Edge's 6 stroke Beta Stirling Engine


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  • Time for something new. I wanted to create a combustion engine and especially the (old) air plane star engines are looking amazing. Before going there, I like to create a stirling engine first. At least this looks more easy to do..

    Some nice info could be found here:

  • Defently worth reading: Stirling Engines: a beginners guide
    Very nice information about Stirling engines, by:
  • Koichi Hirata
  • Jan Ridders
  • And have a look a different animated engines: animatedengines.com
    So after reading the complete world wide web about this subject, I think I'm ready for it.

    The plan:

  • Stirling Beta type: compact, but complicated due the 2 pistons in one cylinder
  • Add linkage system, for right displacement (phase shift)
  • Piston config: star (I haven't seen this one yet...) :)
  • Nr of pistons: 6 (Cylinder bore: 16 [mm])
  • Heating: tealight (6x).

  • Let's start with a CAD drawing, to figure out a nice configuration about size & motion of the linkage.

    That's looking fine. None of the linkages collide, except the blue excenter disc. But that's simple to solve.

    Before creating 6 cylinders and figure out it's not working, I'll build just one Stirling engine first, based on the same dimension like to 6 piston version:

    Starting with the cooling element & some plastic parts. Now I got some feeling about the real size.

    Add all levers & mount everything together. Surprisily it runs very smooth (like it should)!

    I ordered some glass tubes for the displacer cylinder & piston from InstruLabo. This will be the hot side of the engine, instead of the stainless steel. So also the design will be changed a little. Let's wait for the package to arrive...

    The glass testing tubes arrived after 2 days. So now it's time to shorten those tubes. Actually that was quite easy. Just put them in the lath, turn very slowly (~200 rpm) and just cut them with a dremel cutting disc. I also used some oil for cooling. With a little patience, both displacer cylinder & piston are cutted very easy.

    Since the design is changed, time for an update:

    Today a good day, all the parts for the displacer are finished. Also started with the power piston, this part is of stainless steel, gliding over a brass shaft. I hope the tolerances are small enough.

    Also the work piston is installed and the connection of the brass piston rod. When now turning the engine around by hand, it will not even make 2 complete rounds by itself. There is way too much friction in the system. I did underestimated the importancy of friction. So it makes no sence to fire it up.

    Since the beta stirling had a lot of friction, I started again with a more 'simple' gamma type approach:

    Currently this engine is also not working. Some learnings:
  • While running without heating, the flywheel stops very quick, mostly at the same position. Could be caused by not having exact 90 degrees phase shift.
  • I based this design on the work of Koichi Hirata: Model LSE-10, but did not have the smaller piston diameters he used. So propably the fly wheel will have to low inertia.
  • Also the displacer is not fully using the area of the hot piston, I don't know how important this will be.

    After heating up the tea-light:
  • The glass piston reaches about 225 [deg].
  • It's clear the engine wants to rotate, so it to makes some turns, but slows down agian.

    Despite the effort, it's just not working. I want to create a new fly wheel, with correct phase shift & higher inertia. Hopefully this will solve all the issue's...