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| Brass Stirling (#3) |
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| cidrontmg:
Hi Mad Jack, right you are in that a blind bore can be reamed. Another thing is, if itīs worth while. In this case, itīs a short cylinder, 1.4", and the piston stroke is only +/- 6 mm (1/4"), from the bottom. That means the piston crown would work entirely in the conical area of the reamed bore. I think itīs easier and faster to just bore all the way, if you must bore it anyway for the bottom part. Saves one setup! About the copper/brass connecting tube - Iīve also been seriously considering that. Not only would it be tighter (if done well...), it also would not be flexible, like a plastic tube, which will expand and shrink with pressure variations. I realize it wonīt flex much with the pressures weīre talking about, so itīs more theoretical. And plastic tube does work in practice. But even so, in comparison to a metal tube, it will flex many times more, and weīre talking about very small pressure variations. Any flexing is power lost. Another thing would be the looks. A brass tube wins hands down. I donīt like the looks of plastic tubes in small steam/Stirling engines, they seem cheap, and out of place, and temporary (add any other derogatory adjectives here). The only snag in using a brass tube is, it would probably need two junctions, and it is very short, an L with 10 x 20 mm legs. One alternative would be to soft solder it in place... This needs some more consideration, but Iīm fairly sure that Iīll make a brass tube before even trying it for running. Hi picclock, yes indeed, Teflon and heat/steam donīt mix well. Iīve heard about (never did myself) PTFE pistons in steam engines, and they can be made to work, but itīs not very straightforward. I wouldnīt even bother with a Teflon piston in an I.C. engine. Gamma type Stirlings however are "different" beasts in the sense that the work cylinder/piston never gets hot, usually not even warm (and if it does, thereīs a grave design fault...). In this particular design, the cylinder is quite massive, and bolted to the thinnish base plate. The base plate admittedly also carries the displacer cylinder, which will heat it somewhat. But I fully expect that after even a longish run (1/2 hour), the work cylinder will be only modestly warm. Should that prove not to be the case, I will mount the cylinder to an ali plate. Next step would be this. Otherwise, it goes to a wooden base board. :) Brass is nice to work with, it will polish relatively easily, and stay that way, for a while at least. And it can be blackened also easily, I am considering blackening the displacer cylinder. It would also slightly help with cooling, but of course it would be more for the looks. And maybe also blacken the screws. Here (almost) properly aligned. I guess I will blacken a few, see how they would look. :wave: |
| cidrontmg:
Fat lady sings again. A picture of her with many swinging arms. I also did a video, technically awful, shaky hands and poor eyesight. But the essential is there :med: She needs quite a bit of pre-warming, but then runs and runs. One lamp fill of spirits will keep her happy for some 40 minutes. These machines seem to need longish run-in periods, they pick up more speed the longer you run them. Common to many other engines. But she runs quite happily as it is. Iīll post a few more pictures after itīs blinged and cleaned a bit. For now, a clunky Stirling for Christmas bells :lol: It is mounted to a piece of Chinese bamboo kitchen cutting board... Thanks for watching, everyone, and a merry Christmas (if you celebrate it). :wave: |
| madjackghengis:
Hi Olli, good to see you get the engine running, it looks good and sounds very good, complete with real engine noise. I had suggested the copper tube because of its smaller volume, and being able to soft solder it in place, "minimizing dead air", but you're right about expansion and its effects on efficiency. I take it you don't have to revert to a heat sink and can use the wood base you'd planned. All in all, a fine engine, and I think I will have to emulate this one. I found a smallish cigar tube in my tool box, it's been there for a couple of decades, but I just found a piece of very thin walled stainless tube which is the right size to go with the cigar tube, and I like the style of your engine, so I think I will be making a similar one soon. Very nice all around, and a nice looking and sounding video as well. Merry Christmas, and God Bless you in the Coming New Year. May God Bless us one and all. mad jack |
| Stilldrillin:
Olli. Yer've done it again! :thumbup: You're making it look very easy now! :clap: :clap: :bow: Wishing a Merry Christmas to you, and all MadModders, everywhere..... David D |
| NickG:
Really nice Olli, well done once again! :bow: |
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