DIY-Welder - Build your own Arc, MIG and TIG welder

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The first prototype proved the board worked and the alternator could generate enough current and voltage for welding. It took up a lot of space and the old mower was badly rusted. it would have taken a lot of work to strip down, sand prime and paint it. I wanted something more like a portable generator.

Major components:

• Craftsman Riding Mower Frame
• 12 HP Briggs and Stratton Engine
• Custom control board
• Hand-wound reactor
• 3 x 23,000uf/75V capacitors
• Motorcraft 200A alternator
• 1/2" alternator pulley
• Main drive and ideler pulleys from riding mower.
• Ignition switch
• Battery
• Gast tank, approximately 1.5 gallons from riding mower.
• Charge/discharge ammeter
• Tweco-compatable output terminals (turned on lathe.)
• Throttle control cable from riding mower.
• Kill relay
• Sheet metal from old combo washer./dryer.
• 1" x 1" x 1/8" angle iron

I started with the frame from another riding mower:

The 18HP was nice, but it was huge. I opted for a 12HP engine that ran well and fits better within the frame. 1" angle iron for frame. Tank and battery sit in the top.

Left is the control panel and output terminals; 3/4" conduit used for handles. Right image is the pully setup underneath for the alternator. The idler in the middle makes the belt cover a longer angle around the pulleys. That helps prevent slipping. The upper idler is spring loaded.

Here's all the parts installed for an initial test. Yes, the wiring is a mess ;). There is a reactor coil at the center with 2 large capacitors. This helps smooth the arc and provides easier starting in arc mode. The caps also help it delever the large surge needed in short-arc MIG welding. Test welds show the 12HP had plenty of power for up to 3/32 rods. It should be able to do 130A on MIG.

Almost done. Side panels made out of sheet metal cut from an old clothes dryer. Just needs final top cover and paint.