Hot Air Engines at the 2017 Coolspring Show

More than 200 hot air engines, fans, toys and models made an appearance at the Coolspring spring show.

hot air engine

Dr. Brent Rowell's large F.F. Slocomb & Co. hot air engine features two walking beams to connect the power and displacer pistons.

Photo by Woody Sins

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It may seem unusual for a museum dedicated to the preservation, display and education about internal combustion engines to consider featuring external combustion hot air engines at their annual show, but that is just what the Coolspring Power Museum did for their spring show on June 15-17, 2017. In doing so, the museum recognized the contribution this type of engine made to the industrial revolution, and the show was a great success thanks to the excellent cooperation and hard work of the Coolspring Power Museum’s volunteer staff.

Hot air engines

Hot air engines are a category of external combustion engines that operate on the alternate heating and cooling of a mass of air in an enclosed space. The resulting raising and lowering of the air pressure is used to drive a power piston. Hot air engines, available before the internal combustion engines had come onto the scene, offered a low cost, low power alternative to the steam engine then in common use. They are capable of using any sufficiently hot source for heat, and had no boiler to give trouble and maintain.

Unfortunately, the metallurgy and low power output made their use quite limited. Although some hot air engines were used for very small power applications, like small power tools and such, by the dawn of the 20th century most hot air engines in use were only being used to pump water and operate as fans in remote locations. Hot air engine toys were popular at the time, and to this day, machinists and experimenters continue to build models of both classic and more modern designs.

In total, 201 hot air engines, fans, toys and models were on hand for the event. About 56 full-sized engines, from the diminutive Essex engines made in Buffalo, New York, to an enormous Ericsson pumping engine with a 10-inch bore, were scattered within the buildings and throughout the grounds. Thirty-seven antique fans were on display, with the balance being toy engines of various vintages, plus beautifully machined models. These exhibits, along with the many fine and unusual engines on the grounds and on display in the museum’s buildings made for a show that was not to be missed.

Dr. Brent Rowell, a noted historian of the Rider-Ericsson company, wrote a brief but thorough history for publication in the museum’s Bores & Strokes and put on an excellent presentation of the company for interested enthusiasts. For the most part, the weather cooperated, with only a few passing thunderstorms to mar the proceedings. Collectors came with their engines from all over the East Coast and Canada, and visitors from as far away as Europe and Australia came to see the museum and the show.