[TowerTalk] Ramp up

[K7GCO@aol.com]

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 propitch 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 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.  It's 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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