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| Wrestling with Robbo........ |
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| Stilldrillin:
Well..... I've done all I can to improve the existing parts. It is so close to running! And very much improved, over the lifeless lump I first tried. I've had a good think, and a measure round........ I read, somewhere, the displacer volume needs to be around 1.6 times, (or more), the power piston volume. The displacer measures 1.32" dia x .45" stroke. The power piston measures 1.018" dia x .73" stroke. Giving a ratio of only 1.037.... Hmmm.... If I reduce the power piston dia. to .8"...... This will give a ratio of 1.68....... If my sums are correct. Anyone got a comment? Or two pennorth? David D |
| sbwhart:
Just checked the calc through using my long winded way and I get .796 so .8 is the man to go. :D :D Stew |
| OldMetaller:
Nice work David! I could see some Old Machinist's tricks being wheeled out there! I especially like the Delrin dodge! Regards, John. |
| Stilldrillin:
Thanks for your comments Chaps! I found the advised ratio is 1.5....... So, I made the steel cylinder with a bore, around .843". Stuck it into the original cylinder, using high temp slide lock. Then honed it, using a piece of delrin, and fine grinding paste........ All done....... Turned the piston to +10 thou' , and parted off....... Screwed onto an M5 threaded mandrel, and finish turned. Removing the last thou' or so with fine emery, backed by a 6" rule, a la Cedge......... Looks ok, I think......... Lit the burner...... So sorry for the amateur dramatics! But....... You know how it is.......... It's been a good day! :D :) :D :) David D |
| Rob.Wilson:
:clap: :clap: :clap: :clap: :clap: She goes like the clappers David :clap: :clap: :clap: :clap: I always fined your "bring em back to life" threads a great read ,,,,,,,,,,, well done :thumbup: Rob |
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