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Hello, with the help of a friend who has a 'shop' I'm building a
displacer type Stirling engine of let's say medium size. The
displacer cylinder will be 24cm long and 8cm wide,
how much of the space (%)should be occupied by the displacer?

The working cylinder will be 4cm wide and will have a 4cm stroke,
hope this is ok?

Thanks for your advice?

Igor

Hopefully you will have enough power to run the engine itself. If you want to ensure that it will produce some useful power output you will have to acquire a lot of technical expertise to accomplish that purpose. Designing a Stirling engine with power output is no simple matter to be undertaken lightly.

So, what you are telling me is that all this Stirling talk is just a waste of time? They are useless...
Maybe this should be stated more clearly on this site...

Did you ever try to build one? And what were the problems you ran into?

Thank you for your input.

Igor

What I am telling you is that there is far more to building a successful power producing Stirling engine than the ratios or dimensions of the cylinders. It requires an understanding of the underlying Physics and Engineering topics applicable to the design and fabrication of the machine. These include but not limited to thermodynamics, heat transfer, fluid flow, mechanics, properties of materials, etc. Visit the web site NotSCar.wik.is and look for links to the engineering courses offered by Ohio State, and Penn State universities for an overview of the courses on Stirling engines offered to their 3rd and 4rh year students.

Building a LTD, Low Temperature Difference, model Stirling engine is no problem as there are many designs, and photographs available on the internet if you take the time to look for them. Made from empty food cans to finely machined works of the machinist's art.

It is not so much the dimensions you requested as the expertise in design that you need.

The swept volume needs to be 1.5 to 2 times the swept volume of the power piston. It shouldn't take a rocket scientist to figure that a lot of power requires a lot of heat. There is no free lunch. Its the materials and quality of workmanship that determines a good engine from a bad one. For example to build a LTD one doesn't need to spend $500 to get an engine that will run, when you can build one from parts in the kitchen cabinet. I would love to know what the materials cost them to make one of these. Of course, if you want some serious power you need a power piston the size of a coffee can.