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Hi DavePeople get quite confused by the alpha, beta and gamma configurations of Stirling engines. I am not sure if the terminology is very helpful but I suppose using Greek letters adds an air of academic respectability. The gamma configuration has separate power cylinder and displacer chamber that are linked by a tube. This configuration gives a lot of flexibility for the linkage so for example the power cylinder and the displacer chamber can be at 90 degrees to one another and both work from a single crank pin (As the Stirling 90 described by Anthony Mount in Historic Engines worth Modelling Vol 1) or the two chambers can be parallel to one another and the linkage uses two crank pins 90 degrees apart (Typical of Heinrici HA) or by the use of a bell crank linkage (as used by T E Haynes in his engine described in Model Engineering for Schools Book 2 Incidentally this engine has been described by others in the model engineering world but without giving Mr Haynes his due recognition) The downside of the gamma configuration is the dead space due to the air in the transfer pipe and possible restriction of the pressure pulse between the displacer chamber where it is generated and the power cylinder. The beta configuration has the power cylinder coaxial with the displacer chamber and in the best designs the stroke of the power piston overlaps with the swept volume of the displacer. There are lots of engines that work like this such as the Rider Ericsson pumping engine and the Heinrici HL type. From my observations at Stirling rallies and exhibition stands beta engines outperform gamma engines and I have always attributed this to the reduction in dead volume and the free flow of air between the working cylinder in the displacer chamber.The enigma is the alpha engine. These should be the best engines in terms of specific power output and the ones that have been well documented do indeed run very well and produce a lot of power for their size. That being the case why in over 10 years of exhibiting Stirling engines at model engineering shows and rallies have I only ever seen one alpha engine running? The alpha has two pistons set 90 degrees apart and the cylinders are connected by a transfer pipe that often incorporates a regenerator. In full size the Haywood Tyler engine is an example of an alpha engine. I suspect some Haywood Tyler models are actually gamma configuration engines rather than true alpha engines.Rather contentiously, is an alpha engine just a gamma engine with a big fat displacer rod the same diameter as the bore of the displacer chamber??Bob
Your set of castings is Andy's interpretation of the E T Westbury design. On the square water jacket you might notice a rather steep angle of draught around each water outlet? This was done to make the " draw " from the sand mould easier to accomplish.
It is full sized: it has a 30mm bore same as the original Heinrici engine. Jo