[TowerTalk] Prop pitch motor.

[Jim Thomson]

Date: Sun, 14 Mar 2010 22:13:17 -0700
From: jimlux <jimlux at earthlink.net>
Subject: Re: [TowerTalk] Prop Pitch Motor


Gene Fuller wrote:
> What is the maximum DC voltage used successfully/recommended for one of the "small"  PPM's ?  What speed was accomplished and how was the brush life at that voltage ?
> I 'm building a power supply to put at the base of the tower and can change the voltage from about 30 to 48 volts in 6 volt steps. Cable to PPM will be 100 feet of 3-#12's. I'm figuring about 0.5 ohms and about a ten amp demand  i.e. a 5 volt drop.
> Any suggestions will be greatly appreciated.
> Thanks,
> Gene / W2LU

Handy to remember..

AWG 10 wire is about 0.1" in diameter and 1 ohm/1000 ft.

For every 3 gauges, the resistance doubles.
For every 10 gauges, the resistance is x10.

So.. 200 ft of AWG 10 (up and back) would be 0.2 ohms.
Going to AWG 12 is a bit less than doubling (0.4 ohms)

Your estimate of 0.5 ohms for AWG 12 is a bit pessimistic. (assuming a 
single conductor up and back)

If you were thinking triple AWG 12 up and triple AWG 12 back, you'd be 
much less than 0.2 ohms total, since 3 AWG12s is almost twice the cross 
sectional area of a single AWG10.

##    3 x 12 ga wire in parallel =  9 ga wire. =.8077 ohms  per  1000' 

##  200' loop   = .16154 ohms.   With 10A... V drop =  1.6154 V 

## dunno abt DC motor's  but start up current on small AC motor's is   typ 
3 X  the  running current.   I have measured several small ac motor's.. and typ
measured 3.1  X  the running current. 

##  I had a small prop pitch motor back in the 70's.  It was 1 min, 50 secs  to do 
360 degs.   No load Vdc was aprx 30 vdc.  Forget what size wire was used. It was 
175' run.. or  350 '  loop. 

Jim   VE7RF