My father had one of the Solar Engines Stirling engine models as well as Andy Ross’s book on Stirling Cycle Engines. The engine is currently in my brother’s collection in England so I thought I would try and build my own version.
There have been plenty of fine models on here but most are too large for my machines and being me I wanted to design my own. There were a number of initial considerations:
-An open engine where all the linkage is visible or a closed and pressurised engine as a (limited) power producer?
-A coaxial cylinder rhombic drive or two cylinder with twin crank or a Ross Yoke drive?
-I discounted a 4-cylinder Rina type as too complicated for the first attempt.
I decided on a rhombic drive where I could leave the crankcase open or seal it up to try a pressurised system. Some internet searching came up with various useful bits of information. Andy Ross had made a successful 11cc rhombic drive engine. Dr Senft has built a 5cc version and there are some plans for an open rhombic drive engine from Jan De Waal which is in the same size range. I also came across some design calculations for rhombic drives on the StirlingSouth website.
Looking at sizes I have laps for a 25mm bore, MOD 1 30 tooth gears and a 7.5mm crank throw will fit in a crankcase I can machine. Without doing accurate calculations that will give a swept volume around 8cc.
For materials I am thinking of stainless steel for the cylinder and displacer with a cast iron working piston. I will use tube if I can find suitable sizes otherwise they will be turned from solid.
I started laying out the rhombic drive using the ratios suggested by Dr Senft to see if it would all fit together. It looks possible although the crosshead for the working piston is a little tight if I use ball races. The start of the layout is attached.
Any thoughts? Have I missed something vital?
