Date: Sun, 14 Mar 2010 22:13:17 -0700
From: jimlux <email@example.com>
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.
> 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
360 degs. No load Vdc was aprx 30 vdc. Forget what size wire was used. It
175' run.. or 350 ' loop.
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