This 2-cycle rodless rotary engine, suitable for aircraft or autos, is a prototype built by Peter Grunstra. It’s a running 138-cubic inch prototype; however, no production engines were ever built from this design. Mr. Grunstra donated the engine along with various patterns, castings, extra parts, and a complete set of blueprints to the Miniature Engineering Craftsmanship Museum. Read an article about the rodless rotary engine. Additionally, you can view a copy of the original patent. This engine is not currently on display.