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Assembly day is almost always non-eventful


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#1 havlicek

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Posted 23 October 2016 - 07:32 PM

The operative word there is "almost." Anyway, I have a pile of motors to assemble with arms back from grinding/balancing. The first five went smooth with no big hassles (well, I was out of the springs I wind for the Mabuchis, so I had to make a little side trip to spring-winding land).  

 

Then I got to an old Mura NCC12 where I used the old arm/stack and comm after stripping, to keep as much of the original DNA as I could. I did the same stock wind, left the timing in place, the only difference being that I had the arm balanced and a light "skin" grind done. No matter what I did, the motor runs warm and draws more current than it should. It runs smooth, but just doesn't run well, and I tried all sorts of things with no change.

 

So... it goes back into the "drawer of parts." Sometimes a motor just doesn't want to be built.

 

-john


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John Havlicek




#2 boxerdog

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Posted 23 October 2016 - 09:16 PM

Sometimes I have seen this caused by a bad brush or brushes. 


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David Cummerow

#3 havlicek

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Posted 24 October 2016 - 05:50 AM

Hi Dave,

 

     I had that happen to me this past year, so I checked the motor with several pairs of brushes.  I tried springs, recutting the com, checked the arm spacing to make sure it wasn't being pulled to one end or the other.  The arm meters perfectly too.  Matter of fact, since the original "12" arm was unbalanced, untied, unepoxied, this one should have run much better.  It DID run smoother, way smoother, just not "well".  You say to yourself "well, it's not some sort of voodoo curse, there must be some easy explanation", but I just ran out of things to check and got too ticked off to continue wasting time on it!

 

-john


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John Havlicek

#4 Eddie Fleming

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Posted 24 October 2016 - 07:15 AM

I have a 12 motor that I could not figure out why it was running hot on the PS. Changed springs and brushes and checked everything. no help.

 

It turns out the magnets had been reversed and it was running backward when I hooked it up normally.


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Eddie Fleming

#5 boxerdog

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Posted 24 October 2016 - 09:28 AM

Hi Dave,

 

     I had that happen to me this past year, so I checked the motor with several pairs of brushes.  I tried springs, recutting the com, checked the arm spacing to make sure it wasn't being pulled to one end or the other.  The arm meters perfectly too.  Matter of fact, since the original "12" arm was unbalanced, untied, unepoxied, this one should have run much better.  It DID run smoother, way smoother, just not "well".  You say to yourself "well, it's not some sort of voodoo curse, there must be some easy explanation", but I just ran out of things to check and got too ticked off to continue wasting time on it!

 

-john

I know what you mean, I've been there too. In a few cases, I smashed the motor in a vise so that the problem would never repeat itself! Sometimes logic does not prevail. 


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David Cummerow

#6 havlicek

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Posted 01 November 2016 - 06:05 AM

Ha Dave...that's one way to solve the issue!  :D

 

-john


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