[TowerTalk] Heavy Duty Rotor

[Jim Thomson]

Date: Tue, 06 Sep 2011 14:51:03 -0700
From: Jim Lux <jimlux at 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