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| Wrestling with Robbo........ |
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| Stilldrillin:
The original posting of this year's initial rebuilds, got a little lost, among the offers of auction lots. So, I've reconstituted the Robbo postings......... Time to start on Robbo...... You've all seen the story, up to pres.......... http://madmodder.net/index.php?topic=6110.0 First off. I don't like relatively thick wall, brass hot caps........ Too much heat can pass to the cool end. So, I sawed it off, to replace with a piece of steel vacuum cleaner pipe...... I noticed the original end cap was concave copper, and painted black, to absorb the heat. A rub with emery highlighted the hammer marks........ I radiused a piece of delrin, and gave it a tap, or two........ Looks good now........ Carefully parted off, just behind the cap........ Bored the cool end 1/8" deep to take the chrome pipe, and cap. Looks ok, I think......... I emeried away the chrome, and silver soldered the cylinder in place........ Then after a clean up, replaced the original copper cap...... Another clean, and a quick assemble. I think they look made for each other...... Not a bad day's work....... Need to sort out how to make a lightweight displacer now, cos I don't like the wasted volume of the regenerator. It's nice to be back to it again! :D David D |
| Stilldrillin:
Having now had the time to examine what I'd achieved with the hot cap. I was feeling very pleased with meself. :D I had only ever silver soldered two small joints before. It just goes to show, if enough notice is taken of techniques shown on here, the beginner can produce some very satisfactory work. :thumbup: Displacer time! The cap bore is 1.4". I cut some steel sheet .020" thick, and wrapped it around a 32mm ali bar. Ground the inner overlap to a feather edge, and strapped it tight. Then turned the outer feather edge. Moving the pipe clip section by section....... Swapped the clip for some stout wire, and fluxed........ Then silver soldered........ Just a nice line showing in the bore........ Cleaned up nicely......... I think that will do nicely........ A busy few days ahead, including Harrogate. End caps next. As, and when....... Thanks for watching! :) David D |
| DaveH:
David, Well that has turned out very nice :bow: Great job :thumbup: :clap: :beer: DaveH |
| Stilldrillin:
Thanks Dave. My first proper session of metal forming, and silver soldering, went very well....... :D David D |
| Stilldrillin:
Time for the displacer end caps. I used the original piece of delrin to dish a piece of steel sheet. Then used it with a piece of emery cloth, as friction drive to turn to a sliding fit in the displacer tube..... And silver soldered it into place........ Quick clean up......... I turned an ali top cap. A push fit x 10mm thick. Just for those who love to see swarf......... I milled away some of the weight. Leaving a bridge, for an M3 grubscrew, to lock onto the screwed shaft...... The original displacer shaft bush was made of two opposing gland nuts, with an O ring in between. Didn't like that idea. Locktited the glands in place. Drilled out and re bushed at 4mm dia. Then milled away the hex head under the deck, for even less dead space......... Next job was to temporarily re-assemble and give it a try. Dunno why the little end is so noisy....... Hmmmm........ :bang: Time for another think, I think. David D |
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