Re: SER1 Horn Bracket

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Nick your a gem....what memories you bring back....

An instructor I had "old Fred" showed us how to undercut with and hack saw
blade side ground for thickness, then machined a commutator flat and said go
to
it....needless to say there were a few ugly gouges on the copper but after a
while
it was easy.....one key also was the copper segements were tappered as was
the insulation
I seem to recall depth was 1 x width of insulation....and too deep a cut was
equally as bad
as too shallow which Fred was all too happy berate us about.....we used to
wrap
"chux super wipes" around the hack saw blade then use insutlation tape to
hold
it there so as not to cut our hands up.....in fact I still have one from 25
years ago.....
24 tpi blades were the go.....

The other thing we did is if we couldn't solder the armature wire in place
we cut a slot
in the copper commutator segment and placed the coil wire in it (stripped
the insulation off of course)
and used a small punch to press/ cold weld the wire in place...worked a
treat...

Bruce



> Bruce is absolutely right about commutators.
>
> Much fuss was always made about the proper undercutting of commutators.
>
> If the insulating mica/synthetic is proud of the copper as the copper
wears
> the brushes bounce off the insulator and a large part of the contact area
is
> lost - arcing takes place and the copper is eroded but the insulator is
not.
> This makes things worse and worse. It may cause weak operation or if you
are
> very unlucky the arcing burns out a commutator bar or heats it up enough
to
> spit out some of the soft solder that connects the bar to the winding and
> then the whole thing fails.
>
> I bet most modern shops do not have the skill, patience or the special
tool
> to undercut an old style commutator as newer types do not have this
problem
> as a different design/material is used.
>
> If you want sore hands then follow the old advice - grind down the
thickness
> of a hacksaw blade and use it to do the undercutting - It has to be just
the
> right thickness to remove all of the insulator and none of the copper.
> Steady hands are needed too.
>
> Nick.
>
>
>
> To change subscription see www.landrover.net/series1/mail
>
>


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