The Under-mounted Aultman

History of The Aultman Co.'s Under-mounted Engine is Still Being Written Despite Obscurity and Failure

| July/August 2004

  • Threshers Engines
    Cover of the 1904 The Aultman Co. general catalog, describing 16 and 22 HP Double Star engines.
  • The Aultman Engine & Thresher Co

    Chicago branch house
  • 16 HP engine

  • Aultman engines

  • # Picture 01

  • Avery under-mounted engine
    An 18 HP 1908 Avery under-mounted engine at the 1984 Central States Threshermen's Reunion in Pontiac, Ill
  • Under-mounted engine

  • Under-mounted engine


  • Threshers Engines
  • The Aultman Engine & Thresher Co
  • 16 HP engine
  • Aultman engines
  • # Picture 01
  • Avery under-mounted engine
  • Under-mounted engine
  • Under-mounted engine

Sometimes, owning a particular engine prompts a collector to delve deeper into the history of a particular manufacturer. With nearly 50 engines having come and gone over the years, I've learned a lot about many different companies, but sometimes the information I received was incomplete.

Before I got my under-mounted Star from Bob Lefever, Lancaster, Pa., I thought all under-mounted Stars were 22 HP, but I soon would have reason to doubt that. When I acquired my engine, I pulled the cylinder heads off to inspect the cylinders.

I had two Aultman catalogs at the time: A 1904 Aultman Co. special catalog introducing the under-mounted engines and a 1906 Aultman Engine & Thresher Co. catalog. For no real reason, I had ignored the 1904 catalog and used the 1906 catalog for reference. I had been told (it was even in Jack Norbeck's Encyclopedia of American Steam Traction Engines) that my engine was 22 HP, which I had no reason to question. Using my 1906 catalog as reference for specifications, I set my micrometer to 7-1/8-inch to check the cylinder bores, but the gauge wouldn't fit into the cylinders. Assuming I had made a mistake or miscalculation, I checked the catalog and the gauge again, and it still didn't fit the bores measured 7 inches even.

Confused by this, I checked the engine's other dimensions against the 1906 catalog and found that nothing matched, not even the size of the boiler tubes. I began to wonder, 'What is this engine?' Then I remembered the 1904 catalog. I dug it out of my files, and sure enough, every dimension of my engine matched the specifications listed. My 22 HP engine was suddenly a 20 HP engine.



A letter issued with The Aultman Engine & Thresher Co. 1906 catalog by the Chicago branch house. The Aultman Engine & Thresher Co. was formed to liquidate the assets of The Aultman Co. following its bankruptcy in 1904.

That made my engine older than I thought, as the 20 HP engines preceded the 22 HP engines in Aultman's advertising. I knew that L.E. Mazilly, Starks, La., once owned an under-mounted Aultman with a lower serial number than mine, so I dug out an old photo of Mazilly's engine. On the back, Mazilly had written, '22 HP, 7-inch-by-10-inch bore and stroke,' along with serial no. 6766. I try to avoid assumptions, but I had to conclude that Mazilly's information was as limited as mine. If his engine really had a 7-inch-by-10-inch bore and stroke, and considering its earlier serial number, then it must also be a 20 HP I have not seen that engine or measured it, so I will say at this point it is 'probably' a 20 HP engine.