This Rider Ericsson hot air engine was built by Roger Butzen of Texas, and loaned to the Miniature Engineering Craftsmanship Museum as part of the Engine Collection of Paul and Paula Knapp. The small engine is 11”-long, 5”-wide, 11”-high, and weighs just 4 lbs. A hot air engine uses the expansion and contraction of air under the influence of a temperature change to convert thermal energy into mechanical work.