Ceramic Stirling engine.1

Today is just a try for to make at home with domestic materials. In this page we would like to finish a model where you can make it and put on running. For the moment this blog is in construction and with the next months we continue adding more information of how to build it. Almost you know that  you do, it's recommendable to follow the guide for not lose time and breaking forty pieces like the author did some time ago.



For the moment we only have this video from Youtube.




As you can see in the formula, the power we can get in a domestic engine with normal pressure and low temperature difference result in a power  low.
Design your own machine here

Backgrounds.  

From scratch, our goal was to create a model like this, projected for to make it in steel and capable of to reach  800 rpm. In fact, it's very similar to the popular solar beta engine you can find anywhereThe model appears ideal due to be a beta engine, medium size and certainly cool. The chance of to create without lathe and the fact of there isn't tries in the technique at the moment were our incentives.

                                                                                                     A model template made in cardboard.
  Crystal engine

In this experiment with this machine with a glass tube and pistons made it of aluminum and epoxy. The model almost run but with fire and the cooling with water. Nevertheless due a failure mine, in one moment a drop of water fall in the glass and broke it. I don't continue with this model because the glass tube is very expensive where I live and this model is very distant of to be a ceramic engine.



The materials.

Clay. 

 -Clay is cheap, very easy of to manage and you can find it in everywhere and you can make small pieces without have a furnace, firing it in small fire with coal.


The clay allows you to reach a 800ºC of operating in a machine but is a little fragile and some forms are difficult of to get due to the shrink, around a ten per cent of average.


To reinforce the clay with steel is useless and the tensile strength is very low, above all when we make the piece and fire without furnace and it's very difficult to make tiny items.It surface is very smooth.

Generally this material would be great for to make in a homemade engine, the cooling fins for instance, a ball bearings box or a ashtray. For a displacer cylinder the best is to buy a model already made it, like a cup of coffee, beaker, etc.


Concrete.

Concrete made with Portland cement is a mix very popular and it's price is in the average. We can make strong pieces with the help of steel for to reinforce and molds always the items don't have to support high temperatures up to 150ºC.
This is very suitable for a nice flywheel, a engine frame...





Refractory mortar.

Ideal for be in contact with the fire, you can get in market for to operate to 750ºC. Nevertheless, It usually a  weak material and wrinkled. It's very hard to make a piece with it. It use is for to cover surfaces or fill some pieces against the fire.

                                                                                             In the photo, a example of heat-resistant cover.

Glass.

This is our main good for to make the cylinders, pistons, capable of to bear 800ºC, it surface it too smooth. The main trouble is to can cut it.
But you can read some easy methods in internet. Be careful cause not at all glass resist the heat and is very easy to break and hurt oneself.





Other materials.

The are other small figures items, that due to its size we can't make it, like the rods, crankshafts. All is because the low tensile strength of the ceramic goods. In that case we must to get steel, plastics epoxi, etc. However if you are privileged you will be able to build it with glass if you have the tools for it.




Furnace homemade.

For the pieces made in clay, we need to fire it, if we want that it become hard and solid. For that we have 2 options:

-Cover all the pieces with coal and light on, this method is very fast and we can use for small pieces though is likely that some piece be broke.


-Build a furnace with a hole in the bottom, fill it with the pieces to fire and sawdust. Put the can slightly on the floor with two bricks or something for the air can circulate down of it. And once the fire is on, cover the top with some that resists the heat. Hope 8 to 12 hours to get your pieces.
Extras:
If you want to increase the temperature of your furnace that already is great, cover the can with refractrory bricks and substitute the sawdust for coal. Anyway you shouldn't light on the fire with alcohol, cause its flame is unseen and the danger of to fire oneself is enormous. Always use the articles appropiated for it you can find in any supermarket.

Things to consider.

A beta engine is a concentric machine where the dead space is low and that result is a major efficency. However due our machine is homemade and that means, being sincere, the friction and the bad sealing are our enemies. But we can to get some tricks for the stakes and almost achieve the machine runs.

First.

It's mandatory to minimize the  friction at the minimum value.

Second.

The volume ratio between the displacer and power piston may be almost 3:1.

Third.

It's desirable a considerable lenght of the connecting rods, althought this decrease the speed of our machine, it help to start the machine.



THE ENGINE FRAME.

The engine frame is one of the most important pieces and its solidity is essential for the machine. One of the most fast ways for to made one is with steel and concrete.


The first step is to create 'the armature" with the typical steel grid that you can obtain in any specialized shop.

Note that the armature have a big hole in one face where the cilynder is fitted and there are two small holes in the sides for to set the crankshaft axis.

The following is to cover the armature with concrete, the thickness of concrete should be about near of one centimeter. Helping us with tables and paper for to cover the big holes and the walls. Don't worry for the small holes for the screws, we'll make it later. Wait 2 days for to quit the assistants, 7 for the emeril and 14 for to make holes with the drill.

At the end, with a ceramic varnish we can have good view of the item.         

COOLING FINS.

For this element, the best and more cheap is make it in clay. The way of to do is the next; first we get a bunch of clay and with a roller we create a table smooth of clay , in a flat surface covered with fabric. And with the help of small ruler we can leave the  loaf of clay very plain.

