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Subject: [TowerTalk] WHICH ROTOR TO USE?
From: "Jim Thomson" <>
Date: Tue, 8 May 2012 04:44:16 -0700
List-post: <">>
Date: Sat, 05 May 2012 20:17:52 -0400
From: K8RI <>
Subject: Re: [TowerTalk] WHICH ROTOR TO USE?

The Orion 2800 was one of the other rotators I was trying to think of 
which I believe uses a double worm gear drive and pulse direction 

###  The OR-2800  does NOT  use a double worm gear drive.  It’s
just a single worm gear drive.   While the upper clamp on the OR-2800
may well look massive and heavy duty, its junk, toss it.  The teeth will
not bite into anything, esp  heat treated chromolly steel or DOM. 
Replace it  with either the clamp assy from K7LXC... OR the
one from kurt Andress, K7NV.   The one that Kurt makes for
the OR-2800 is the same design as what he uses for his prop
pitchs.  IE: they pinch the mast almost a full 340 degrees.  The surface
area is just massive  vs the tiny amount used on the teeth of the oem

##  The OR-2800 control box is fubar..although it works.  The GH
box blows it away hands down.  

The Canadian built, AlphaSpid is a great rotator that I believe fits 
inside a 25G has rotational torque of 3200 inch# and holding torque of 
14,000 in #
Price was roughly the same as the Ham IV with a digital control box or 
about $1200. With the current exchange rate I'd guess it to be some 
where between $1400 and $1500. OTOH I've not heard much about them for 
a while. They are "I believe" sold stateside by MFJ.

##  My understanding is the Alpha Spid is built in Poland,and that Don
Morman, VE6JY, owner of Alpha radio, is just the importer and distributor
for them.   MFJ is now the US distributor. 


## here is a list of dealers world wide.

##  exchange rate is at par  between US and Canada.  If you are in the usa, you
may as well buy one from mfj....and cross your fingers. 

##  I would take all these rotating torque numbers with a grain of salt, since
most are pure BS, when actually measured.   We have all sorts of nonsense, 
from...  start up torque, running torque, stall torque, braking torque, etc. 

##  the prositel  numbers are not real.   If you look at any of these rotators, 
start up current in the motor is easily triple the running current.  Hence the..
start up torque numbers they quote  are much greater than the running
torque number.   That high start up current only last 1-3 seconds when you 
measure it. 
As noted, the upper and lower casings shoulda been welded
together, instead of using 4 x  tiny machine screws.   They went cheap on the
power xfmr.  It may well be an issue of using a 60 hz rated xfmr on 50 hz...
which will surely cook it. 

##  brake wedges  are steam engine technology.  The T2X is rated for
1000 in lbs =  83 ft lbs of torque.   1000 divided by 12 = 83.   83 ft lbs
is  miniscule.   The ham-4-5   is even less, at  just 800 in lbs = 66 ft lbs.
These are toy rotors at best.  Potentiometers  are passe these days. A buddy 
has replaced
several of the bournes pots in his protistel PST-61. 

##  If you folks intend on turning a big array, at least try and torque balance 
ant in the array, with either a counterweight....And-OR  a torque compensation
plate.  That is all explained on kurts  site.    I used his software to design 
several of them
with great success.    One fellow tested his hb 20m yagi  with and without the 
TQ plate
on a short tower, with NO rotor..and in a high wind.   With the TQ plate done 
right, the yagi
will NOT windmill in the wind.   With out the TQ plate, it will literally bust 
the wedge brake 
and then rip the gears apart in his T2X.   

##  The 83 ft lbs of TQ  pales in comparison to the 1250 ft lbs of TQ  from
a small prop pitch  from k7nv.   The small prop pitch + mating GH box
+  k7NV  super mast clamp is the ultimate solution.  GH makes  a special
version of their box, made esp for the K7NV Prop pitch.  Kurt has
modified the PP, so it uses digital pulses  from the magnets he installs. 
It uses a hammond xfmr inside the GH box..for the PP...and only outputs
one dcv. 

##  The mast clamp that K7LXC uses for the OR-2800  is for a 2 inch mast
only.  The K7NV version is  for a  2 inch mast also...and he also makes a 3
inch version and any other mast od you want to use, like 2.875 inch, etc. 
They work, because they are designed  for one OD of mast.   My 2 inch OD
x  .375 inch thick chromolly mast just barely slides into the k7nv clamp
assy.   You barely tighten the 5 x bolts, and it pinchs the mast so tight,
it will never slip on you. 

##  The GH box is slick, like having a 9 speed automatic transmission
in a car.  Starts off slow, then ramps up to full speed... whizs  over to 
Europe, then starts the slowing down  ramp down.   You wouldn’t put
your car into park..while driving  down main street, so  don’t do it on
a  rotor either.  

##  whatever size rotor you buy, go one size up, and don’t go cheap.
If you destroy it, then you have to spend $$  to fix it, then spend even more
$$$  to buy the bigger rotor to handle the job.  Or  expect  a repeat 
of the destruction on your rebuilt rotor.  Wind pressure goes up to the
SQUARE of the  wind speed.   A 70 mph wind is DOUBLE the impact pressure
of a 50 mph wind.   And a 83 mph wind gust  is  TRIPLE the pressure of a 
50 mph wind.   Any gust only has to last just a few seconds to rip an
under rated rotor apart. 

##  You will  save  nothing buying a small rotor, trust me.  

Later..... Jim  VE7RF


Roger (K8RI)

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