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From: cas@mtcchi.uucp (2668-Charles A Sherwood(Z550900)0000)
Newsgroups: sci.electronics,rec.autos.tech
Subject: homemade welder
Summary: converting generator to welder
Keywords: converting surplus generator to welder
Message-ID: <1990Oct10.180843.27630@mtcchi.uucp>
Date: 10 Oct 90 18:08:43 GMT
Distribution: usa
Organization: Memorex Telex Corporation NSBG/STP
Lines: 47

Hello people

Is there anyone out there that has build a welder using a surplus aircraft
generator. I have acquired a 400amp 30 volt aircraft generator and I am
considering building a welder out of it. 
Burdens Surplus also sells surplus aircraft generators for this purpose
and they provide plans, which I have a copy of and it goes like this:


	|------------|
     ||-|generator   |A-------------arc stablizer--------
	|------------|	   |				 work
	   |	 F	   |			   gnd---
	  Gnd	 |	rheostat
		 |	   |
		 -----------


The rheostat is used to control the welding current.
The arc stablizer prevents the arc from burning the generator's brushes
and provides a smooth weld.

This has lead to a few questions. 
1) Is it worth all the effort? Will it work as well as a regular welder?

2) An arc stablizer is a large coil of wire. Burdens sells them, but can
   I make my own? What is the correct wire size? How much wire is needed?
   What is it wound on? Iron or air core?

3) How much horse power is required to drive the generator? If I use a 
   5HP electric to drive it(5hp motors are cheap and available). 

   	5HP x 746 watts/HP = 3730 watts

   Assume 70% generator efficiency, 
	3730 x .7 = 2611 watts.
   	2611 watts /25 volt = 104 amps of welding current. 

	IS this enough?? or is a larger drive motor required?
	A larger electric drive motor would not be cost effective.
	A 7.5HP single phase electric motor retails for about 400, 
	which would by a nice welder, with accessories.
	A 8HP gas engine would be an alternative, but is a little
	noisy.
		8HPx 746 x .7 / 25 = 167amps (more than enough)

chuck sherwood