How to Build a Stirling Engine


A Stirling engine drives a piston by heating then cooling air inside a leak-proof container. Heating the air causes it to expand while cooling it causes the air to contract. As air in this version of a Stirling engine heats, the piston goes down due to the expansion of the air. When the air cools, the piston returns to the up position when marbles roll toward the hotter air.

  • Lay a piece of wood flat measuring 11-by-3 1/2-by-1/2 inches, and connect two pieces of wood measuring 6 3/4-by-1 1/4-by-1/2 inches at either side of the midline of the larger piece. The bottom of each smaller piece should align with the bottom side of the larger piece.

  • Screw through the outside of the smaller pieces of wood to attach them to the sides of the larger base piece. Keep the edges flush.

  • Reinforce the frame of your Stirling engine with a piece of wood measuring 3 1/2-by-1 1/4-by-1/2 inches. Attach this piece between the two upright pieces of the frame about 2 inches up from the base piece. Screw the reinforcement piece into place.

  • Place five marbles into a test tube and place a rubber stopper with an aluminum tube attached into the opening of the test tube. Fit the aluminum tube with a 1 1/4-inch long piece of soft surgical tubing, and put the other end of the tubing onto a glass syringe that holds up to 3ml.

  • Stretch a rubber band around the tops of the side pieces of the frame for your Stirling engine. Place a heat source such as a short candle or an alcohol lamp at one end of the base board and use two-sided tape to stick a rubber mat measuring 1/2-inch square in the center of the opposite end.

  • Stick the flat end of the syringe to the top of the rubber piece with two-sided tape. Hold each side of the rubber band and cross them over each other. Place the test tube through the hole formed by this twisting motion and let the rubber band fit around the middle of the test tube.

  • Light the candle or lamp and allow it to heat the marbles inside the test tube. As the marbles heat, they roll toward the cooler end of the tube and cause the syringe to contract itself. As the marbles cool and roll back toward the heat, the syringe expands.

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