C-47 Building tips. - Page 4 - RC Groups
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Aug 16, 2004, 07:39 PM
Always right
Hovertime's Avatar
Quote:
Originally Posted by hermperez
thats the 300h motor..the right one.

Herm
Thanks, Herm,
At this point I will leave this issue of strange difference in amp draw as it is, with possible explanation as lipo vs nimh cell differences.
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Aug 16, 2004, 08:10 PM
Registered User
jfail's Avatar
Is everyone who has flown successfully using the COG as per the C-47 manual or are people finding a better COG?
Aug 16, 2004, 08:48 PM
MINE!
Mick Molloy's Avatar
My first flight was as per the instructions at 55mm and it was a flight but a bit of a handfull i will be moving it aft 10mm and trying again.
Aug 16, 2004, 09:12 PM
Registered User
I just checked mine again....about 62mm......and I' got up trim in it for level flight.

I first tried it at 75 mm and it was too tail heavy. I have never flown it at 55mm.

I have also painted my plane and put a little weight in the nose with a TP 2100 3s1p.

Hovertime saw it fly....at least this plane has a wide range of CG without disaster.

Wish I could say the same for the P-51...sigh.
Aug 17, 2004, 02:19 AM
Zoom, zoom...
Trikster's Avatar
I have 90 minutes total flight time on my DC-3. I have the following for equipment:

3x Naro servos
GWS 6-channel Rx
CC Pixie-20p
Gen 2 TP 2100 2s1p

I am balanced around the 75mm from LE of center wing section. Still a touch tail heavy, but flies very nice (even in lots of wind as I found out tonight). I am thinking about putting about 1/4 oz in the nose to see if anything improves. I doubt it, but what the heck. My ESC surges just like yours is apparently. As the motors get older, I notice the surging a bit more every flight. I usually fly at 1/2 throttle and have only recently started to hear the hum hum hum of the motors. On the maiden, I only heard this at full throttle. I seated the motor brushes at 1.5v for 4 hours. One motor still arced a bit, but the other didn't. Not sure what is going on with the ESC here.

As for building tips... I really didn't do much that hasn't been posted by other folks. I took extra pieces of the pushrod tubing to use as anchor points for the rudder, elevator and aileron wire joints. I glued the tubing into each control surface but let the wire move freely inside the tubes. There is a tiny bit of swiveling in the ailerons and didn't want any binding if I could help it. All my epoxy joints used a 50/50 mix of micro balloons. I use 12 minute epoxy and coupled with the MB, it settles into cracks and levels off very nicely. Everyplace else, I use GWS glue. As someone mentioned earlier, you brush it on nice and even (and sparingly). Then you stick the two pieces together and pull apart. I usually only let the halves stand for 5-7 minutes as I put very thin coats on the foam before I stick them back together. I then use #64 rubber bands to hold things in place as everything cures. My elevator pushrod has an additional angle bent into it to stick it 1/2 inch further out of the fuse to accomodate the control arm of the elevator. I used the inner hole on the rudder and elevator. I use Dubro EZ-Links on the servo end of things. I CA'ed balsa mounting blocks for the servos. I prefer to screw mount my servos.

I cannot think of anything else I did differently than the manual. I did have to do a lot of sanding on some parts to get a clean joint. The dihedral of the main wing was a really poor fit out of the box on my model. 2 hours later and both tips are within less than +/- .5 degrees.

I wish there was another choice of ESC with a 6v cutoff that I could try. I cannot imagine that I am tripping the cutoff early. I have tried 6v, 5.2v (whatever the default is) and no cutoff and still get the surging. It is kind of annoying.
Aug 17, 2004, 03:17 AM
Always right
Hovertime's Avatar
Quote:
Originally Posted by Trikster
My ESC surges just like yours is apparently. As the motors get older, I notice the surging a bit more every flight. I usually fly at 1/2 throttle and have only recently started to hear the hum hum hum of the motors. On the maiden, I only heard this at full throttle.
.............
I wish there was another choice of ESC with a 6v cutoff that I could try. I cannot imagine that I am tripping the cutoff early. I have tried 6v, 5.2v (whatever the default is) and no cutoff and still get the surging. It is kind of annoying.
Man thanks! I though I was going crazy and imagining it
I know for sure in my case its not LVC, since when I do reach LVC it is very different from what I experience.
But in your case it may be LVC as you lipos are getting older.... Do you fly until LVC? LVC sounds hum hum hum; and in my case it sounds as if glow engine misfires once in a while, I should record the noise of my problem and soft LVC, and post it somewhere
Aug 17, 2004, 03:22 AM
Always right
Hovertime's Avatar
Oh and there are many others, more advanced brushed esc's like ones made by Jeti, and I also have high hopes for upcoming GWS lipo esc line! Hopefully they won't be late
Aug 17, 2004, 03:42 AM
Zoom, zoom...
Trikster's Avatar
The packs I have are exclusive to the DC-3. I have two of the Thunder Power 2100 Gen. II 2s1p packs. 90 minutes is between the two packs. I charge them on my AF 109 charger so they are well maintained. So far, it does not seem to matter if I fly to LVC or not. I get the surge all the time. I don't know if "things" work this way or not, but I am wondering if the switching frequency isn't high enough in the CC unit to handle two motors. Perhaps with two motors, the motors think they are being switched at half of what the ESC is rated at?? I don't know the finer points of electrical stuff, so I am just guessing. If the amp draw wasn't as high per motor, I had thought of running two Pixie-7p's off of one 2100...
Aug 17, 2004, 03:44 AM
Insert Witty Comment
Suntzu's Avatar
So whats the latest on 2S vs 3S on the 300H in the C47?>


