LTD Stirling engine





Step 8: Make the cutter for the displacer

* There's a different tin can in the photo's, you should use the same size tin as you used for the top
and bottom of the engine.

Take a tin can and cut around the rim(Fig 23a) so that you have a clean edge (Fig 23b).

Fig 23a: Cut the rim of the can off

Fig 23b: Clean up the edge


Now drill a hole in the tin can and thread in a bolt or screw (Fig 23c), this is just to use as a handle to move
the hot tin can.

Fig 23c: Insert a bolt or screw as a handle.


Step 9: Make the displacer

The displacer is cut from 10mm polystyrene, you can buy this as ceiling tiles or just cut it yourself using
a wire cutter (Fig 24a). Heat up your cookie cutter using an electric hob(Fig 24b) or similar and press it into the polystyrene.
It should cut out nice round, slightly tapered displacer parts.


Fig 24a: Polystyrene, 10mm thick

 
Fig 24b: Heat up the tin can


After you've cut them out, they should look like Fig 25a. Glue the two halves together using epoxy.


Fig 25a: Cut out polystyrene

Fig 25b: Glue them together

Finally, sand the edge little to take the edges off (Fig 25c).


Fig 25c: Sand the edge a little

Step 10: Drill an air hole through the lid:


[DRILL AIR HOLE THROUGH THE LID..... I forget to do that
, I had to drill it later, very awkward!]

No picture yet....

Step 11:  Epoxy the top lid into the displacer cylinder

Push the top tin can into the displacer cylinder until it's about 5mm from the top edge of the lowest curved parts(Fig 27a).
If it's loose and keeps falling out, you can bend the edges of the can out slightly by running the back of the knife around the edge of the tin (Fig 27b).
 
Fig 27a: Fitting the top can in place
 
Fig 27b: Do this if it is a little loose


Apply the epoxy to behind the bottle lid first (Fig 27c), turn it on its side and let the epoxy run down the side, as it's difficult to apply it in such a tight place. Then epoxy around the rest of the edge(Fig 27d), making sure that you fill all of the gaps. Any air leaks and the engine won't run.


Fig 27c: Apply epoxy

Fig 27d: Seal all around the edge


Step 12: Fit the displacer rod.

Put the polystyrene displacer into the displacer cylinder (Fig 28a), and make sure that it is centred.
Then, take the brass rod out of the displace bushing jug that you made earlier, and push it through the bushing
and through the displacer (Fig 28b).


Fig 28a: Fit the displacer into its cylinder

Fig 28b: Push the brass rod through

Remove the rod, and sand a indent in the bottom of the displacer (Fig 28c).
Re fit the rod, and epoxy it in place (Fig 28d), using the indent you just made.

 
Fig 28c: Make a well for the epoxy

Fig 28d: Apply epoxy

Step 13: Make the cranks

The cranks have two arms which are set at 90* rotation apart. The first one is for the diaphragm to connect to.
It should be bent out around 3mm (Fig 29a). Make sure that the two ends of the cranks spin in line with each other.

For the next part, measure the distance between the displacer and the end of the cylinder (Fig 29b). Deduct about 2mm
and half that number, this will be the displacer stroke.


Fig 29a: First crank arm

Fig 29b: Measuring

Now bend the displacer crank arm, it iss bent at 90* rotation relative the diaphragm arm. If you lay the
diaphragm arm on the table, the finished displacer arm should point to the sky (unless you're a bat).

Fig 29c: First bend of the second crank arm

Fig 29d: Finished cranks

You can thread the cranks through the plastic bearing and give it a spin (Fig 29e). It should be extremely
easy to spin. Cut the protruding end to size, the left side needs to be about 50mm long (Fig 29f). You can attach
the flywheel (the jig for the bushing) and see how it spins.


Fig 29e : Thread the cranks through

Fig 29f : Trim the cranks

Step 14: Bend the displacer rod above the bushing.

Test the displacer, to make sure that there is not too much friction. Lift the displacer up, it should
fall under its own weight easily. If it doesn't, there must be too much fiction somewhere, you need to find
the source of this.

If it is OK, you can bend the rod over just above the bushing (Fig 30a).

When that's done, you can add the diaphragm, which should be a little loose (Fig 30b)


Fig 30a: Bend the displacer rod over
Fig 30b: Fit the diaphragm


Step 15: Make the connecting rods and attach them.

Fig 31a: First loop of the displacer rod
Fig 31b : Make a zig zag


Fig 31c: line it up

Fig 31d: Loop it around the cranks.


Fig 31e: Wrap the wire around the bolt
Fig 31f: Make a zig zag


Fig 31g: Attach it to the bolt.

Fig 31h: Wrap it around the cranks

Step 16: Epoxy the bottom tin on.


Fig 32: Seal the bottom tin in place
 


Step 17: Attach the flywheel

To attach the flywheel, bend the end of the crank over and tape it to the cardboard.

Fig 33: Attach the flywheel.

Step 18: Add a counter weight

Tape a 5p coin onto the cardboard, on the opposite side that the displacer crank arm is pointing to


Fig 34: The counterweight.

Step 19: Finished !

Hopefully your engine will zoom up to 100 RPM straight away, but if it doesn't, don't despair.
Check for air leaks by submerging the engine under warm (50c ish) water. There will be a small
amount leaking through the displacer bushing, this is normal.

If the engine is airtight and it still doesn't run, there's probably too much friction. There's not much I can say about
that other than fiddle around with all of the push rods, sometimes getting a better alignment between all of
the parts will help considerably.

Remember, this engine is made from very low temperature materials, don't expose it to any more heat than
that off of a cup of hot/just boil water!



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