[TowerTalk] Ramp up

[K7GCO@aol.com]

In a message dated 11/8/00 1:41:15 PM Pacific Standard Time, K7GCO writes:

<< Dennis:  In addition to the simple way to ramp the voltage I gave below 
and suggesting some drag in the gear box, I have another suggestion that 
might be causing the slower speed.  The commutators can get dirty and should 
be cleaned.  A dirty commutator will slow it down.  Also my Variac suggestion 
that I use myself, it feeds the 110 AC input to the transformers that provide 
the 28 VDC. 10 amps or more is not uncommon.  A higher voltage at the shack 
can make up for the resistance of long lines.  That eliminates running other 
power lines up the tower for the transformer and relays there.  This and my 
"Stepped Voltage Switch" described below to provide a stepped voltage for a 
smoothing up and down on the speed is so simple and functional that any other 
system is going to be very complex.
 
 Any style motor is easy to get apart. There are 3 right angle bolts holding 
the end bearing plate where the brake is that are a bit tricky the first 
time.  
 
 One style of motor is easy to get off the gear box as it's just bolted on 
the small gear box as well as the large gear box.  Another style of mounting 
has a big retaining ring that can be hard to break free.  I'd spray around it 
with WD-40 and let to soak.  Secure gear box in a vice. Take a chisel with a 
blunt end and use a big hammer to turn it on the square notches of the ring 
CCW.  If that doesn't do it, heat it and use a jack hammer.  Even then that 
can be a hassle and I almost gave up on one but on the last series of hits, 
it came loose.  Grease the threads when it's reinstalled.  
 
 I'd sure check out the gear box.  There is another trick you have to know to 
get it back together if you remove the planetary gear or you won't get it 
back together.  There are witness marks or a number like "0" on the rotating 
gears that has to be positioned out or the bell gear won't slip on.  In any 
system everything has to be right for proper operation.  Everything has to be 
checked when you have a problem.  When everything is properly prepared for 
rotator use, I've checked several PP motors after 25 years and they didn't 
need any maintenance except I did clean the commutator.
 k7gco
 
 In a message dated 11/7/00 9:51:42 PM Pacific Standard Time, K7GCO writes:
  In a message dated 11/7/00 1:02:57 PM Pacific Standard Time, 
dcoolica@planet.eon.net writes:
  
  << drive a prop pitch rotator with a 90 volt DC motor.
   I was wondering if anyone had any circuits or devices for controlling a
   DC
   Motor.  I want to control the ramp up and ramp down on a motor driving
   the prop pitch on the 5 element 20 meter beam.  I want to bring it up to
   full speed in 5 secs and then, when I turn it off, I want it to slow
   down in 5 secs.  That way I do not have sudden starts and stops.
   I don't want to reinvent the wheel again, unless I have to.
    Anything on this kind of stuff for this homebrewer. 
    Denis Ve6AQ / Ve6FI
    >>
  Dennis:  It's very simple.  Use a Variac for smooth up and down.  Or have a 
series of filament transformers connected in series for a stepped voltage.  I 
speed up all rotators mechanically and have a switch for the stepped voltages 
starting from some minimum slow voltage with voltage steps that are 
comfortable.  Switch points up on 0 voltage and progressive steps up and then 
back down on each side for CW and CCW.  The small TV and normal Ham rotators 
I speed up to 4 or 5 RPM so the stepped voltage (about 1 RPM each step) is 
easy on them. 
  
  I have a neat way to mechanically speed up prop pitch motors and have done 
it to all that I have. I may put out a book on how to do it.  The most 
important thing is to make sure no water can get around the spline gear.  I 
have drain holes for the recesses and the holes on the side of the housing 
have to be plugged.  The 3" top bearing on the small PP motor can't be 
obtained anymore and it rusts if water gets by.  I have a way to regrind it 
for larger balls but it takes some time to do it. All other bearings are 
available or can be cleaned, repaired and new balls easily.  I use a drain 
hole in the bottom of the gear housing.  I use a synthetic grease on the 
gears.  It's called AM's Grease.  It doesn't get stiff in the cold.
  
  I run a lot of F/B checks and I can't stand a slow rotator.  The PP Motor 
the best rotator around.  All the others need all kinds of "band aids" to 
keep them going.  Properly installed I recommend checking the PP motor at 
once least every 50 years. 
  
  What's the story on the motor you use?  Where does one get it?   K7GCO >>
  >>

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