The second step is make the outer circle with a big can like mould and a knife for to cutting the clay. The inner diameter must be something more big than our displacer cylinder, cause the clays shrinks, remember.Use a cylinder or some more bigger than the original cylinder. Furthermore we must avoid work with the clay very humid for unable the fissures appearance. The third step is  create the cylinder that join the discs. All the steps should be make in a hour or so and glue the parts of clay with slip and assure that the union is perfect. Don't worry for the mistakes due you be able to repair when the clay is dry easily with a knife. Wait 2 days at least for it. About of the sixth of seventh day you can fire the piece in a small fire with coal during 1 hour, (although you don't have furnace, you can fire it covering with  abundant coal). but start the fire with the clay for to prevent the strong changes of temperature that can destroy our piece, a pre-fire at 200ºC  in a domestic oven is ideal too.The clay generally must reach 800ºC for to obtain a solid piece. Hold on the fire is off for to retire it for to don't break nothing.

It's very suitable if you haven't experience with the clay you search more information for to operate and do 2 o 3 pieces at time because always there is a one piece fails if you aren't a expert in the matter.

Examples of cooling fins.

Flywheel.

The flywheel is a object very funny and you can make it with clay using a can like a mould. Nevertheless is more fast and more durable if you make it with concrete. For this ocassion use two cans like moulds, a can more bigger than the other one, find the center and drill it both. It's convenient to cover both with paper for to avoid the concrete glues to the cans. That is it all and be patient for to retire the piece at the 2 o 3th day. The small cylinder with the hole for the axis you can build apart with concrete too, using the neck of plastic of a botle of 1,5 litres. Make it the hole for the crank both pieces before to glue with cement. 

The final piece in concrete and an alternative in clay.

Ball bearing box.

Añadir leyenda

The ball bearing box is a small piece that contain the bearings for your machine. Usually you may have 2, made in clay with only the help of a table, a roller, a knife and something for to make the holes for screws. Don't worry if the piece is not perfect because you can file after and have a good finish like this. If the money is not a trouble you could make it in epoxy and the result could be great.



Pistons

One idea for to make the power piston is with clay, for that we can use a mould like a length of hose and after we give the final form with a knife.




For the displacer is better to use concrete very fine because the clay could be problematic with the cracks during the fire for to have in the center a axis of iron.


Small pieces.

For the small piece we use the metal for example, the crankshaft, the con-rods, the crankpins,etc.






 

Cylinder.
For the cylinder in our case we used a cylinder made of clay with a candle like mould and covered with a grid of iron and refractory cement. The result was wrong, for that we have thought that is a good option for to experiment the glass, for example: test tube.

Some pre-maded items.

 -Buiding our engine can be difficult because there isn't literature specialized and the accurate working in home is very compromised. Some items  can be helpful for to get our goal more fastly.

-A test tube, very useful, is easy to find in specialized stores for laboratoies in any city or by internet, generally it resists the heat, there are several sizes and it wall is thin.










-A cup of coffee is ideal if you wish to create a LTD ceramic engine. Make a correct and smoth cylinder always is difficult, a cup of coffee usually is from clay and is glazered.Other good idea would be a clay pot for  plants joined with a tile could be part of a big engine.









-The Pomez stone, used by the women for the skin; it's a popular item in our homes from thousand years. It sells in drugstores. It's light and easy of to model.A good displacer for a typical homemade engine don't weight more than 20 grms. For a displacer in our machine is great too due to have a regenerative effect for its big surface.

-The classical tile for floors is made from clay and is very strong. A good alternative for to make the frame of our engine but you must have a grinder and the specialized tools for to cut and drill it.




-The power piston is maybe one the most difficult mishap in our engine, the piston must be light ( no more 20 grms), offers a good sealing and move freely. A good solution for this could be to use a test tube some smaller than our cylinder and set it two rings of clay, concrete. Perhaps it's better to use the child's clay that doesn't need fire. All is material of to research.


-A dipstick made of crystal, be sell in stores that provide material for laboratories. It's very suitable for rods and if you have tools for to fund the glass you can do miracles.

-Screw, nuts, washers, it's better to use it and don't try to make it because is very difficult, an alternative would be to use another type of union.



And this is all the tested for the moment, now I'm working in a beta engine homemade very similar to this model.


Typical items you can make with clay.

 
As we said before, the clay is a heavy material. The chance of to create a model that works is difficult but we can take advantage of the small pieces for to intend to do something. Small means more easy of to model, to fire,light, strong and cheap There are several examples to look:

 In the left we can see a cylinder of 150 mm lengh and 22 mm of diam; the wall has 2 mm of thick.Be made with a candle  like mold and retireing after it for to avoid craks due to the shrink, we release its interior surface is smooth for our purposes. In the centre there are two cylinder of 70 mm of lenght and ten of diam, like mold we used a width ballpen. We think these item are useful to experiment for a beta engine. In the another hand we have in the right a double cylinder for a gamma engine, made it with the same ballpen.

 A simple cooling with two rings can be made easily and very accurate for our small cylinders. The most important is that the cylinder fit exactly indoor of this piece.

 Working with tiny pieces the precision of to make a piece increase enormously and you can feel you are an artist. In the right you can see two displacer for our cylinders finished. They are strong and light, (less of 1 gram).They are suitable for to join a rod with epoxi and obtain a good mobile regenerator. The clay doesn't transmitt the heat very well and this is an advantage for us.





Second Try.

My second try was a version of the SFA in ceramic, I add a video where you can see the main pieces and how I made them. At the end of it you can see the machine try to move, however the perfomance is very low.You can comment your own conclusions. You can think that I waste my time, of course, but I have learned something and hope that nobody commit the same errors that me.

continue in the page 2.