Assembling your Coffee Cup Stirling Engine Kit
Cylinder Assembly

4) Position the Crankcase so that it is upside down: you can use two empty soup cans for this purpose.

5) Insert the Rod portion of the Displacer assembly into the hole in the bottom (now top) of the Crankcase.

6) Position the Cylinder Ring [D4] on the bottom (now top) of the Crankcase so that the Displacer is evenly centered. This is the position in which you will glue the Cylinder in a moment.

Do not use Loctite or Super Glue when connecting the Cylinder to the Crankcase or the Cylinder Cap.

Remove the Displacer assembly while leaving the Cylinder in place: be certain that the Cylinder does not move. Carefully mark a pencil line around the inside of the Cylinder. Remove the Cylinder and re-insert the Displacer to verify that the pencil marks are correct (and uniformly outside of the displacer). You should be able to just barely see the pencil line outside of the in the following photograph (especially on the right edge of the Displacer).

Now apply adhesive to the Cylinder using one of the following techniques.

7a) Method using silicone caulk:

After removing the Cylinder, apply a small bead of silicone caulk to the edge of the Cylinder, as shown below. Too small a bead and the seal may not be air tight; too large a bead and there may be excess silicone squeezed out of the seal (which is unsightly but not damaging). Note that you should not apply adhesive with the Displacer or Cylinder in this position show below (you might get adhesive all over the Displacer and the Crankcase): this is just for illustrative purposes.

With the Displacer removed, carefully press the Cylinder onto the bottom (now the top) of the Crankcase. Be careful to center the Cylinder in the pencil line you have drawn on the Crankcase. The seal must be air tight, so be sure that the sealant is applied evenly. Gently twist the Cylinder back and forth 1/2 inch to ensure an air tight seal. Set aside to set/dry. This is what the Cylinder looks after it has been glued to the Crankcase with silicone.

7b) Method using epoxy:

The best way to get neat results with epoxy is to apply a ring of epoxy to a piece of paper. Place the Cylinder on a piece of paper and draw pencil lines on the inside and outside of the Cylinder.

Mix the epoxy on a separate area of your paper, then generously apply it between the pencil lines. Now gently press the Cylinder down into the epoxy and rotate the Cylinder Ring 1/4 of a turn, applying the epoxy to the Cylinder. If you press too hard, you may not have enough epoxy remaining on the Cylinder.

Remove the Cylinder from the paper and gently place it on the bottom (now top) of the Crankcase.

Rotate the Cylinder to spread the epoxy around evenly. Check for air bubbles between the Cylinder and the Crankcase. Add more epoxy as necessary to ensure an air tight seal. Set aside to set/dry.

8) Check that the Cylinder Cap [D5] is flat. Place the Cap on top of the Cylinder with the lip pointing away from the Cylinder (i.e., the reverse of how it would normally be installed) and inspect it for gaps. Gently bend the Cap as necessary to get an even fit.

9) Insert the Displacer into the Crankshaft, as shown below:

Review the next two steps carefully before proceeding.

10a) Method using silicone caulk:

Carefully apply a thin and even bead of silicone caulk to the bottom (now top) of the Cylinder.

Carefully press the Cap onto the Cylinder Ring. Rotate the Cap slightly to ensure an air tight seal. Check that the Displacer can still move freely and has no adhesive on it. Leave the Crankcase upside down until the cap has set/dry (to ensure that the Displacer does not drop down and get stuck in excess adhesive).

10b) Method using epoxy:

Epoxy must be applied with the engine right-side-up, to ensure that no epoxy drips down the side of the Cylinder and touches the Displacer. The Displacer must be kept up (tight against the Crankcase) while the adhesive on the Cap sets. To do this, cut a 1.25 inch (3.2 cm) piece of Rubber Tubing and slide it onto the Displacer Rod and slightly over the Brass Tube which projects out of the Crankcase. You may find it easier to do this if you first wet the Tubing (inside and out) with rubbing alcohol. In the image, below, note that the Displacer is tightly up against the Crankcase and that the Tubing is stretched over the Brass Tube.

Apply epoxy to the bottom of the Cylinder, using the paper technique described previously, and carefully press the Cap onto the Cylinder. Rotate the Cap 1/4 turn to ensure an air tight seal. Be careful that the Displacer does not slide down and get into the epoxy near the Cap. Do not continue assembling the engine until the epoxy has stopped being tacky: this may take much longer than the stated setting time. Set the engine aside (right side up) to set/dry.

Set the Crankcase Assembly aside to right side up (as shown below not above) to set/dry.