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Old Oct 08, 2001, 07:10 PM
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SteveB's Avatar
Ogden, Utah, United States
Joined Dec 2000
190 Posts
Low AMPs with MEC Turbo 10 +

I'm getting a really low amp reading from my motor. I'm running a MEC Turbo 10+, 6:1 drive, Castle Creations Griffon 55 (BEC not used), Zinger 13 x 7 prop and 10 cell battery pack. The battery is around 16 volts at peak charge. I bought a Astro watt meter (tired of using someone elses) and tested the setup. I got 4800 - 4900 RPM max / 22.9 AMPS. MEC lists this motor, gearbox, simular prop combo as 7600 RPM/40 amps. I haven't pulled the motor apart to check it yet, with only four flights didn't figure it would need maintenance yet. Any ideas on what to look for? I'm guessing brushes, but not sure. This setup is in a 4 lb 2 oz AmpMaster. Performance at this point is lacking. Thanks.
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Old Oct 08, 2001, 08:33 PM
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San Antonio, TX
Joined Mar 2000
185 Posts
Did you check the timing?

I have same setup, it usually draws much lower amperage than is predicted by Motocalc (dont remember specifics) but always seems to fly just fine.
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Old Oct 08, 2001, 09:00 PM
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Ogden, Utah, United States
Joined Dec 2000
190 Posts
Patrat.....I haven't really checked the timing. I get a little sparking as the throttle is advanced, but almost none at full power. The specs I was quoting are from MEC. They say over 7000 rpm and 40 amps with about 62 oz thrust. I could really use the thrust as the airplane weighs 66 oz. I'll have to pull the motor and build a stand to check and set the timing as I can't get to it in the plane. Thanks..
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Old Oct 08, 2001, 09:10 PM
Rod
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Canada, BC, Kelowna
Joined Nov 1999
920 Posts
SteveB, I would check the following:
1) Check out the motor timing with the Watt meter. Rotate the rear bell in same direction as rotation till you get the minimum amp draw -- use a 6 cell pack to do this. Then rotate the end bell in a direction opposite to direction of motor rotation till you get a reading of (min. amp as you have read + 105 of amps you expect to run motor at (eg. 40 amps x 10% =4amps) ). Or you can rotate the end bell to the 3 position on the main body of motor. Remember to rotate in a direction opposite to rotation.
2) Check out the battery pack -- Is it large enough to maintain voltage when motor is running with the 13 x 7?
30 Have a look at the commutator, I had one that was pitted and I could not get the motor to run righe. I took it to a car shop and had them turn the comm. It worked fine fter that.

My MEC Turbo 10 draw 40 amps with a 12 x 8. I use 10-2000 Nicads, 10- 2400 Nicads, and most of the time 10-3000 NiMH cells. The T+ draws 31.5 amps with a 11 x 7. I use a 6:1 MEC gear box.
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Old Oct 09, 2001, 12:21 AM
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GregG's Avatar
Antioch,CA,USA
Joined Dec 1999
12,296 Posts
Steve, not knowing the condition or vintage of any of the other parts, I'd suspect the battery pack won't put out at the load you have. Try running this setup with the wattmeter in the circuit and see what the voltage under load works out to. I'd also check to make sure your TX throttle is advancing the speed control fully. Try these and tell us what you come up with.+
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Old Oct 09, 2001, 08:02 PM
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Ogden, Utah, United States
Joined Dec 2000
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Ok! I pulled the motor and gave it a quick check. I found a lot of carbon dust in the can, so cleaned it out. The brushes and com still look good. I checked the timing (still not positive on how to set it) it is set at 0 which is the lowest amp draw. It pulled 2.7 amp with no load, using a 6 cell pack for power. I reinstalled it in the gearbox, put on a prop and tested it again. The motor, gearbox and batteries were all purchased about 6 months ago. They have a total of 5 flights + 4 short (under 20 sec) ground runs. Voltage and AMPS were checked with a Astro Flight Whatt meter. I do have a spare gear that will change the ratio to 5:1, might try that next. Here’s what I got. Thanks for the help.

