Date: Tue, 06 Sep 2011 14:51:03 -0700
From: Jim Lux <jimlux@earthlink.net>
Subject: Re: [TowerTalk] Heavy Duty Rotor
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)
## The prop pitch's came in 4 x sizes..not 3. I have the small k7NV
PP..and mating
green heron control box...and that combo is superb. I also own a pair of new
OR-2800's...and that would not make it to the short list for turning both a
large
3-el 40m yai + 6 x el 20m yagi. They don't have enough torque...and the
stock mast clamp
is semi useless. If you replace the stock OR-2800mast clamp with a K7NV mast
clamp... [he makes em for
the OR-2800, in any diamter you want]..then at least you end up with a proper
mast clamp.
## The protistel rotor's are pretty good....except for most of their mast
clamps. They all have the same
problem, not enough surface area. This is cause the mast clamps they use will
handle a range of diameters,
instead of one exact OD.... like the K7NV mast clamp. If you have ever seen
a K7NV mast clamp... you will
see right away that it's the...'real deal'. The K7NV mast clamps have loads
of surface area...and picnh the mast with
almost a full 350 degs. The smallest k7NV PP has globs of TQ vs the
OR-2800, no comparison. Regardless of which
rotor you end up with, the green heron control box, imo is the best control box
on the market, simple, easy to use, and works
with any rotor, has point and shoot capability..and also ramp up andf down.
## A buddy tried turning a new 4 x el 40-10m monster stepir....with a new
OR-2800..and the Or-2800 self destructed
after just 9 x days! The only thing being turned was the monster IR... and
yagi was just above the top of the tower.
## The infamous Alpha Spid is made ....[if I have the story correct] in
Poland...and now come in 2 x sizes. The bigger of the
two might work out ok... as long as the mast clamp is up to the job. If your
gonna try and turn a 40m yagi and a 6 x el 20m array
you really want a 2.875" DOM mast or a 3" 4130 heat treated chromolly mast. A
2" 4130 chromolly mast will also work, provided
it's at least >100 ksi yield strength..and at least 3/8" wall thickness. A
2.875" or 3.00" mast with a 1/4" wall..will weight the same
as a 2" OD x 3/8" thick mast... BUT the larger diam mast with the thinner wall
will be a heck of a lot stronger. You can see that asap
by using any of the popular mast programs..like the free arrl one.
Later...... Jim VE7RF
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