[TowerTalk] Fw: Prop Pitch Motors

[w2lu]

----- Original Message ----- 
From: w2lu 
To: towertalk at contesting.com 
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