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Old Jan 04, 2010, 08:19 PM
idiot (non-savant)
tdrnmartin's Avatar
Cuyahoga Falls, OH
Joined Jan 2005
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Question
Power system head scratcher: E-Flite PT-17 Stearman with Power 15

I received a E-Flite PT-17 Stearman as a Christmas gift this year

I've almost completed the build - it really goes together well.

I've run into a situation that I haven't experienced before and I'm wondering if anyone else has had this happen: The power system is only pulling half the expected current/power.

I'm using all the recommended power components:

E-flite Power 15 motor
E-flite Pro 40 ESC - BEC disabled at recommendation of E-flite
and an external BEC - Castle Creations BEC SWITCHING REGULATOR
E-flite 3200mAh 3S 11.1V 20C LiPo with 13AWG wire
APC 12X6E prop

The only change is that I'm using Dean connectors instead of the native EC3 connectors.

I'm also using the following other components:

Futaba 9C - original Heli version 72Mhz
Castle Creation (Berg) 7 Channel receiver
2 X HS-225MG Servos
2 X HS-85MG Servos

I've tried changing the timing in the ESC from 15 to 20 degrees and tried changing the Freq. from 8kHz to 16Khz. I've changed the throttle pulse width to the longer range (which is necessary with the Futaba 9C TX). I've tried using an old Hitec 4 Channel TX that I learned to fly on years ago. I've tried 2 different RXs ( berg 4 channel and a seeker 6). I've tried a E-flite pro 25 ESC and every time I get the same result. The motor is only pulling about 17.5 amps. Every review that I've read for the Stearman with the E-flite power 15 as the motor states that they are seeing full current in the range of 36Amps. I'm at a loss as to what is going on. The only thing I haven't tried yet is a different battery and I plan to try that next.

Tried a Hyperian 3C 2200 35C pack that I use in my Trex 450. The same results. At this point, the only items that I have not changed out as part of my trouble shooting is the prop or the Power 15 motor. I wonder if there is something wrong with the motor?


Any ideas?
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Last edited by tdrnmartin; Jan 04, 2010 at 08:40 PM. Reason: update
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Old Jan 04, 2010, 08:55 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
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Unless you haven't got the full throttle range... all I can see is a motor problem... can you try any other motor on your set-up to see if it pulls its full current?

Motocalc suggests ~38A and you are obviously not getting that.
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Old Jan 04, 2010, 09:11 PM
idiot (non-savant)
tdrnmartin's Avatar
Cuyahoga Falls, OH
Joined Jan 2005
89 Posts
I think I have the full throttle range, as I changed the menu option in the ESC to the longer range to match the Futaba. (I actually had to change this setting as if I didn't, the motor would pulse at the full throttle. I had the same issue with the E-flite Pro 25 ESC and and some BP out runners on this same Futaba 9C TX):

"Programming Menu 4 – Throttle Input Range (PWM)
The default setting is 1.2ms to 1.8ms and should work with most radio systems. This option allows for proper throttle input with many different radio systems. However, some radios have a wider output range, and may give a more linear response with the 1.1ms to 1.9ms range. If you feel there is too much “dead” area in the stick movement near full throttle, try adjusting the end points in your radio, or change to the wider input range. Be aware that if these settings are not correct, it may be impossible to arm the controller."


Yes, I think I can try another motor. I just don't know if my smaller motors have bullet connectors that will mate up to the E-flite 40 amp pro ESC.
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Last edited by tdrnmartin; Jan 04, 2010 at 09:21 PM. Reason: update
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Old Jan 05, 2010, 07:13 AM
idiot (non-savant)
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Cuyahoga Falls, OH
Joined Jan 2005
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OK, hooked up a BP 2217-9 out runner to the Stearman's ESC and it did reach it's max current, which by the way is also about 17.5 amps. I them connected the Power 15 to the ESC of the ThreeDee that the BP 2217-9 is mounted on with the same results as before. It only pulled about 17.5 amps. I also tried the Hyperion 3C lipo with both setups, just to make sure. It seems as if the issue is with the motor, but the really odd thing is that if I didn't know that the current should be around 36 or 38 amps, I wouldn't even think anything is wrong. The motor is running fine and seems to have good power. I'm just concerned that it won't have enough to fly the Stearman well.

