Introduction: Rotating LED Throwies Driven by a Stirlingengine (eVoltis Stirlingmachine)

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About: My name is Volker. I live near Osnabrueck (Northwest-Germany). My profession is an electrotechnical engineer. I like to go on journeys and take many photos of interesting places.
This is a hot-air machine (stirlingengine), built with some old computer-parts (heatsink and the head of an old harddisk). This Stirlingengine (and all others also) works with a temperature difference between the hot bottom side (e.g. heatet with a candle) and the colder topside (cooled with the heatsink of an old 486 CPU) of an metal can (e.g.hairspray).
Simplified the engine works as follows: The candle heats up the air in the tin can. Hot air needs more volume. While we have a nearly constant volume in the tin can, the pressure rises up. This will affect, that the main-piston moves up. Coupled over a simplified crank, a second auxiliary piston (inside the can and so big, that his volume is nearly half the volume of the can) moves down. So the hot air moves from the bottom side along the big piston to the topside with the heatsink. It cools the hot air so that a vacuum occurs and the main piston will be drawn down. Now the auxiliary piston moves up and the cold air moves from the upper side to the bottom, were the candle heats it up again. This will occur solang, as the temperatur difference between the top and bottom side is great enough.

But now lets go. Have fun with this instructable.


Step 1: The Main Material

At first go shopping and buy canned-beer, coke, peanuts or something else which is useable as a container.

You see, its not really important what kind of can you prefer.

ATTENTION: ALL DIAMETERS are in mm (Millimeter). 1 mm is 0.03936996 inch
The raster of the paper in some pictures is 5mm

Furthermore you need:
2 Lithium CR2032 cells (3V) and 2 LEDs .
A pipe (brass or aluminium) with an approx. diameter of 20 mm and a length of 40 mm. I used an old chromed pipe from a shower (that part, where the shower-head was mounted).
An old CPU heatsink.
The head of an old harddisk.
Bare wire (1.2mm) and a drill also 1.2 mm
Wire 0.8mm (elctronic equipment)
U-profile alumnium 20 mm x 7 mm x 100 mm.
2 component epoxy cement (coldmetal stick) or normal 2 component epoxy glue.
A small piece of styropor/styrofoam.

Step 2: The Tools

Screwdriver,
Flat nose pliers.
Round nose pliers.
Scissor.
Wire cutter.
Drill machine.
Drill bits.
Tape.

No special tools.

Step 3: The Can

The can I use has a diameter of 50 mm. If nesessary, cut the lenght to 100 mm.
You have to generate a really good and straight cut. For this job I used a metal cutting disc.. Be careful. At least smooth down the edge.

Step 4: The Auxilliary Piston

This piston is inside the can. It's made of styropor/styrofoam. The height is approx.. 40 mm (a little bit less than half of the can's length) and the diameter is 5 mm less the can's diameter. You can form it with a sharp knife or with a hot wire (constantan). See the pictures.

For the piston-rod bend a 1.2 mm blank wire as shown in the picture and apply it to the piston. Fixate it with a piece of tape. For heat protection, wrap the piston with aluminium foil.

Step 5: The Cylinder -part 1-

For the cylinder we cut a piece of 40 mm from the brass pipe. Smooth down all edges and the inner side of the pipe. The inner side must be very very even, I used toothpaste for the last finish.

We make the piston of epoxy, with this cylinder as the form. For this, oil the inner side very well.
Then place it on baking paper.

Step 6: The Main Piston

Cut a piece of 10 mm from the epoxy cement and knead it very well (~ 1 minute) until the epoxy has a homogene colour and gets a light warm. Fill it into the cylinder and compress it with a wooden staff (which must be oiled before using).
When the glue is hardened, press it out from the cylinder (use the wooden staff). Use a hammer and hit the wood carefully. It's not so easy, but it works.
Now cut the uneven Part of the piston with a saw. Smooth down the piston and the cylinder very well. Smooth down the piston so long, until it moves very easy in the cylinder.

It is very important that the piston easily moves in the cylinder and seals this, nevertheless, very well.

Drill a 1 mm hole across the bottom side of the piston. Attach a 0.8 mm wire with two isolation parts (for centering). Don't forget the piston rod. This is made of 0.8 mm wire. At the ends make a very small loop with the round nose pliers. The length over all is 60mm.

Step 7: The Cylinder -part 2-

If available, use a little piece of copper-clad Pertinax (electronic equipment). Drill a 5mm hole in it. Solder the pipe with a soldering iron on the copper-clad side of the Pertinax.
Then solder the whole cylinder the same way.

If you don't have Pertinax, you can use a copper or brass sheet.
You can also use other stable materials and connect the parts with glue (e.g. epoxy).
The temperatures at the cylinder will not increase very high.

Step 8: Preparing the Heatsink and the HDD-head

Drill a 1.2mm hole exact in the center of the heatsink. This is the hole for the auxiliary piston-rod. This rod is made of the 1.2mm wire. If you use a new drill, normally its diameter is a little bit greater then the nominal value. My 1.2mm drill was exactly 1.25 mm. So the rod can move easy and is also tight enough.

(My first hole was not good. So i make a bigger (5mm) hole in the center of the heatsink. Then i close this hole with the epoxy-cement. When its hardened, i make a better 1.2mm hole.)

Drill a second 4.9mm hole near the egde and press the little 5mm brass pipe into this hole .

Make two loops from the 0.8mm wire and fixate it at the heatsink.

Drill a 1.2mm hole across the axis of the HDD-head (see picture). The head is made of aluminium.

Step 9: The "crankshafts"

For the two crankshafts bend the 1.2mm wire as shown on the pictures.

Step 10: Assembling the Parts

1. Attach the gasket to the heatsink. Double-sided adhesive tape may help you.
2. Put the auxiliary piston into the can.
3. Mount the heatsink with the 4 screw/wire combinations to the can. If you won't disengage this connection, you can glue the can direkt to the heatsink (in this case you don't need the gasket and the screw/wire combinations). Take care, that the rod with the auxiliary piston moves very easy in the heatsink hole.
4. Mount the cylinder to the brass pipe of the heatsink. Blow into the cylinder, to check that the construction is tight!
5. Connect the U-Profile to the heatsink.
6. Connect the HDD-head with the U-Profile.
7. Mount the main piston-rod and the crankshaft together.
8. Put the piston into the cylinder.
9. Crimp the wire of the crankshaft a little bit, so that it get stuck in the 1.2mm hole of the HDD-head.
10. Connect the second crankshaft (auxiliary piston) also to the HDD-head. The angle between the crankshafts shall be 90 degree.
11. Connect the rod of the auxiliary piston with a thread to the crankshaft.
12. Solder this construction (see picture) to the main piston crankshaft.
13. Now your sterlingengine is ready!

Step 11: More Pictures of Some Details

Attached you find more pictures of some details. Maybe this makes some things clearer.

Step 12: Your Sterlingengine Is Ready !

Now work is done. Create a simple stand for the engine, place a little candle under the bottom and the engine will run. If not, investigate that all is tight and the rod and the piston moves easy.

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