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Old Feb 14, 2004, 03:17 PM
Registered User
Victoria BC
Joined Feb 2004
46 Posts
Graupner Mini Piper=short air time,need help

Having a problem keeping the piper in the air or ground tests for more than a 5 or 6 minutes.
I rebuilt the plane and am using the following gear.
Graupner SPEED 300 motor,Gunther 5 x 4 prop,GWS ICS - 300E speed control,GWS Naro 4-Channel receiver,Blue Bird BMS-371 servos.
For batteries I started off with 8.4v, 700mha hecell NiMH AAA's then went to E-Tec 7.5C LiPo 1200 mAh 2S1P 7.4V.
I was getting about 4.5 mins. with the NiMH, and about 6mins with the LiPo's 3/4 throttle.
Something seems very strange. I realize direct drive motors consume more energy but this seems a little off.
I tried setting up a GWS EDP-300 direct drive motor externally but got the same results.
The batteries run my son's GWS Beaver (15 mins. on the NiMH's) with good air time so it's not the batteries.
If any one sees something in this setup that doesn't look right I'd sure appreciate a bit of advice.
Cheers Guys
B.Fawlty
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Old Feb 14, 2004, 03:58 PM
Registered User
Mississippi
Joined Dec 2003
109 Posts
Mine flies 20 minutes on the Graupner 7.2v 1000mAh NiMh that I got from hobby-lobby....also it flies longer and better after a few flights when the motor breaks in....
It should fly that long on the lipo, though.......do you use a charger that you can see how many mah it uses or replaces when on charge? Maybe you aren't getting a full charge.
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Old Feb 14, 2004, 04:01 PM
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Mississippi
Joined Dec 2003
109 Posts
Oh, also I use a 4.9 x 4.3 prop.......that would make it last a little longer probably....climbs a little slow, but flies good once up to speed....
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Old Feb 14, 2004, 04:40 PM
Registered User
Victoria BC
Joined Feb 2004
46 Posts
I think my batteries are OK I usually check them out with a volt meter under load(auto headlight).
The only difference I see may be the prop, but I've noticed a lot of guys use this gunther prop.Is that a GWS prop your using?
The batteries and speed control get pretty hot because of the fast discharge
Cheers
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Old Feb 14, 2004, 04:55 PM
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N.J.
Joined Dec 2002
218 Posts
Something is definitely wrong. You said you rebuilt it - what does that mean? Is is substantially heavier from epoxy? I have a mini piper that I fly on the 2s1p 1200etec & I can keep that thing in the air for at least 1/2 hour easily with power to land - and the battery is just warm when I check it after landing. I would guess that with the graupner 5 x 4 prop direct I'm pulling about 2.5 amps or so at 1/2-3/4 throttle (don't know for sure). Did you align the cooling hole in the motor up with the intake vent at the front of the plane? Although I don't think that would knock your flight times down so dramatically, I just dunno.
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Old Feb 14, 2004, 05:20 PM
Registered User
Victoria BC
Joined Feb 2004
46 Posts
I got the plane from a friend, the front end was totalled so I rebuilt it. I don't believe it's the motor because I did try it with a different direct drive motor I bought as a replacement same specs as the one in use and got the same result. Those timed tests were made stationary (on the ground) so flghtweight had no bearing. I noticed you use a graupner 5X4prop I wonder if theres any difference between that and the gunther unit, i doubt it. I've been flying the plane for about a month now but 5 mins. per battery doesn't quite cut it not to mention I had to repace my burnt out JST connecter coming off the speed control.
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Old Feb 14, 2004, 08:05 PM
WOOOOsssSSSShhHH !!
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Long Island , NY
Joined May 2003
1,007 Posts
ello !

Ive got an ol' mini pipe with a BL in it now from stock form.

First of all..you mentioned you used a gunther prop , be sure the letters are facing you when on prop shaft.

check your charger's output. Make sure you batts are putting out max output.

The sp300 enough to fly this bird. Especially with the lipo's you got .

My MiniPipe now has a MiniAC 1216 with the good ol' gunther props still. i use a bunch of old 7 cell 700nimhs (tipsy batt) and get about 8 mins flight time. ROG in 10 ft. Will throw some lipos in her someday but the added weight of the nimhs makes feel a little more solid. I ve reblt the nose several times : )
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Old Feb 15, 2004, 11:42 AM
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TN
Joined May 2000
1,136 Posts
Fawlty

The only thing that I can think of that would cause the problems that you are having is the motor. If you have a Speed 300 6V motor, that would be a problem. The Mini Piper is designed for direct drive with the Speed 300 7.2V motor.

The 7.2V motor is very different than the 6V motor. The Kv is much lower, you should be flying for at least 15 minutes.

Mike Hines
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Old Feb 15, 2004, 05:29 PM
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Victoria BC
Joined Feb 2004
46 Posts
Thanks for the info guys
Sparrow: to clarify one thing do you have the lettering facing towards the plane or is it the opposite.
Mike: Ya I'm pretty sure I have the 7.4v unit, I did do that extra test with the external 7.4v motor with no change in running time.
I did a test to check the amps being drawn and it's way to high, up around 8amps, no wonder the jst plug fried.
I also did a resistance check doesn't seem to be any shorts in the system.
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Old Feb 15, 2004, 09:26 PM
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Long Island , NY
Joined May 2003
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facing the plane...

as if you can see lettering on the prop if you were looking from cockpit area forward.

Good thought there M Hines regarding the speed300 plus 7.4v.
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Old Feb 15, 2004, 09:39 PM
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Victoria BC
Joined Feb 2004
46 Posts
Thanks Sparrow, ya thats the way I had the prop set up.
After rereading my reply I noticed I said the voltage was 7.4v for the motor, I meant 7.2v.
I'm going to try a different speed contol tomorrow, if thats a nogo I guess time for a new plane
Cheers;
Fawlty
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