On 9/6/11 1:53 PM, Gene Fuller wrote:
> Hi Jim -
>
> In defense of the PPM's - Have you ever opened one up and seen how
> they're built ? I would guess that any motor shop could rewind the
> "coils". The bearings and brushes are obtainable. The gear box, if
> tended to, should last forever, or at least have replacements available
> for longer than any of the current rotators will be supported by their
> manufacturer or NEMA. They may be an overkill for many of the jobs
> they're asked to do, but my guess is that they will outlive most of us
> who are using them.
Oh yeah, I've seen the insides (and Kurt has lots of pretty pictures on
his website) they're pretty standard motors and gear boxes and I'm sure
you could get it rewound, refurbished, etc. You could probably even get
replacement gears, although some of the internal components and the
housing isn't a "stock" item. (I had to replace a gear in a horse
hotwalker that used some old Ford transmission, and there was a place
out in the San Fernando Valley called "gears R us" or something like
that and sure enough, they had an exact replacement for a 50+ year old part)
But, they do go beyond the point of repair eventually, or otherwise
permanently be removed from the market.
If you had a design which used standard motors and standard gearboxes
(e.g. with C-face mounting), then you can get a replacement literally
anywhere. The only "antenna unique" part would be whatever mounting
brackets hold it to the tower and whatever couples the mast to the
gearbox output shaft, and those aren't exactly what you'd think of as
"wear out-limited life" components.
You could publish a drawing and have any machine shop make it (sort of
like the "open hardware" designs you see).
It's sort of like flathead Ford engines.. it's possible to keep one
running, but at some point, you're better off switching to something
newer, even though you could probably keep making replacement parts forever.
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