Caterpillar Diesel Powered Mobile Welder

A 1955 Caterpillar-Powered Lincoln Welder

If you hear the word “Caterpillar,” your first thought is probably a bulldozer. However, you might be surprised to know Cat built engines for marine and industrial purposes as well. In 1955, they branched out to service the welding markets with a unique unit.

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The full story is unclear, but late in 1954, plans were made to produce a welder powered by a Cat engine. Cat engineers teamed up with Lincoln Electric in Cleveland, Ohio, to produce a powerful 400-amp welder powered by a Cat D315, four-cylinder diesel. They called it the Cat Twin Arc-Welder because it placed two 300-amp, 40-volt NEMA Lincoln generator heads end-to-end behind the Cat engine, with a souped-up 1.5 KW exciter to run them both. Generally, the unit was intended to allow for simultaneous operation of two welders using up to 300 amps each, but by bridging to the two units together and running them in parallel, Cat rated it for 400 amps.

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The welding unit has two sets of controls for each 300-amp head. If you can’t get the job done with 300 amps, you can add some bridging cables and run them in parallel for 400 amps. It isn’t clear why you can get the full 600 from doing that, but what do we know?

Even though he has had a career in welding, current owner Mike Schreiber had never seen a rig like this. That’s been true of pretty much anyone else who has seen it. Mike, a well-known Caterpillar collector and restorer, is well-versed in Cat products, but this rig was a bit of a mystery. He contacted both Caterpillar and Lincoln and learned that the D315 engine powering it was built in May of 1955—the same for a companion welder found at the same time. The generator head was one of a 19-unit order from Lincoln built around the same time. Cat produced a brochure and a parts book, but it seems this welder was not a hot seller. A later version, built in 1963 with a D311 engine, was found recently, but the model relationship to the earlier unit is unknown. The generator head and welding controls are largely the same, but it uses the later D311 engine. So far, just three Cat Twin Arc-Welders are known to survive.

The working history of Mike’s welder is unknown. When found on a farm, it had been sitting 22 years with the twin unit. Both wore decals from the Contracting and Material Company, of Evanston, Illinois. This company did all sorts of large and small construction jobs in the Midwest during most of the 20th century, but it apparently went out of business in the 1980s. A search found only a few references to it online.

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The head of the oversized exciter sticks out of the cable end, but again, you can see the welding lead connections for the two welders. It’s here that you would bridge the two heads to get more than 300 amps. The unit still had the remnants of the Contracting & Material Company decal, so Mike had it reproduced to offer a little historical context.

After bringing the welder home in 2015—looking as derelict as could be—Mike found the engine in good condition and had it running in short order. The welder had issues, but during the restoration, the generator was sent off to a specialist for internal repair and it now works well. The sheet metal was Swiss cheese, so a good portion of it had to be recreated. It took a while, but Mike eventually found a few period pictures of similar units. A few differences in the sheet metal deepened the mystery. If you happen to know anything about these rare, mid-’50s welders, get back to us and we’ll pass your info on to Mike.

Just so you know: we didn’t come up with the “Hot Rod Lincoln” title—Mike did. Of course, it goes back even farther into Rock ‘n’ Roll, car-song lore, but to have such a big-and-powerful old welder that nobody has even seen leads to some fanciful names. And, yeah, it welds great!

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The welder was based on the D315 power unit/generator. This engine had debuted in 1947 and was used in the D4 crawler/dozer, 355 Traxcavator, and 112 Motor Grader. It saw service though 1959 before being replaced by a new engine. It displaced 350 cubic inches from four 4.5 x 5.5-inch cylinders. Flywheel output was a maximum of 82 hp at 2000 rpm, but the welder was rated for 1800 rpm and about 68 hp—the same as the 40KW generator set. The engine used wet sleeves and had five main bearings with 3.5-inch main journals. It had a compression ratio of 18:1 and was indirectly injected using pump and injectors designed and built by Caterpillar. The D315 cranked over with a 2-cylinder, 10-hp-at-3000-rpm gasoline pony motor, and that had a standard rope starter and an optional starter generator.

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