A spot welder is a necessity for the production of a homemade gas turbine, unless you can accurately and easily TIG weld a LOT of very fine stainless steel, on the order of0.5 mm. Commercially produced spot welders have several things wrong with them... first, they are rather expensive, typically $250-$500 U.S. Secondly, the welding tips, where the actual fusionoccurs, are relatively thick, and difficult to squeak into tight crevices like the bottom of a combustion chamber. They are also mostly hand-held devices, which would make the spot-welding of small partschallenging. So I guess if I was welding up a bed frame, a commercial welder would suit, but not a 2" dia. combustion chamber.
Thus, the need for a custom spot welder. Desireable attributes are a highquality, repeatable weld, ease of use, and low cost.
All of the parts for this welder (except the transformer) are available from MSC. The transformer must be scrounged from an electronics/industrialsurplus outlet. Look for a BIG 115VAC transformer (700 Va or better) with the secondary windings on the OUTSIDE. Listed below are MSC parts numbers, and current prices.
An overall viewof the completed welder. Plans were "created" on the spot, using knowledge gleaned from the internet on such a project. The basic concept is to find a big 115VAC transformer which has the secondarywindings as the outer layer. The secondary is carefully (but tediously) removed, and replaced with enough coils of #4 copper cable to create a secondary voltage of ~4 VAC. a DeStaco clamp is adaptedfor the upper arm, while the lower arm is fixed, but insulated.
A closer view of the modified transformer. After the secondary was removed, there was enough room for 5 turns of #4 copper,insulated cable. You can use welding cable, or you can cannibalize the cable from a set of automobile battery jumpers. Be sure it is heavy #4, and flexible enough to wrap around the transformer.