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#51 Geary Carrier

Geary Carrier

    all there...???

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Posted 24 December 2017 - 03:57 PM

Duralco 4461...Oops. This was the first time I've ever used this epoxy and I should have degassed it first. Other than curing full of air bubbles it worked well wicking into the windings and Kevlar. I need to do a bit of experimentation with this epoxy.

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Yes, to be sure, this is it...





#52 havlicek

havlicek

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Posted 26 December 2017 - 06:36 AM

OK!  Now I have another element to look at.  I haven't been cleaning the coms prior to winding, this may be my turning point.  I'm still gonna turn on some classic rock though, minus the headphones lol!

John, the whole process of brazing the com tabs relies on current passing through the tab and out the associated com segment.  For the current path to work, there are two points on the com (the tab and the segment) where a good clean connection are critical.  Sometimes a little dirt or other non-conductive "stuff" on the tab or the com segment can stop the current from passing for a second...until it DOES suddenly pass with a "POP" (*as Geary said).  That "POP" is a split-second arc, and an arc is an amazingly efficient com-destroyer.  BTW, the silver/flux paste stuff I use is NOT a good conductor.  If you use it on the com tab (*along with some silver wire), you need to make sure it's not on the tip of the com tab where your brazing rod will make contact.

The other thing that can happen here because of a poorly cleaned com is for the current to pass through a different com segment (*if you're using a clamp on the com that contacts more than one segment) and then through the magnet wire looking for "the path of least resistance".  This can and will burn up an entire armature's coils PDQ.  If the tab and the com segment are clean, current will find the com segment you WANT it to pas through as "the path of least resistance", avoiding that whole problem.

***Because just "age" (*if you're using vintage coms) can cause enough tarnish/oxidation, or the manufacturing process can leave residue to prevent the copper from conducting electricity well, some sort of cleaning/prep of the com and com tabs before brazing is really important for the brazing deal to work well.


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John Havlicek

#53 Geary Carrier

Geary Carrier

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Posted 26 December 2017 - 06:11 PM

Received my little toy from Bill Bugenis. Got readings of .064, .064, .066.

Thanks Bill...

 

I only polished the comm as I don't have a cutter yet and I'm not sure how much cutting the comm will make in resistance measurements.

I'm going to leave the epoxy as is and send the arm out for grinding, balancing and comm cutting.

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Yes, to be sure, this is it...


#54 havlicek

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Posted 27 December 2017 - 06:01 AM

Received my little toy from Bill Bugenis. Got readings of .064, .064, .066.

Thanks Bill...

 

I only polished the comm as I don't have a cutter yet and I'm not sure how much cutting the comm will make in resistance measurements.

I'm going to leave the epoxy as is and send the arm out for grinding, balancing and comm cutting.

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Sweet Geary!  Cutting the comm can oftentimes even out small differences in resistance readings, even when the comm is clean.  ***Most importantly, cutting the com should cut "brush bounce", and the associated arcing it causes way down.  That will make for a cooler, faster, smoother running motor that draws less current as well.  The "Champion" type 36D comms have wide com slots, so truing up the com should also help with brush wear.


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John Havlicek





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