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motor wont spin up

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motor wont spin up

Old 11-08-2006, 07:04 PM
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Default motor wont spin up

My friend has a Trex 450 XL CDE. When we try and spin it up it "pulses" for lack of a better term. It goes ...rrrrrrrit, rrrrrrit, rrrrrrrrit and doesnt ever get up to speed. I have seen this problem before on a walkera 36 that I had but couldnt track it down then either. It has cost both of us an ESC each. Belt tension seems ok. Motor pinion/main gear mesh seems good. Main head and rotor spin freely. The last time his burnt up an esc it ran up to speed (strapped down on top of my bar) and ran at full rpm for about 30 seconds then just shut off. Then it did the rrrrrit, rrrrrrit thing and poof! out comes the yellow smoke! He fried the battery too (1800mah 10c 11.1v) now it reads a big ZERO on the voltmeter. What would cause all this. This Trex has never been off the ground yet.
oh yeah he has a BL420 3200kv brushless, 13 tooth pinion, 35A Align brushless esc, apex ms 1300mah 15c battery (hes got a MegaPower 2100mah 15c in it hes not using yet) and spektrum dx6 TX/RX

HELP!!!!!
Old 11-09-2006, 03:02 AM
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Default RE: motor wont spin up


ORIGINAL: rawvoodoo

The last time his burnt up an esc it ran up to speed (strapped down on top of my bar) and ran at full rpm for about 30 seconds then just shut off. Then it did the rrrrrit, rrrrrrit thing and poof! out comes the yellow smoke! He fried the battery too
HELP!!!!!
You should not load the ESC like that. You're making it give full power continuosly and they're not designed to do that. Had that been free to fly outside how high do you think it would have gone at full power for 30 seconds? Out of sight...

ESCs can be pulsed at max power but no more.
Old 11-09-2006, 02:36 PM
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Default RE: motor wont spin up

Oh cmon! After seeing what these things can do in the air spinning it up while strapped down to a bar is nothing. How else do you check you blade tracking? And idle up!? Your rpm is maxxed practically all the time. Tell me again how a series of rolls and loops then some knife edge tic-tocs is somehow less abusive to the esc than just spinning up the blades to get everything running right before setting it out to the air. I have seen any number of people on these forums using a lazy susan to strap their heli to when servicing and they need to spin it up. The problem we are having starts right off the bat. The rotors wont spin up a full turn let alone with enough headspeed to hover And thats with a brand new ESC so it cant be that we ran it up while strapped down.We havent even got this one up to speed.
Old 11-10-2006, 09:12 AM
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Default RE: motor wont spin up

Measure the resistance of the motor coils, if one is much lower than the others then you fried the motor as well and it in turn could fry every new ESC you put on it. If one coil is much higher resistance (or open circuit) the motor is still fried but your new esc should be fine.


You said you ran it strapped down at full power for 30 seconds then it stopped. You burnt it out, it's that simple. Hard 3D does not put that sort of load on a motor or esc. Constant switching between positive and negative pitch gives short bursts of high power and moments of almost zero power. It's the average power that is important.
Old 11-10-2006, 02:36 PM
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Default RE: motor wont spin up

I see what you mean about the average load on the esc. But I still think that makes them a bit too fragile. I mean Ive seen an RC truck pulling a real car. Full power, tires spinning and actually pulling the car about 5-10 feet for at least a full minute. Same electronics....motors and an esc. Nothing fried. I really think it should have been able to hold up under what little strain we may have put on it. But I've told my friend not to mess with it till we get it to the Pro Guy at our Not-so-LHS. He can test all the motors and stuff. Id hate to find hes burnt up the esc, battery AND motor all before getting the bird in the air at all.
Old 11-18-2006, 05:03 PM
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Default RE: motor wont spin up

I have similar symptoms with my ESC, although I have never experienced smoke or even heat from either the ESC or the motor, and neither shows any signs of being burnt. My motor has never run under any load. For setup I disengaged the pinion from the drive gear. I made a lengthy post on another thread an hour ago, but this thread also seemed relevant. When I first plugged everything in, the motor ran, although throttle was backwards. I reversed the throttle channel in the TX and then went through the programming procedure. Now the motor just stutters a bit when I throttle up, but never actually does anything. I've tried reprogramming many times, and all chirps from the ESC confirm that I've set it as intended (1-1, 2-2, 3-3, 4-2, 5-1). Is it possible that I damaged either the motor or ESC by running it for a few seconds unloaded? I've never heard of this being a problem, and certianly never had such a problem with electric aircraft in the past. The motor does not appear to be burnt, i.e., all coils are still bright shinny copper color, and it doesn't smell burnt. Any ideas?

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