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Old Jun 19, 2002, 04:53 PM
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maintaining an Atomic Force motor

When is it time to turn the comm? Also, when it is time can I use a micro metal lathe to do this instead of a comm lathe? If so, what are the key issues I need to be aware of to do this? Thanks, Joe
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Old Jun 19, 2002, 05:18 PM
bps
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JoeR,
I got about 15 flights or so out of my AF motor. What mine did was it began to cause severe glitching about 1/2 way through a battery charge. Just when the motor, batteries and speed controller heated up I would get the glitching. I flew it at night once and noticed the brushes would spark and then the glitch would happen. I am going to go brushless.
JEB
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Old Jun 19, 2002, 08:14 PM
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the arc'ing (sparking) is pretty bad unless you advance the timing properly. If timing is set correctly, it's still there, but minimal. If not timed correctly for the current you're drawing, expect very low brush life and lots of heat. If timed correctly, on 10 cells,.. expect 30~40 flights, maybe more depending on throttle usage,.. per set of brushes. I like to true the comms (micro lathe) after a few brush changes.
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Old Jun 19, 2002, 10:43 PM
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Thanks,
GWright, I am using this in a LMH Corona helicopter with seven cells. I got about 8 - 5 minute flights before I started getting glitches. Can you enlighten me on how to time this correctly? Can I time it without a watt meter? I have a micro-watt meter but that is only go to 15 amps. Thanks, Joe
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Old Jun 19, 2002, 10:58 PM
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15 amps will do it since you'll be timing no-load. You need to advance the timing 10% of what your average current is. Connect a 5V source to it(or a 5 or 6 cell pack will work, never used 7,..rpms might get a bit high). With the motor out of the heli, of course (no load on it), twist the endbell a tiny bit back and forth untill you find the lowest current. Do this quickly, only 20~30 seconds or so running. Now,.. compute what you're average current is. Say you're running 3000mah nickle metal hydrides,.. a 6 minute flight would equate to just under 30 amps. you're probably running 1700's though,.. which means with your 7 to 8 minute flights, average current is about 15~16 amps. 10% of that is 1.6 amps. Whatever the no-load neutral timing is (guessing 2.3 amps for the atomic force), then advance the timing (turn the endbell in the direction you hear the rpms INCREASE) untill you're at 3.9 amps (2.3 no-load neutral, plus 10% of the average draw in flight). It's better to be a little over-advanced than under-advanced,..but by a "little", I mean a tenth or two on the current. arc'ing should be less now. You do have the three capacitors installed I hope? and also a schottky diode will help the speed controll run a bit cooler since it's run at part throttle most of the time in a heli.
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Old Jun 19, 2002, 11:10 PM
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Thanks Gary, I will read and digest. I am using 3000 mah NiMHs, the cheaper ones (HR-SC?). I am only able to put 2000mah back in them after a flight though. Past 5-6 minutes I am only able to hover a few inches off the ground. I have the caps and a diode installed as directed by LMH and CC. I thought I remember someone mentioning 19 amps draw while hovering. I am probably wrong on that.
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Last edited by JoeR; Jun 19, 2002 at 11:13 PM.
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