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| Scott Vacuum Engine...... |
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| Stilldrillin:
Introducing Scott. Another of my orphan engines. Arrived a couple of years ago. Been patiently waiting in the cupboard. Never run. (I don't think)........ Badly packed, on top of the wad of drawings. Which were penetrated by the crankshaft....... :bang: The shaft was bent, and flywheel distorted. Rather proud of myself, at the time. I made a ballrace nudger. Which got it back, to within a couple of thou'. :thumbup: As it arrived. It was impossible to screw the valve mechanism together, tight enough........ I dimpled the cross shaft, for the grub screw. Then made a temporary return spring........ No joy! The shutter arrangement is much too light n floppy. Had a few pops, only. After I'd caught my finger in the guillotine, for the third time. I decided it was time for some mods....... So...... The engine part is fine. The valve part is 'orrible. I need some info, as to which is the best system to get the flame safely into the cylinder, at the correct time. Some systems are eccentric driven, rather than a cam. I guess that is for quicker open/ close action. But an eccentric will give positive motion, in both directions. I can visualise a push/pull or twisting rod, along the side. How does it turn the corner, to the port? Anyone any ideas? Crap o cad/ pics/ vids, gratefully accepted. David D |
| tom osselton:
Here is one by bogstandard http://www.modelenginemaker.com/index.php?topic=158.0 One site said they made the graphite valve come down so the flame doesn't have to go over it. |
| Stilldrillin:
--- Quote from: tom osselton on October 25, 2014, 06:03:22 PM ---Here is one by bogstandard --- End quote --- Hi Tom. Thanks for the link! :thumbup: That particular valve train, is a very unreliable system. I'm minded to Mod it, the same as my last project. The Bengs, Nick..... Can't be any worse than it is! :palm: David D |
| Stilldrillin:
Progressing. Slowly........ :thumbup: Roughed out a slot, in the c/i base........... Milled a matching slot, and 4 retaining holes, in the hopper........ Matched up, nicely........ It needed a widget...... M3 thread in one end, 3/16" hole in the other, and a 9degree bend in between. Turned the big end, and tapped m3. Held in the rotary table, at 9*, spot faced and drilled 3/16, down to centre....... On to a 3/16" mandrel. Turn small dia........ M3 studding. Turn radius........ Couple of flats. Loctited, to the tubular operating arm........ Bottom of stroke....... Top......... I'm quite pleased, how it's gone together, so far. I've (finally), read up the Poppin plans, and think the lightweight valve is the way to go. Bought some 5thou steel shim. If I can cut it, and keep it flat. I might be in with a chance! The present return spring is much too stiff. I've made a better action, with a small coil spring, under the cam arm. But, I don't want to abandon the leaf spring, just yet. Does anyone know where I can get a sensible length, of 1/4" x .012" spring steel? Thanks for looking in! :beer: David D |
| PJW:
Hi Dave, I am watching with interest, I know nothing about vacuum engines so its look and learn. It looks like it will be an interesting engine when you have it running. |
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