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Old 11-27-2009, 02:26 AM
dragon5126 dragon5126 is offline
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Quote:
Originally Posted by phreak97
thanks for the reply,
I had the commutator machined not too long ago, and it continued to eat through my brushes, the spring tension is good, and the brushes are new (again), my regulator is adjustable with screws to move the points closer or further apart, how do I go about setting the adjustment?
dont be afraid I wont understand something, I've worked with electronics for most of my life.
Hey Phreak, I'm a retired Electonics Engineer (career three, colleges took A LOT of my income), and grew up spinning a wrench. First the commutator... Sometimes machining it just doesnt work as it has wore beyond useful life. The smaller it's diameter the greater the lagtime btween the brush being in contact with more than one of the contacts which is the base cause of arcing and carbon build up. the second thing with the commutator is was it machined right? It isn't a simple matter of turning it on a lathe, bevels need to be cut on each side of the contacts, first to ensure a clean area, second to reduce the time that your brushes spent on two contacts at once, the greater this time is, the more arcing that occurs, just as you notice in an old well worn electric hand drill. A good shop will also rebed these contacts with a good epoxy such as acraglas to ensure none break loose, and to ensure proper insulation between each and every one. SADLY, this is a dying art, in this day of throwaways and factory only rebuilding, really messsing with those of us who use or need the proper parts. On to your regulator, one forum member posted the most probable problem, that being misadjusted contacts. HOWEVER knowing how many of these contact were designed, I can tell you that carbon buildup can also be caused by contacts that are beyond their lifespan. These were typically domed silver or silver clad contacts, the silver was used as it minimized arcing and silver oxide and silver both have identical resistance/conductance characteristics. When the contacts wear flat (or are filed instead of burnished, which is a form of mechanical polishing that doesnt remove metal) A greater area where arcs form develop, and the more arcing that happens, more metal is burned away, reducing reliable contact area (think relay bounce characteristics) leading to more carbon build up and cascading arcing conditions. Hopefully with your knowledge and this information you can come up with a suitable cure for your problem.
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