Alpha type engine, is it going to work?What for regenerator?

[masterbc]

Hi everybody!
I want to build alpha type Stirling's engine, I have two the same very hermetic cylinders with pistons from car engine and something, let's call it project with description (it's attached).

Is it going to work? I was thinking about construction like in a two-pan balance.

What would be the best for the regenerator? Is it necessary? One guy told me that car heater would do but really I'm not sure about it.

Thank you for advice and discussion.

All the best,
masterbc

[Ian S C]

Masterbc, Instead of the beam arrangement, perhaps look at Andt Ross's Ross Yoke.For the regenerator, many sheets of stainless steel foil/ shim, or stainless gauze (very fine), or coils of fine stainless wire. I don't know where your mate got the idea of a car heater! In the early days of the Whispergen designed here in Christchurch NZ automotive catalytic converters were tried, without much success. Because of the fuel grade at the time, the converters were removed from cars imported into NZ.
You won't be able to directly transplant automotive pistons and rings, you may be able to use the piston on the cold side with low friction rings, but on the hot side you would be better with cast iron. As the con rod has a vertually straight action, the piston only requires a very short skirt. The hot piston should have a cap on it, this is called a Heylandt Crown, this moves within the hot cap of the motor, and the concentric regenerator can be built into the hot cap. Properly built a motor this size, even unpressurized should be quite powerful. Ian S C

[masterbc]

Thank you for advice.
I understand that hot and cold gas shouldn't mix, yes? So the pipe isn't needed. What about using many uninsulated copper wires? Or many wires insulated together? Copper would be good, because is great heat conductor, what do you think?

I was considering using polytetrafluoroethylene in cold cylinder as it slippy and can't stand heat, but there it would be fine I think.

masterbc

[Ian S C]

You do not want copper wire, it conducts the heat from the hot end to the cold end too fast, thats why stainless steel is recomended, in the early days of hot air engines wrought iron wire was used for the same reason.
There is a Teflon/ PTFE resin paint that can be baked on, and would be OK on an aluminium piston in the cold end, but a plain cast iron piston in a steel cylinder should be used in the hot cylinder.
I was just wondering how many motors have you got going, you need to get a simple one running well, before you start designing a complex one that might be difficult to get going.
As well as building you must read up all you can, make use of the library, second hand book shops etc.
Do you have a lathe? Also a bit of a workshop. I have enough of a workshop to be able to do most stuff, except welding thin stainless steel, a mate runs a stainless steel fabricating shop, and he TIGs some bits for me, although he does'nt like some of the very thin stuff I get him to do. You need to use all resources, people included. Ian S C

[masterbc]

OK, I understand, conducting shouldn't be too fast.
Actually it would be my first engine and I don't want to screw it up. If this one is working, I'll develep it very quickly, if not- I'll probbably give up working with this project (straw enthusiasm;)).

I was looking for information about alpha type, but only in the internet, I'll try to find sth printed.

I don't have lathe, but it's not a problem, near me are good experts, so I don't have to worry.

In your previous post, what did you mean when you was writting "a very short skirt"?

all the best,
masterbc

[Ian S C]

Masterbc, the skirt of a piston is the side of it, the part that rubs against the cylinder, the top is the crown. Because the con rods on the Ross Yoke type motor run in a vertually straight line compared to those on a motor with a conventional crankshaft, there is not so much side ways pressure on the cylinder wall(less friction), so, as there is less twisting of the piston we can get rid of quite a lot of the skirt of the piston as its not required to keep the piston straight in the bore(again less friction), every bit of friction you can remove the better, and you get rid of a few grams of weight too. As I build my motors, I have a small set of scales to weigh the parts on. First I make the part and weigh it, then look at it to see if there is any metal that could be removed without weakening it too much, some times I go too far, ie., piston skirts, I make pistons from (low grade) cast iron, and thin the skirt to about 1mm, some times a little less, some times when finaly polishing it the skirt has broken off, so its start again, I make the piston fit the cylinder, then I rebore the inside, and if I'm not carefull the outside dia gets distorted.
Ian S C