and by the way, I don't know what I was thinking with the comment about the bullet sizes. I had already tried a 25 amp speed controller on the power 15 and that has the exact same size connectors as every other motor I'm already using......
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Old Jan 05, 2010, 08:56 AM
Marion
USA, NC, Hillsborough
Joined Oct 2003
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Could your Amp measurement be wrong ???
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Old Jan 05, 2010, 09:08 AM
idiot (non-savant)
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Cuyahoga Falls, OH
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I suppose so, but I'm using an Asto watt meter that I've had for some time now. I'm going to say no, as it seems to be working correctly for other measurements that I've taken. I beleive the readings I'm getting for the BP 2217-9 motor on my ThreeDee are the same that I've gotten before. I beleive those readings are good, based on the manufactures specs on the motor.
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Old Jan 05, 2010, 09:19 AM
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Chattanooga, Tennessee, United States
Joined May 2003
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Just for laughs, if you can measure rpm, why no see what the no-load rpm of your Power 15 is? Is it possible that your motor has extra winds and so is lower Kv than it should be?
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Old Jan 05, 2010, 09:21 AM
idiot (non-savant)
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I think so, I need to find a quick way to mark the motor so the meter will read it.
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Old Jan 05, 2010, 11:11 AM
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Chattanooga, Tennessee, United States
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Quote:
Originally Posted by tdrnmartin View Post
I think so, I need to find a quick way to mark the motor so the meter will read it.
I wrap a strip of white tape around the bell (I use file folder labels) and with a black Sharpie paint two patches diametrically opposed... shine a flashlight at it from the side...then the tach (aligned with the flashlight beam reflecting from the tape) reads it as 2-blade. Bingo!

This photo shows the patches... obviously you don't want the prop!!!!
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Old Jan 05, 2010, 11:14 AM
idiot (non-savant)
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Cuyahoga Falls, OH
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I used 2 small strips of silver tape on either side of the motor - at full throttle i was reading about 11,160.
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Old Jan 05, 2010, 11:21 AM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
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What was the voltage? If it was under 11v then the motor's Kv is well over the spec of 950Kv...that is in the wrong direction for explaining low amp draw!
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Old Jan 05, 2010, 12:43 PM
idiot (non-savant)
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Cuyahoga Falls, OH
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The battery was fully charged, so I will say around 12. I'll give it another try with the astro meter attached. It was hard to get a steady reading. I wonder if that was due to the size of tape strips I used. Would I be better off to have 3 or 4 instead of just 2?
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Old Jan 05, 2010, 01:09 PM
idiot (non-savant)
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Cuyahoga Falls, OH
Joined Jan 2005
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OK, I think part of the light colored label on the motor was messing up the reading. I used some black electrical tape to cover that up and then used the silver tape:

12,780 RPM @ 11.77V

Sounds like this is still not what you were expecting.....
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Old Jan 05, 2010, 01:28 PM
idiot (non-savant)
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Cuyahoga Falls, OH
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Just to make sure that my use of light on dark vs your dark on light method didn't mess up the results, I retested using your method:

11,550 at 11.86 volts

Still up there.....
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Old Jan 05, 2010, 05:08 PM
idiot (non-savant)
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Cuyahoga Falls, OH
Joined Jan 2005
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Now I am questioning if my astro watt meter is working properly - at least as far as the current reading. I just tried 2 additional props: APC 11X7E and APC 12X8E, beside the recommended 12X6E. All 3 props used just under 17.5 amps at WOT. That shouldn't even be possible. The voltage readings at least seemed reasonable. The 12X8E dropped the battery voltage to 10+ volts, where the others were all above 11 and the charge was still fresh for all three props - short run times to take readings. The power 15 is the largest brushless motor I own. The meter appears to work with the others because they don't need as much current. Does it even seen possible that a current meter could limit it's reading to some arbitrary maximum value?
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