Lamina flow stirling engine

[PalmRunner]

Hello everybody.

Check out my websites, could be of interest to some of you:

http://picasaweb.google.com/PalmRunner
http://www.youtube.com/watch?v=cjjkj-UGboM

Lamina engine is wrongly reffered to a thermoacoustic device, but in any case it is the most simple power producing engine.

[Administrator]

Excellent engine.

The Lamina is my next engine to make. I have three different plans for it right now. I like the way you secure the test tube to the engine. That is a great idea! Nice mounting of parts also! Very nice!

There apears to be 2 or 3 different versions on your links. Same engine different flywheels?

DB

[PalmRunner]

Thanks boydhouse,
You noticed correctly, only the flywheel is different. At first, I was not happy with the quality and how it looks like. The flywheel was made of pottery compound cast in the bottom of a Cola bottle. I changed the color, but was not happy again and finally came to the idea for using a bearing as e flywheel. It has more natural view; it is quite accurate and can easily be balanced, which is important at speeds of around 1000rpm. You may already guess that I don’t have a lathe , so you can imagine that producing nicely looking and accurate flywheel may become quite a big issue.

[Joan]

I just started making my own LTD engine, my next challenge is a lamina flow. I have seen yours, it looks feasible for my workshop (no lathe as many of us). I have a test tube and an Airpot sample similar to what I see in your's engine pictures.

Could you please share with me a plan of your engine with dimensions? That would be very helpful together with the pictures.

Many thanks in advance

Joan.

[PalmRunner]

Hi Joan,

A haven’t used any specific plans. The engine is very simple and the pictures are self explanatory. Everything depends on the available materials. Nevertheless, there are few things that have to be considered:

1. The Airpot set comes with a very convenient mounting stud that I used to screw the cylinder to the aluminum stand. The problem is that the bore in this stud is very small ~2mm. You should carefully drill this opening up to 5.5-6mm to avoid losses at higher speeds.
2. Airpot cylinder is way too long for a piston stroke of 30mm that I use in my engine. If you don’t want to cut the cylinder you have to use relatively long piston rod. I preferred to have more compact engine and cut the glass cylinder to what is needed for a 30mm stroke. Since I don’t have special tools for cutting glass, I used a basic Dremel tool and the diamond disc that comes with the kit.
3. The test tube volume is fairly important, because it determines the compression ratio. It should work with almost any size, but reducing the test tube volume increases the compression ratio and the engine power/speed. In the original configuration I used 155/15 mm test tube and the engine speed was ~ 1000rpm. Later I reduced the test tube volume twice, by putting a rubber tap inside the tube. Now, the top speed of the engine is almost 1700rpm!
One problem with reducing the tube length is that you also have to shift the heat source closer to the cold area (the piston side) and it gets hot faster, reducing the engine speed down to 1400 - 1500 rpm after several minutes. To overcome this, one can use longer, but narrower tube, keeping in this way the volume constant and the heat source away from the cold area.
4. Using a metal tube may improve the efficiency, because of its better heat conductivity.

Regards,

[Dom]

Hi Palm runner,

Awesome looking unit there, and considering no lathe used, wow what an acheivement.

The last couple of days i've been going crazy, I can't seem to get mine running, ive re read some docos, and really scratching my head what to do next, ill upload some photos to you if you like, of what i made, but they have changed along the way, because i couldnt get it to run.

I noticed that you bolted a backplate to the neck of the test tube, my one has no outer lip on the end of the tube, maybe i should get a test tube that has an outer lip, Another question like to ask, should you feel some bounce happening, because i'm not getting any bounce at all, there's compression, but the alum pipe does have a slight gap inbetween it and the piston, even so, when i test the alum tube, put it in my hand the piston moves down slowly. hehehehee sorry for all of this, just would love to get it working.

The graphite piston, how did you go about making this?, ive got long rods, that i cut first, then drill and clamp a handle to the piston, then i use sandpaper and shave of by hand, as im turning the tool.

Could you also tell me how you cut the end glass tube, where the graphite piston sits, I know you said dremel tool, i looked this up, just wandered if you held the tool in hand and put the tube in a vice or something, i'd love to do this with the tube i got , as its 180mm long, therefore i can still use this tube as well. Right now im using aluminium tube for the piston cylinder.

The airport, that your using, where can you buy that?

by the way thanks for the tips,

kind Regards,

Dom

[PalmRunner]

Hi Dom,
Please upload some pictures of your engine to get better impression about the construction and the dimensions. There are several reasons that prevent the engine to run. First, as you probably know the friction is a big enemy. Try to minimize all possible frictions. I am not sure how graphite piston works with aluminum cylinder - never tried. Your method for sizing the piston seems to me good. As a final step you should use ordinary paper instead of sandpaper. You should also polish the cylinder walls perfectly. Do graphite and aluminum have similar temperature expansion coefficients? Try to use graphite piston in glass cylinder - works perfect.
About cutting the glass cylinder. I fix the dremel tool in a vice and let it run. Hold the glass cylinder with both hands and very carefully and slowly approach the diamond disc, rotating the glass cylinder at the same time. After 2-3 rotations the scratch is deep enough and the cylinder will break in this place. Then you can varnish the roughs with a standards cutting disc.
The airpot piston-cylinder set I got as a free sample from the company.

There is one detail in the construction that maybe you miss and could be a reason why your engine does not work. I have this detail only by chance - it is the mounting stud of the airpot set. It forms kind of a baffle, or restriction between the working cylinder (the cold area) and the hot chamber. Several Lamina builders reported that without this restrictor Lamina runs poorly or would not run at all. The exact function and the optimum size of this baffle are not yet known to me.
Here is a picture how this restrictor should look like:
http://www.kontax.co.uk/docs/thermohowitworks.pdf

PS. Don’t believe to the explanation given in this pdf. The engine has nothing to do with thermoacoustics.


Regards

[fishsmoker]

Hi,

I do not get a piston fabricated with my little lathe that is airtight enough and has not too much friction to make a lamina flow. indeed i cannot even push the aluminum piston out of the glas test tube or a hydraulic steel pipe (probably too much leakage) even a millimeter. even though i heated the test tube with a torch. did you know that you can melt glas with a soldering torch...?

I read that some of you use fabricated low friction graphit pistons.

Has someone tried a lamina flow engine with a balloon instead of a piston. at least this is airtight and has no friction.

since i work on that lamina i now and then have to convince myself that it is possible at all to run an engine on hot air by watching my little candy can stirling... :-?


someone can help or has even tried the ballon.lamina?

[daniel_bingamon]

I've been working on a Lamina Flow.

Didn't quite get this one running. It got so hot that the cap on the end desoldered itself and disappeared in my workshop.
The flywheel has a small bearing in the back, it turns freely and the piston works fine when the cylinder is vented.

Question, does the smaller tube need to have a insulator between the larger tube? I have pieces of brass stock in the center of the small tube to act as the regenerator.

From the previous post, I wonder if I'm having difficulties with it also because there is no restriction between the two tubes.

[G-18397]

I have noticed that you also have another video on youtube called LTD Stirling Engine. Did you follow any specific plans and if you did can you share them with me because I am very interested in building one of them.

Thanks.