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When we say an alpha stirling is XYZcc, is that the displacement of ONE cylinder, both cylinders or the maximum engine volume?

I'm not sure, but I would say it's the total of both cylinders. Not much help am I.
Ian S C

Here is the thing. If we are using the displacement to indicate the amount of gas the engine heats up and cools down (this is how IC engines measured), the volume should really be 1.5 * volume of hot cylinder(or cold cylinder).

The displacement of a engine is the volume of the power producing cylinders during one full power stroke. This excludes any other volumes like heat exchangers, or working fluid(air) being supplied to the power cylinder, weather it be by another cylinder or outside source.

Although in the alpha configuration I am not sure if both cylinders is seen as power producing. The whole system is under pressure and there is a part of the cycle where both cylinders move downwards under the expansion of the heated working fluid(air), thus producing power.

Neither of the cylinders in the alpha can be seen as a slave/displacer cylinder. I would vote that the volume of both the cylinders excluding transfer passages and heat exchangers can be seen as the displacement of the engine.

Andre

By that definition and with an ideal stirling cycle, only the hot cylinder is producing power. Here is monkey wrench I am throwing. After the gas is cooled, the pressure in the system might be lower than the environment (depending on snifton valve operation), so some power may or may not be produced during the compression stroke.

Hi... i am new here...
i have built type alpha V-type with ratio displacment 1.5:1... but it doesn't work... in type beta and gamma the ratio is 1.5:1... can i use that ratio in type alpha?

aragusta, the ratio for an ALPHA motor is 1:1.
Both cylinders in an ALPHA motor are power producing. The volume would be an average of the two cylinders, as the total volume changes through out the cycle.
Ian S C

Tq for your help Ian S C...
I already saw video Inside a Stirling Engine Andy Ross Stirling Engine Kit Design ... inside that stirling has a piston and a long piston like displacer piston... is that true long piston is displacer? If not, why piston in the hot side longer than piston in the cold side?
because i have built alpha stirling engine V-type with ratio 1:1.5 but it doesn't work...

The size of the piston has nothing to do with the displacement of the cylinder. If you look at the image of an alpha stirling from a classic text book, you will notice there is no way heat up and cool down the gas. The reason for the long piston is to force the gas to go through a small area with large surface (which acts as heat changers, both hot and cold) so the gas can be heated up and cooled down. Also keep in mind that when pressure changes, it affects the entire system, not any particular cylinder.

Thanks for your advice Aviator168....
first i will make the ratio 1:1.5 into 1:1 with extend the diameter power piston hot side 30mm into 36mm... the diameter piston cold side is 36mm... any advice?

The fitting on the hot piston is called a Heylandt Crown, it does keep the heat away from the fitted part of the piston.
If you haven't got it yet, down load Andy Ross's book "Making Stirling Engines" it's a free one.

Sorry... i still didn't found a Heylandt Crown in Andy Ross's book.. can u explain where is a Heylandt Crown ? Is that at the burning side like a cap? Thanks...

Ooh... i understand where is a Heylandt Crown... is that patch on the heat piston ?
But i have one question in my mind... is that vacuum in the Heylandt crown...? Like this image...i hope anyone give me a advice... thanks for your help...
http://imagizer.imageshack.us/a/img909/7640/nLPhYC.jpg
thanks for your any answer...

The Heylandt Crown is constructed in a similar fashion to a displacer as a thin walled, usually stainless steel cylinder. It is sealed, but a vacuum is not required. If one could form a vacuum (at least partial) this might reduce heat conduction, never thought of that one.
Ian S C

This is another image...
http://imageshack.com/a/img540/559/03LUQU.jpg

thanks for your response Ian S C...
how about the weight of cold piston and heat piston... ?

I make weight of piston Heylandt Crown 165gram and piston cold 45 gram... how heavy piston do you make Ian S C?