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Everyone knows: for the work of a table fan, you need an electrical network or at least a battery. But not always.

The fan was made by students of the technical school of the Japanese engineer Koishi Hirata.

This stirling is powered by hand heat.

Candle powered fan

...and this one needs a cup of coffee to work

The device is very elegant from a technical point of view and is by no means useless. You can take it on a hike and put it in a tent, use it in a house on a garden plot where there is no electricity. If we also take into account that a third of humanity today lives with kerosene lamps, then a fan powered by a candle must have a huge market.

The fan motor consists of two cylinders. One of them, let's call it the main one, is a flat cylindrical box. Its bottom is heated by a candle, and the top cover gives off heat to the surrounding air. The lid and bottom are made of metals that conduct heat well, such as copper or brass.

The cylindrical wall connecting them is made, for example, of materials that conduct heat poorly, such as glass or plastic.

A power cylinder is mounted on the cover, the piston of which, by means of a connecting rod, is connected to one of the crankshaft cranks.

Inside the box there is a foam displacer. Its rod is connected to the second crank of the crankshaft. Both of these cranks are located at an angle of 90° to each other.

Fan device: 1 - propeller; 2 - crankshaft; 3 - displacer connecting rod; 4 - clutch; 5 - connecting rod; 6 - power cylinder; 7 - bushing; 8 - displacer

Here's how the engine works. Imagine that at the first moment the piston of the power cylinder is at bottom dead center (1). In this case, the displacer, connected by means of a connecting rod to another crank, will be in the middle position.

The air below it will heat up and expand. This will cause the piston of the power cylinder to rise up, doing work (2). The displacer at the same time will begin to move to the extreme upper position, and the heating process will go even faster.

Soon the power piston will reach its top dead center (3). The displacer will again be in the middle position. (Note that almost no work is expended on its movement, because the air, thanks to the gap, freely flows around its edges.)

When the displacer is at the bottom (4), air cooling through the top cover of the cylinder will begin. The pressure will decrease and the piston will start moving towards bottom dead center. And so without end. The most difficult part of the engine is the main cylinder of two plates, tightened with bolts and nuts, between which a plastic ring with a diameter of 120 mm is sandwiched. It can be cut off from a mineral water bottle. The edges of the ring must be perfectly even and parallel to each other, otherwise you will not achieve tightness of the cylinder. (In order to neatly cut off the ring, it is better to make the simplest cutting device shown in the figure.)

The principle of operation of the Stirling engine

The lower and upper plates - the covers of the main cylinder - are best made of brass or aluminum with a thickness of 1 - 2 mm. It is not worth using steel, especially stainless steel, because of its low thermal conductivity.

Each cover has six 3mm bolt holes and the top has two additional holes. One is for the sleeve through which the displacer rod must pass, the other is for installing the power cylinder.

As a sleeve for the cylinder rod, you can use a piece of pencil from which the graphite rod has been removed. Take a short knitting needle as the displacer rod.

If its diameter is larger than the diameter of the hole, make a so-called "cannon drill" out of it. Put it in a drill and at low speeds drill a hole in the bushing. If this work is done carefully, you will get a hole in which the stem will move easily, but with almost no play. Graphite from a pencil can be used as a lubricant.

Cutting off a ring from a plastic bottle

Cannon drill and its work

Making a piston without the help of a lathe: 1 - power cylinder; 2 - tin insert

Scheme of the simplest foam cutting machine: 1 - 12 / 220V transformer with isolated secondary winding; 2 - nichrome wire

Make a power cylinder from a piece of brass sleeve from a hunting rifle cartridge. If the cover is brass, then the sleeve can be soldered to it. If aluminum - solder a tin flange to the sleeve and screw it to the cover with self-tapping screws.

It is better to turn the piston on a lathe, but if there is no machine, you can solder it from tin. To do this, cut off a strip of tin and stretch it several times around a smooth rod. As a result, it will acquire elasticity and the ability to curl up into a spiral. Insert two pieces of such a spiral into the sleeve and, gradually pushing it out, solder the seam in it. Solder the lid to the resulting cylinder, sawdust, drill a hole, and you will have a piston.

Cut the displacer out of the foam using a hot nichrome wire. (Nichrome can be taken from an old soldering iron.) A diagram of a device for making a displacer is shown in the figure.

The piston and the displacer rod, as already mentioned, are connected to the crank using connecting rods.

The crankshaft is bent from steel wire. It is mounted on tin racks. At one end, attach a suitable propeller. To avoid longitudinal shift of the shaft, put on it couplings with screws from the children's constructor.

Author: L.Ilyin

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