Instructions for a Stirling engine

Preliminary remark to the building instructions

Stirling engines work with two pistons, one displacement piston and one working piston:

• The displacement piston is located in a container that is heated from the outside. This can be a gas flame, a candle or just a cup of hot coffee. On a large scale, a Stirling engine can also be used with solar heat.
• When the container is heated, the piston inside the can rises and can drive a flywheel via a crankshaft. At the same time, the air above the displacement piston is pressed into a working piston that is sealed with a diaphragm or a factual bellows.
• The crankshaft pushes the bellows or the diaphragm back down, with the air above the Displacement piston escapes back into the container and the displacement piston is again lowers.
• The piston moves up again due to the heating and the process starts all over again.
instagram viewer


Hovercraft: building instructions to build yourself

Of course you will not get any building instructions from Hovercraft, after all, beware ...

These building instructions will help you to build a Stirling engine.

Construction of the displacement piston of the Stirling engine

For the Stirling engine, choose a metal lid that can cover a cup well and tightly. Cut a 10 cm thick disc from an acrylic glass tube with a precision saw.

1. Attach the cylinder to the metal washer with silicone. It must stick absolutely tightly to the metal lid.
2. Cut out a circle from a styrofoam ceiling board that is big enough that it can move easily in the cylinder.
3. Glue a plastic drinking straw exactly in the middle of the styrofoam circle and put the piston in the cylinder. Test whether it can be moved easily.
4. Drill a hole in the second lid through which you can put the drinking straw. It should be able to move easily, but still sit tightly in the lid.
5. Cut another hole in the lid that is about 2 cm in diameter.

Instructions for the rest of the Stirling engine

1. Cut an approx. 5 cm long piece and close one side by securing a piece of a balloon with adhesive tape. It has to be absolutely tight.
2. Mount this part onto the larger hole in the lid using silicone. You are now almost finished with the Stirling engine.
3. Glue 2 round pieces of wood onto the cover and a strip with a recess that fits the axis that you use for the flywheel. This axle bearing must sit at right angles to the axis between the working piston and displacement piston. And so close to the drinking straw that it is perpendicular to the axis of the flywheel.
4. Now use a wooden disc and a wooden stick to make an axis onto which you stick a CD. One side of the axis must be flush. Drill a hole there next to the axis and insert a piece of a wooden stick into it. The other part of the axle must be longer and be weighted down with an attached washer that sits above the working piston. Place the axle in the axle box.
5. Divide the straw and connect it using wire eyelets that you have bent from thin wire, and attach the straw to the crank with a wide eyelet (wooden sticks next to the axis).
6. Glue a second crank to the washer, this must be exactly opposite the first crank in relation to the axis, otherwise the Stirling engine will not run.
7. Attach a wooden disc that is able to press down the membrane to another drinking straw and attach it to the second crank with a wire eyelet.
8. Your self-built Stirling engine should run after a short start, as soon as it sits on a mug with hot liquid.

Troubleshooting and Variations

• Instead of an acrylic tube, you can also make the cylinder from offset foil or laminating foil that has run through the laminator once without paper.
• The motor looks nicer when the bearings are made of acrylic glass and the rods and axles are made of metal.
• If the engine is not running you will need to change the thickness of the displacement piston by removing several washers from the styrofoam cut, enlarge or reduce the working cylinder by tensioning the membrane differently or by hanging it loosely permit.

You will certainly have to experiment a little, because even the best assembly instructions rarely lead to the Stirling engine running straight away.