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Re: [TowerTalk] Fw: Prop Pitch Motors

To: <>
Subject: Re: [TowerTalk] Fw: Prop Pitch Motors
From: "Jim Hargrave" <>
Date: Fri, 23 Oct 2009 08:57:42 -0500
List-post: <">>

I can't answer your question directly, but I would suggest that the voltage
is not a big issue as long as you do not exceed the 10 Amp rated running
current. I would install an ammeter in the line and run some test.

Here is my experience/setup.

I am using a Prop Pitch rotor on my TH6-DXX and 14 el 2M beam. Mine is the
small one perhaps like yours. I have had this same rotor for the past 40
yrs. I originally had it on top of my 50ft. tower and had approximately a
75-80 ft run from the power transformer to the rotor. I used standard 12
gage Romex for the power. I have always powered my rotor with AC using a 24v
battery charger transformer with a variac on the primary. With this
arraignment the variac was normally set to about 75% for normal rotation.

When I moved to my current QTH about 13 years ago, I installed the rotor 4
ft from the bottom of the tower and use a water pipe up through the tower to
mount the antenna. I use cable suspension on the drive shaft and do not have
any thrust bearings. The pipe just goes through the sleeve at the top of the
tower. With the cable suspension there is no weight on the rotor, making it
easy to remove for maintenance, should I ever need to. I will say that this
has been a very reliable rotor. In the 40 yrs, I have never had to remove it
for repairs. However, I have had it at 3 different QTH and have serviced it
each time before installing it.

I installed a wx proof box near the base of the tower and installed the
transformer/variac in the box and remote control it via relays from the
rotor controller. My Rotor power lines are now only about 3 ft and the
variac is set to 50% for Summer operation and 55% for winter when the rotor
grease is cold. Its also very easy to maintain at this level. At Age 75, I
don't climb anymore.

To avoid the oil from seeping down into the motor, I removed the oil and
installed a grease Zerk on the side of the case and filled the gear box with
light weight lithium grease. No more leaks. The only drawback is in cold
weather the rotor is a little slow, hence the reason I jack up the voltage a

   * 73's Jim W5IFP *

   >-----Original Message-----
   >[]On Behalf Of w2lu
   >Sent: Thursday, October 22, 2009 1:51 PM
   >Subject: [TowerTalk] Fw: Prop Pitch Motors
   >----- Original Message -----
   >From: w2lu
   >Sent: Wednesday, October 21, 2009 2:35 PM
   >Subject: Prop Pitch Motor
   >I am using a "small" prop pitch motor to rotate a 7-50 Mhz LP
   >(15 ele on a 45 foot boom).The power supply (about 24 VDC) was
   >at the top of the tower (100 feet). I recently burned out the
   >bridge rectifier and decided, since I'm not as fond of climbing
   >as I was a few decades ago, to move the power supply, relays,
   >etc. to the base of the tower. I have run a three wire (two
   >plus ground) "burial " cable (12 guage) from the motor to the
   >base of the tower. I figured about 0.5 ohm at about 10 amps
   >would give five volt drop so I wanted 30 VDC at the base of the
   >tower. This gives me not more than 1/4 rpm. It was about 3/4
   >rpm with the 24VDC PS at the top of the tower. How  much
   >voltage should I dare put on it? Other possible problems like
   >rusty bearings (Yeasu mast bearing, or inside the PPM), worn
   >brushes and /or commutator (new brushes and turned commutator
   >with only 3-4 years light service) possibly caused by oil
   >leaking down from the gear box,
   >   Since it's basically working, hopefully there's just more IR
   >drop than I calculated - 200 foot round trip of #12 plus a
   >couple of sets of plug contacts and connections into the motor.
   >I just don't want to make things any worse by going too high
   >with the voltage. What does the VDC/RPM curve look like?
   >Gene / W2LU
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