This Plunket atmospheric gas 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. Mr. Butzen’s Plunket engine is 17”-long, 12”-wide, 8”-high, and weighs 17 lbs. An atmospheric gas engine is one of the simplest forms of internal combustion engine, using a mixture of air and gas drawn into the cylinder. The engine uses atmospheric pressure to create a partial vacuum, which forces the piston up and down.