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Old Dec 14, 2010, 08:23 AM
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Less than expected power from my setup - any ideas?

I am running an Ammo 24 33 3180 kv inrunner with a 4.75x4.75 prop on a Castle Creations Pheonix 25 amp esc. I should be seeing 25+ amps on 3s but I am only seeing 11 amps. I have the esc set to soft cutoff and the voltage set below 10v. Low-normal timing - tried both. Pack voltage was 12v under load.(I used an oversized pack just to make sure it was holding voltage under load)

Any suggestions?
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Old Dec 14, 2010, 08:33 AM
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Is your Tx set for full throttle range?
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Old Dec 14, 2010, 08:44 AM
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I have gone through the fixed end point procedure twice. I believe it is.
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Old Dec 14, 2010, 09:02 AM
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Have you got a smaller prop to try, just to see if the 4.75x4.75 is over-loading it.
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Old Dec 14, 2010, 10:03 AM
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Only another 4" prop with less pitch. It is a known setup recommended by the model designer. He runs it at or near 300 watts and 28 amps. Static. he says in flight it unloads to approx 20 amps. I am measuring 135 watts and 11.5 amps static.

I have another esc to try it on but I need to remove the existing bullets as they are a different size than this motor's connectors.
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Old Dec 14, 2010, 10:16 AM
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I have similar situation where a motor is said to deliver 165W ... but no matter what prop / combo I try - I don't get more than 115W ... if I run on the recc'd set-up - I get ~110W

But the model flies well on it - so I accept it and benefit from longer run times !
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Old Dec 14, 2010, 10:50 AM
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I cannot run at less than half power. Plus it's a little pylon racer. Long run times are not the goal. Speed is.
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Old Dec 14, 2010, 10:51 AM
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Certainly your performance doesn't match the MotoCalc computation:

Motor: Great Planes Ammo 24-33-3180 (#5155); 3180rpm/V; 1A no-load; 0.0799 Ohms.
Battery: Thunder Power TP2650 (G4 ProPower 45C) (45C); 3 cells; 2650mAh @ 3.7V; 0.003 Ohms/cell.
Speed Control: Castle Creations Phoenix 45; 0.0026 Ohms; High rate.
Drive System: Direct; 4.8x4.8 (Pconst=1.47; Tconst=1) direct drive.
Airframe: Anything you want.
Motor Amps = 27.3
Motor Volts = 10.8
Input (W) = 294.8
Prop RPM = 23945
Thrust (oz) = 19.7
PSpd (mph) = 108.8


Have you checked the Kv of the motor?
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Old Dec 14, 2010, 10:54 AM
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Exactly. I am getting 135 watts at 12v.


It has to be something with my esc. I will have to cut off the small bullets and run it on another controller. If it still has low power I will have to assume there is something wrong with the motor.
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Old Dec 14, 2010, 11:30 AM
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Quote:
Originally Posted by mexico View Post
I am running an Ammo 24 33 3180 kv inrunner with a 4.75x4.75 prop on a Castle Creations Pheonix 25 amp esc. I should be seeing 25+ amps on 3s but I am only seeing 11 amps. I have the esc set to soft cutoff and the voltage set below 10v. Low-normal timing - tried both. Pack voltage was 12v under load.(I used an oversized pack just to make sure it was holding voltage under load)

Any suggestions?
What rpm are you getting?

It wouldn't hurt to make a no-load rpm measurement either, that would verify that you are getting 100% throttle out of the Phoenix.

Amps and volts without rpm is only part of the picture.
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Old Dec 14, 2010, 12:12 PM
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I do not have a tach but I cannot be getting 100% of the expected rpm at only 40% of the expected power.
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Old Dec 14, 2010, 04:56 PM
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Quote:
Originally Posted by mexico View Post
I do not have a tach but I cannot be getting 100% of the expected rpm at only 40% of the expected power.
Well that's the issue.

If you could measure the no-load rpm, then you could compare that value with a simple kV*battery voltage. That would tell you if you are even getting full throttle from your ESC.

Tachs are just another analysis tool, like a wattmeter.

Do you know anyone with a tach--like an old nitro flyer?
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Old Dec 14, 2010, 06:56 PM
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And if I am getting full RPM? How could that be possible? Full RPM at half power?
I don't know anyone that has a tach. Would an old nitro flier even have a tack that could measure no load rpm on a small brushless motor?

I ran the motor on a 2nd esc and got the same numbers. I even tried it on other model memories on my TX. Models that I know run fine at 2200 watts and 1800 watts and 500 watts. I know the Tx works fine.

At this point I can only assume it is the motor.
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Old Dec 14, 2010, 07:50 PM
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http://www3.towerhobbies.com/cgi-bin...&I=LXPT31&P=ML

Ask Santa, nicely, for one!

"RC without a tach" is like "life without beer!"
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Old Dec 14, 2010, 08:11 PM
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I can honestly say in ten years of e flying I have never seen anyone use a tach.
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