Electric motor issue-Black and Decker trimmer

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  #1  
Old 11-14-10, 01:59 PM
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Electric motor issue-Black and Decker trimmer

I have a Black and Decker TR165 electric hedge trimmer. It quit working the other day. Everything tested fine back to the motor. After taking the blade assembly free from the gear shaft, I powered the motor and it ran. However, I noted some sparking at the area of the brushes. I let off the switch and then tried to power it again and...nothing. I rotated the gear shaft a few turns and the motor ran OK. Then I noticed that if I let off the switch and powered again before the shaft/motor stopped rotating, the motor would run. Once the shaft/motor came to a stop, for the most part, it would not run again until I would manually spin the shaft/motor a few times and then the motor would power.

So, the questions are...could this be the brush and how would I tell (yes, the trimmer is cheap but brushes are only $0.89)? Why do I have to manually rotate the shaft/motor to get it to power up but a quick on/off action of the switch keeps the motor running as long as the motor is spinning?

My electrical knowledge is next to nil and this is more of a curiosity issue then anything else. Plus, the trimmer was a cheap auction find that has worked fine until now. A big thanks to everyone!!!
 
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Old 11-14-10, 02:43 PM
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At 89 I'd replace the brushes just to eliminate it as a possible problem.
 
  #3  
Old 11-14-10, 05:50 PM
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Originally Posted by thejc2C View Post
My electrical knowledge is next to nil and this is more of a curiosity issue then anything else.
Oh, I dunno ... You knew enough about the subject to ask the question!

Welcome to the forums.

The brushes are usually mounted on springs that hold them tight against the rotor. The brushes wear in an arc pattern around the rotor. As they wear, the springs expand and loosen.

The motor fails to start because the arc-pattern wear gets too deep and there isn't enough spring tension to hold the brushes against the rotor. When the motor spins, the springs can move slightly to one side and allow the brushes to make contact.

Hand-starting it won't work for too much longer. I agree with Ray (and your initial instinct): Replace the brushes.
 
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Old 11-15-10, 12:55 PM
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Thanks guys. I agree...at $0.89 each, two of those won't break me to satisfy my curiosity. Thank you Rick for the basic education on the brushes. This issue has launched a good learning experience for myself and my boys. We'll report back once we get the brushes in.
 
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Old 11-15-10, 01:03 PM
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And if you feel like taking it apart....cleaning the commutator (where the brushes rub) with emory cloth won't hurt.

And hopefully the brushes can be had locally...the shipping can be a bear.
 
  #6  
Old 11-15-10, 02:14 PM
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I noticed that area seemed "dark" for a lack of better terminology. Thanks for the suggestion Gunguy...I will do that if possible. I don't know the shipping yet but I figure it will be a gazillion times the cost of the brushes...yet another part of the learning experience for my boys!
 
  #7  
Old 11-15-10, 02:37 PM
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Sometimes you can get at it easier with a disposable nail file trimmed down to be pretty thin.
 
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Old 11-15-10, 05:00 PM
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If I use the nail file option, do I just place the file flat on the commutator and turn the motor while applying light pressure?

This might be the better option as I think taking the motor apart is not possible without partial destruction (not sure right now as the motor is not with me). Is there anything else to be considered?

Thanks to everyone for the replies...I appreciate it
 
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