My first stirling engine (LTD gamma DIY project)

[Soeren]

hello,

I just wanted to show you my first stirling engine. It is a (nearly) LTD gamma engine and I made it as a completely DIY project (without all the expensive tools i.e. a lathe).

All I used was a drill, a saw, a razor blade, a Scissor and a lot of glue. This is the list of materials:
* 3 lids of gherkin glasses
* some drinking straws
* a copper wire (1,5mm)
* some nails (1.4mm) and some small srews
* a wall plug
* 2 old rulers
* some wood
* a piece of polystyrene and some balsa wood for the displacer
* a piece cut out of a PET bottle for wall of the displacer cylinder
* some adhesive tape
* some rubber of a balloon
* a screw cap

Well, it is not really a LTD stirling, it needs nearly boiling water on one side and some ice cube on the other side, but at least it runs. Just check the videos

a short one:
http://home.arcor.de/soeren_scharf/Pics/RMOV2934.AVI (1,72MB)
and a longer one:
http://www.youtube.com/watch?v=enHiUnLoaPo (0:51)

currently I am removing the tape from the displacer cylinder, it was there provisorily to see if the engine is running at all. Now I can glue the bottom lid and then the displacer will be visible too.

regards
Soeren

Edit: moved the longer video to youtube due to limited traffic on my webspace.

[Soeren]

hello,

Now I have finished my first stirling engine. This version got a new and more precise displacer and a new wall for the displacer chamber made of a 1Ltr Sprite bottle. The gap between the displacer and the wall is 1mm.

The required temperature difference is much lower than in the first video. Cooling the top lid is no longer necessary but still helps a lot. Also on the hot side the water does not need to be boiling.

It seems that I have to take care of the clicking noise, when the air pressure bends the lid, because it seems to cost too much energy. I glued two nails on the bottom lid to make it more stable and now it runs much smoother. Only with high temperature differences there is still a noise.

The fastest speed that I could observe was 150 rpm with boiling water and some pieces of ice cubes on the top.

I am happy now with the result and think about building the next machine, maybe a sun powered stirling.

And of course I have made a new video: http://www.youtube.com/watch?v=L1JoJFai40c

regards
Soeren

[Soeren]

...
I notice you have a wooden bearing/crank support structure on this engine. How did you affix the cool side plate and this wood?...

I just glued it, with the low forces by this machine some glue is sufficient. In the first step I tried to use some screws but using screws would bend the lid because the lids are not completey flat usually.
This construction with the wood parts has a big disadvantage, it takes about 18cm² of the area of the top lid, that is now thermally isolated, so the top lid has not enough cooling area. So for good results some extra cooling is needed (cold water or ice), without this it only runs for some minutes.
Now I am thinking about a more simple and more efficient structure for this part.

...
Plexiglass can be very easily formed when heated. Do you feel that a strip, formed
around a mold, would make a good displacer chamber? I realize the ends
would need to be welded/glued/joined but good agents/chemicals exists
to do this.
...

The intention was to build a LTD engine so there is no temperature issue with plexiglass or any other plastic material. But even with boiling water there won't be an issue, just test with an empty bottle of coca cola, fanta or sprite and fill with boiling water, it won't deform.
My original goal was to construct an engine that is possible to be build even by a child by asking its mom for some waste parts out of the kitchen. This is the reason why I have chosen bottles, lids and so on, and construced a LTD engine (who wants to see his child play with fire to power a stirling?).
The third reason to use a bottle is that I wanted to make the displacer chamber transparent. On http://www.instructables.com I have seen a machine where the top of a CD case (cakebox? spindle?) was used, this gives a bigger displacer chamber than using a bottle.

regards
Soeren

[Administrator]

test...sorry