Need 3S or is 2S enough? Or is 3S killing the motors?
Aug 17, 2004, 06:13 AM
Always right
Hovertime's Avatar
Quote:
Originally Posted by Trikster
The packs I have are exclusive to the DC-3. I have two of the Thunder Power 2100 Gen. II 2s1p packs. 90 minutes is between the two packs. I charge them on my AF 109 charger so they are well maintained. So far, it does not seem to matter if I fly to LVC or not. I get the surge all the time. ...
Do you see different pulsing when you hit LVC compared to "regular pulsing" ?

As far as 2 motors vs 1 - it does not matter, there could be 4 or 10 motors, or a light bulb as far as ESC is concerned, as long as amp draw is within limits.
Aug 17, 2004, 07:39 AM
know it all
Surging could be caused by radio interference.. the radio glitches, the esc shuts down the motors, the radio comes back on..the motors come back on.. repeat, all you see is the motor surging.

If its bad enough, the motors will not even reach full throttle.. add a third capacitor across the motor terminals, twist the wires going to the motor..

If by surging you mean the hum-hum made by twin props then that is normal and part of the twin fun.

Herm
Last edited by hermperez; Aug 17, 2004 at 07:42 AM.
Aug 17, 2004, 08:03 AM
Always right
Hovertime's Avatar
Thats all good suggestions, Herm, but i'm pretty sure its esc itself.
Reasons-My c-47 has berg 5 receiver, so first thing that i thought that motors surge because of bergs "microprocessor at work" as instructions say : "you may notice slight servo movement, with no input from TX, thats normal" or something along those lines.
My servos however did not move a bit. I have also tried simple 4P receivers (both shifts, 3 different radios , etc etc.
My motors surge most noticeably at very low rpm, then going faster and faster its difficult to notice. At WOT there is no surging, also motor sound changes as esc goes from switching power on /off to fully on.
When I reach LVC and Pixie starts soft power ramp down it pulses. During LVC pulsing RPM varies a lot. If I reduce throttle and pack is able to sustain voltage above LVC pulsing stops. This LVC pulsing and motor rpm fluctuation that i experience are two completely different things.
Two Pixie20P that I owned acted the same, also the third one that I just got from CC as replacement/comparison unit.
I also should add that brushless setups has steady rpm with those receivers, and radios.
Also I have no other brushed esc's to compare.
C-47 Motors run steady when powered directly from batteries.
This surging is probably hard to notice when flying, but pretty obvious on the bench, slowly advancing throttle.
Anyways, this is a bit off topic So I'll stop now, just add that this surging is a bit annoying....
Aug 18, 2004, 08:27 PM
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Hovertime's Avatar
never mind
Last edited by Hovertime; Aug 18, 2004 at 08:32 PM.
Aug 18, 2004, 09:45 PM
Registered User
I am using TP 2100 3s1p blue stripe. No surging here....only harmonic warbling when the motors are pushed too hard.....2/3 thrott or more.

I burned out Sprite 25 , now I am on a Jeti 3o heli , and it seems fine , for now.

I keep losing props. I will be trying the Graupner 2mm adapters and their 4.75 x 2 props. I can't get a 5x3 for the Graupners, at least that I can find.

There is a fine line with the 3s1p , the motors may not like a bigger prop with that much voltage. I just want a reliable flyer , no need for vertical climb out here , but it is nice to have the option of power when you get in trouble.

Then again, how much and where can you get pairs of these motors??

It may be the smart thing to treat the motors as expendable, and push the heck out of them. Hmmm....
Aug 18, 2004, 11:41 PM
Zoom, zoom...
Trikster's Avatar
Its definately the ESC causing the surgeing. I have tried different Rx's, different radios (+/- shift as well)... I am wondering more and more if the switching frequency really isn't high enough for two larger motors.

Put flights 10 - 13 on 'er tonight. Have been trying different mixing and still think all that is needed is about 20% A/R mix.


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