure current, I think I'll go with 6-7 AA, only problem with 6 cells at those high amps it gets to LVC (5V) pretty fast, and lower option for Pixie20P is "NO LVC" , that makes it possible to loose radio due to low voltage....
Now how do I cram 7 AA cell in this thing? I'm thinking-6 flat and one on top?
.._..
IIIIII something like that? Anyone has recommendations on strong AA's? Best that I know are 1400 CBP/KAN....
Aug 13, 2004, 01:22 PM
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Hovertime's Avatar
Have tried Pixie with LVC disabled-wanted to test at what point Berg receiver stops working due to too low Voltage.
And what do you think-it went bellow 3V, at that point watt meter went to sleep, and motors continued to run, slower and slower, until Pixie brain went to sleep , and I still had control over servos until motors stopped and voltage came back up again.
Similar results with older GWS 4P receiver, but it got brain shutdown before Pixie, a Volt or so higher than Berg. I imagine results would be a lot different with 4PII.
Aug 14, 2004, 01:23 AM
Always right
Hovertime's Avatar
Another building tip:
I have used Du-bro "small nylon hinges" instead of GWS paper ones.
Not sure if this is needed though....
Aug 14, 2004, 04:26 PM
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Hovertime's Avatar
My motors have these markings engraved:
RK-370SD-4045
TN094329
There may be other letters covered under motor mount.
Aug 15, 2004, 12:21 AM
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Hovertime's Avatar
Found a way to fit 7 AA cells .
Only one problem - they would not go through battery bay door.
And pack would look funny
But its doable.
However GP1100 is a winner for this airplane, if you don't go lipo.
Aug 16, 2004, 05:51 PM
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Hovertime's Avatar
Quote:
Originally Posted by Hovertime
Few more numbers-
CBP 650 8 cell nimh 2/3 AA pack - when 200 mAh were used - Voltage -6.6, Amps 15.
There is similar setup and he gets similar amp draw : https://www.rcgroups.com/forums/show...01&postcount=8
Aug 16, 2004, 07:16 PM
know it all
thats the 300h motor..the right one.

Herm

Quote:
Originally Posted by Hovertime
My motors have these markings engraved:
RK-370SD-4045
TN094329
There may be other letters covered under motor mount.


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