SteveB

MEC Turbo 10+ , 6:1 gearbox, 10 cell RC1700 battery pack (power tube)
Local data: 4500 FT ASL, Temp 68 F

First run 13 X 7 Zinger:
Battery voltage straight off the charger – 14.1 vdc
During run – 10.8 vdc
RPM – 5400
30 amps

Second run 12 X 8 Zinger
Battery voltage straight off the charger – 14.3 vdc
During run – 11.3 vdc
RPM – 5600
22 amps

Third run 12 X 8 APC Electric
Battery voltage straight off the charger – 14.1 vdc
During run – 11.6 vdc
RPM – 5700
18.3 amps
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Old Oct 09, 2001, 08:23 PM
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William A's Avatar
Tacoma,WA USA
Joined Jun 2001
3,828 Posts
Quote:
Originally posted by Rod
Then rotate the end bell in a direction opposite to direction of motor rotation till you get a reading of (min. amp as you have read + 105 of amps you expect to run motor at (eg. 40 amps x 10% =4amps) ). Or you can rotate the end bell to the 3 position on the main body of motor. Remember to rotate in a direction opposite to rotation.
Steve,
Did you do this last step ?.
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Old Oct 09, 2001, 08:50 PM
Rod
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Canada, BC, Kelowna
Joined Nov 1999
920 Posts
Steve, If you have advanced the timing by rotating the end bell, then your readings (amps) are still low). Are you sure it is a Turbo Ten +, your readings are closer to what you would expect from a MEC Turbo GT.
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Old Oct 09, 2001, 09:36 PM
Registered User
Crete, NE. USA
Joined Jul 2001
259 Posts
Turbo Ten

Have you cleaned the com., about every 4-5 flights you have to clean the com. with a green scouring pad, the com gets a glaze on it . I have the same problem after 4-5 flights!
Good luck! Don
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Old Oct 09, 2001, 10:55 PM
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Ogden, Utah, United States
Joined Dec 2000
190 Posts
Well I went back and set the timing to 3 degrees (per Rod's recommendation). That gave me a no load current of 5.6 AMPS, a little shy of the suggested 6.7 (2.7 + 4). With the APC 12 X 8 it ran at 11.3 vdc and 26 AMPS. Will have to wait til tomorrow to check RPM's, but suspect it will be higher than before. I'll clean the comm and put the 13 X 7 back on after work and see check that. Thanks.
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Old Oct 09, 2001, 11:19 PM
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William A's Avatar
Tacoma,WA USA
Joined Jun 2001
3,828 Posts
Maybe I'm misunderstanding, but don't you want to adjust the endbell to get your desired 'final' 40-44 amp reading while running with the prop and battery that you plan to fly with ?.
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Old Oct 10, 2001, 09:31 AM
Speed Demon
GregG's Avatar
Antioch,CA,USA
Joined Dec 1999
12,296 Posts
Well, your battery seems fine as it still puts out more that 10 V at the 30 amp level. It may also need a bit more timing advance, but this little bit wouldn't acount for the much lower than expected amp draw. Do you have a computer radio? Your ATV on the throttle channel may be set back. I hate to put things under this kind of a load but have you tried hooking the battery directly to the motor? In other words, no speed control in between the two. I've seen a speed control go bad and dropped 1500 RPM at full throttle.
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Old Oct 10, 2001, 10:07 PM
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Ogden, Utah, United States
Joined Dec 2000
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Well checked the RPM and AMPs after resetting the timing, still only getting 5400 RPM & 30 AMPS. I got to thinking about the gearbox, so pulled it apart. It had a slight drag, so I polished the shaft and re-oiled the bearings. That got me to 5700 RPM, still short of 7000 though. Someone asked about my radio, it's a basic Futaba Conquest 6 channel. Even ran the trim through and only got a slight change in RPM. I also tried connecting the battery directly to the motor and still stayed between 5700 - 5800 RPM. I'm about ready to look at a new motor....
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Old Oct 10, 2001, 11:28 PM
Rod
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Canada, BC, Kelowna
Joined Nov 1999
920 Posts
Steve,
One thought, did you remember that the motor is turning counter-clockwise when viewed from the rear? So you rotate the end bell clockwise when viewed from the rear.

As a last resort why not have your commutator turned at a car hobby shop. I did this to the MEC T+ that I could not get to perform and performance was restored. It cost me $5.00 and was worth the expense. If you created a lot of brush dust after one flight this could cause some damage to the comm. Mine looked OK, but on turning it was a different motor.
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Old Oct 12, 2001, 10:25 PM
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Ogden, Utah, United States
Joined Dec 2000
190 Posts
Want to thank everyone for their help. I searched around and finally found a hobby shop that had a comm lathe. They turned the comm for me, and recommended I replace the brushes soon (they are on order). I got in a quick test run before dark, 7100 RPM @ 38 AMPS. That's a big improvement from before. I'm hoping that the weather will be nice in the morning, so I can get in a few flights.
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