Stirlingengineforum.com

I have been experimenting with the walking beam engine with my nephew and along the way I have had a few ideas hit me that I wanted to run past the forum for feedback/input.

It occured to me that maybe if a spring is added to the bottom of the displacer piston, the recoil or spring energy upon landing on down cycle would transfer and assist in rebounding for upward cycle.

Thoughts...... ????


Also pondering if using a beer can as an "alternate" type of displacer piston would be feasible?
I believe the crown that is stamped inversely on bottom of can could be strong enough to J.B. weld a small nut to and be able to take the force.
( using bottom turned upward and making as top of piston )


Thirdly..... I am having difficulty locating something/anything to use as a seal / piston ring or separator to divide top from bottom of cylinder around mid-point of displacer piston.
The displacer housing has an internal diameter of 2 and 7/8 inches and the outer diamteter of displacer piston is 2 and 3/4 inches.
I had thought of using an over-sized VITON o-ring but alas, they make no such size as I have seen.
Any ideas ???

McGyver,
Sping assist has been talked of before and I think the energy required to compress it out weighs the benefit it provides on up stroke. If your displacer is balanced with weight on the flywheel you will have better results. Ideally you should be able to stop the engine in any position and it will stay without the displacer or power piston pulling the engine around to bottom.

I think a aluminum can for the displacer should work but don't know if others have tried it successfully.

Lastly, you don't want to seal the top from the bottom in your displacer cylinder. The air needs to freely flow from hot to cold for the Stirling cycle to work. You don't want an excessive gap but at the same time, you don't want the displacer compressing the air as it moves either. Any compression in your engine should be created by the power piston/cylinder only.

I hope that helps.

Thanks for the feedback, Cartech, I appreciate that.

So what if I drilled a couple holes on the sides of piston seal to open up just a few places for air to move about ?

At least this way I could add more airflow until I reach the required minimum or therabouts ????

Also was thinking if I used a really super light spring.... talking featherweight strength it might be ok .....but thats questionable as you say.

Can you remove the seal rather than make holes in it? I'm hoping there is no contact with the displacer or the friction will prevent your engine from running.

I still think the spring isn't needed if the engine is properly balanced and it will likely add unwanted friction to your engine. The displacer needs to reach the end of it's stroke in both directions but not quite touch. Even a light touch can cause too much friction from the very small amount of binding it will cause.

As cartech said.

I don't think you want the displacer airway to be constricted down to a couple port holes.

I would think that the air should move freely around the entire diameter of the piston and get as even a temp distribution as is possible.

You can try a spring but I think the flywheel has way more effct than a spring could have.

see ya
good luck