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[TowerTalk] Prop Pitch Motor

To: <>
Subject: [TowerTalk] Prop Pitch Motor
From: "w2lu" <>
Date: Wed, 21 Oct 2009 14:35:34 -0400
List-post: <">>
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 dcades 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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