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Author Topic: Help with E Flite Power 25  (Read 774 times)

Offline Robert Redmon

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Help with E Flite Power 25
« on: September 03, 2011, 05:23:09 PM »
I have a new (5 flights now) E Flite Power 25 front mounted in a retrofitted Legacy that I built back in 2001 and was originally powered by a Saito. I am using the new (thick hub) APC 12/6E prop, a CC Phoenix ICE 50 Lite, Hubin 2A w/rpm set, and a 3600 mah battery. Anyway, originally 9500 rpm would not fly the airplane well enough to do any maneuvers (over 7 second laps on 65' eyelet to eyelet lines). I have been tweaking the pitch of the prop between flights, but the last flight was still over 6 seconds. Energy used on the last (best) flight was still only 1508 mah - 5 min 30 seconds flight duration. Is it possible the ESC isn't detecting rpm properly and I am not turning the set rpm? (I admit I have not checked this with my tach.)

Anyway, when I removed the prop to repitch it for the third time, I noticed the motor had some end play (not side slop or runout). Is this normal? If not, what happened in those 5 flights? Bearings go already?

Bob Redmon
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Offline Tim Wescott

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Re: Help with E Flite Power 25
« Reply #1 on: September 03, 2011, 05:31:17 PM »
How many cells?  What Kv?  If it's three cells on a 870 RPM/V motor, then 9500 RPM is pretty close to flat out.  If you've got the 1250 RPM/V motor, or four cells, then something odd is happening.

I have an eFlight Power 15 on an RC trainer; it has no perceptible end play.  But shaft replacement (and loosening) is a user-accessible item, by loosening set screws.  Perhaps you have a screw loose?
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Offline Robert Redmon

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Re: Help with E Flite Power 25
« Reply #2 on: September 03, 2011, 05:42:01 PM »
Thanks, Tim.

The motor is 870 kv and the battery is 4 cell (14.8v). I just tached it, and it is only turning 8200 rpm, explaining the performance issue. I checked the pole count input into the esc this morning, and it is correct (12), so don't have a clue where the discrepancy is coming from.

The motor has about 1/64" end play, but I just realized that I can adjust that. I had to remove the collar that sets the end play to reverse the shaft, and I guess I didn't it flush.
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Offline Tim Wescott

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Re: Help with E Flite Power 25
« Reply #3 on: September 03, 2011, 05:54:42 PM »
Well 14.8V and a Kv of 870 should give you over 12,800 RPM with no load -- and it shouldn't go down by all that much with a prop.

So something is odd.  Does the speed controller think it's going the right speed?  Are you setting the RPM at the timer or the speed control?  Are you sure of the pole count?  (a 12-pole motor should have eight magnets, unless they're getting fancy over eFlight way).
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Offline William DeMauro

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Re: Help with E Flite Power 25
« Reply #4 on: September 03, 2011, 07:47:50 PM »
Robert,
The Power 25 is a 14 pole motor. I have not flown the 12x6 thick hub so I cant really give you a starting point. But I can tell you this. First get the pole count right in your settings,especially if running "Set RPM"!!!!! Second take a short flight and get your lap time. Then move rpm faster or slower in 500 rpm increments for about every half second you are away from your desired lap time. I bet within 2 or 3 flights you will be right where you want to be. I can tell you from experience that you will probably use 2200-2600 mah out of your battery in a 5:30 flight when you get it right. Don't worry about the numbers in the castle link program for rpm, they are not always accurate(but usually are close). Go by your lap times. Good luck.
William
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Offline Tim Wescott

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Re: Help with E Flite Power 25
« Reply #5 on: September 03, 2011, 08:19:22 PM »
Quote from: William DeMauro on September 03, 2011, 07:47:50 PM
The Power 25 is a 14 pole motor.
How in heck are the model airplane people defining poles?  In normal industrial usage you count the 'bumps' on the armature, and the number pretty much has to be a multiple of the number of phases.  That would make a 14 pole motor impossible for a 3-phase motor.

Or do we count the poles in the permanent field, which means that any even number 'works'?
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Robert Redmon

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Re: Help with E Flite Power 25
« Reply #6 on: September 03, 2011, 08:31:29 PM »
William,

Gosh! I thought I had done my research...and had the pole count right. That certainly makes perfect sense. The ratio between programmed and actual rpm is about right. I am feeling really dumb right now. I will reprogram and test it  out tomorrow. Thanks!

Bob
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Offline William DeMauro

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Re: Help with E Flite Power 25
« Reply #7 on: September 03, 2011, 08:36:52 PM »
Tim,
I'm just repeating what is on the Horizon hobby website. Here is a direct paste from their website.
Lots of the motors we use are listed at 14 poles(Scorpion,AXI,Turnigy,Cobra) I do believe we count the poles in the pemanent field.

Power 25 BL Outrunner Motor, 870Kv

Key Features
Equivalent to a 25-size glow engine for sport and scale airplanes weighing 3–5.5 lb (1.4–2.5 kg)
Ideal for 15-size 3D airplanes up to 3.5 pounds (1.6 kilograms)
Ideal for models requiring up to 600 watts of power
High-torque, direct-drive alternative to inrunner brushless motors
Includes mount, prop adapter and mounting hardware
External radial rotor design—6mm shaft can easily be reversed for alternative motor installations
Slotted 14-pole outrunner design
High-quality construction with ball bearings and hardened steel shaft
Quite, lightweight operation
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Offline Tim Wescott

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Re: Help with E Flite Power 25
« Reply #8 on: September 03, 2011, 09:51:54 PM »
And here I thought I was so smart.

Eh.  An ex is a has-been, and a spurt is a drip under pressure.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Crist Rigotti

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Re: Help with E Flite Power 25
« Reply #9 on: September 04, 2011, 04:32:08 AM »
Poles are the number of magnets in the motor, not bumps.
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Offline Robert Redmon

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Re: Help with E Flite Power 25
« Reply #10 on: September 04, 2011, 08:34:44 AM »
Okay. Problem solved. 9200 rpm on the esc = 9200 measured rpm. Documentation that came with the motor did not list the number of poles. Using the motor calculator on the Castle website, 12 poles comes up automatically when the e-flite power 25 is selected, so that is what I used. Apparently, the auto fill data used in the calculator is incorrect.

Thanks, guys! 
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