Stirlingengineforum.com

First off... I am new here, so let me thank everyone for all the great info I have read in these posts, and for any advice in the future.

My goal is to build a power producing engine, even if it is only a couple watts. I have an idea in mind to eliminate some of the nagging issues, like properly sealing pistons, Keeping the maximum practicle distance between the hot, and cold sides, reduce heat migration through the engine/framework itself, and also to keep the flywheel, and generator as far removed from the heat as possible. My heat sources will be the heat from my chimney, directly on my wood stove, or possibly solar in the summer.

Esentialy what I would like to is have two cylinders in line with one another, with one being hot, and obviously the other cool. What I want to do is enclose both cylinders with only a sealed shaft leaving each cylinder. Then to conect the cylinders in two locations for each cylinder so the there are two power stroke per revoltion with the pistons exerting force in one direction, or the other depending on the location of the piston inside the sealed cylinder. I am not sure how to describe it exactly so I have a two simple diagrams that will hopefully make more sense.

This one is a rough view of what my vision is.....



I made a mistake in the drawings by only giving a 45, and not a 90 degree phase on the crank. Hopefully this is something this can be overlooked in order to get the idea because I am not cad master, and this took me too long to redraw until I feel more comfortable with the design. At any rate, I hope you can see the following couple modifications to reach my goals. The first being the orientation to separate the hot from the cold by placing them inline, and using two different connecting points on the crank to keep one piston 90 degrees from the other. Sealing the cylinder with only one shaft for each so that is the only potential area for air to escape, and keeping the pressure on either side of the piston a little more equalized to minimize blow by on the piston. The sealed cylinder should also keep the piston, and cylinder walls relatively warmer by eliminating the ambient temp air from contacting the back of the hot side piston, and also the exposed cylinder walls as the piston would traditionaly be at the TDC location. And of course the most obvious which is extracting twice the energy for roughly half the space, and weight.

Here is another picture with a phase by phase progression from top to bottom. Again the piston are drawn 45 degrees apart, but should be 90. Another missleading thing about the picture is that the cylinders are shown as the same volume, but I realize the hot side should be about 150% of the cool side. Also, the black lines are supposed to be arrows, but are hard to make out in this view.


I think this may work, and my two basic questions are... What diameter should the connecting tube be in relation to the piston bore? Also, when the piston is at the end of its stroke shold there still be a small volume of air, or is it best to evacuate as much as possible?

Thanks in advance for any advice, and I hope to hear from some of you who can help.

Ok, ten views, and no reply. Is that because this idea is complete crap, or is there just no opinions? If this is a crazy design I will accept someone telling me without having my feelings hurt... I have crazy ideas all the time.

Hey, maybe the pics are just difficult, I'm new here too hope it is a welcoming group but it is a holiday weekend too. :o) I'll pull my diagrams though as no comments on posts like this make me weary.
S
-the scotch yoke is a precision job to work right, many creat huge friction with slight errors in geometry. I have made yoke styl cranks with bearing running on inside double-d and that worked to remove micro sticking. I model 1:220 mechanical parts part time.

Stevedigiboy wrote:Hey, maybe the pics are just difficult, I'm new here too hope it is a welcoming group but it is a holiday weekend too. :o) I'll pull my diagrams though as no comments on posts like this make me weary.
S
-the scotch yoke is a precision job to work right, many creat huge friction with slight errors in geometry. I have made yoke styl cranks with bearing running on inside double-d and that worked to remove micro sticking. I model 1:220 mechanical parts part time.

Your probably right about the pics... They make sense to me because I have had the idea in my head, but they are pretty vague.

The scotch yoke was one of my less thought out aspects, but I can see the possibilties, and drawbacks if done wrong.

I think I may be to the point that I just have to start building to get a grip on all of this.

Thanks for the reply!

Umm... well to say at very least, I'm a little confused...
Are you planning to use double-acting pistons? and If so, Why are you connecting the hot cylinders to cold cylinders of the same piston pair? I suggest It wouldn't work because of the cycles would be reversed, and partially cancel each other. There are similar designs with chained 4 double acting cylinders with 90 deg timing intervals.