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Webster IC Engine build log.
raynerd:
Oh Dear, what an idiot I am :palm: Brilliant, that makes perfect sense with the C-o-C, thank you !!
Ahh this makes sense also what you recommended in a 3/4" bore and 1/16" cross section...
1/16 + 3/4 + 1/16 = 7/8" !!
O-------O
OK - I was definately slow on the uptake of this one!
So as Nick suggested, my closest is going to be the 11/16" inside diameter with 3/32" cross section to give me the 7/8" OD I need?
Chris
Bogstandard:
Sometimes you can't see the trees because of the forest getting in the way.
Everyone gets mental blockages, just that mine now seems permanent.
So what you should do now is to make your ring groove in the piston a couple of thou shallower than the cross section of the ring, that will give you the deformation pressure to ensure the OD of the o-ring seals against the cylinder wall. Eventually it will wear a flat on the outer face and act just like a normal piston ring. When you start to lose compression, pop a new o-ring in, and start from scratch again.
Bogs
NickG:
:doh: :bang: :smart: :lol: Glad it's not just me then!
madjackghengis:
--- Quote from: NickG on January 25, 2011, 11:48:22 AM ---Chris, there is a lot of debate over this subject! I think there might be some info in the tiny i.c threads too. I'd be tempted to go for a lapped bore and cast iron piston with not much clearnace. I know Jan Ridders does that on his engines.
--- End quote ---
Hi Chris, as a matter of fact, boring on a table with the bar between centers is far and away the most accurate way to bore, and misalignment of the bar only affects the roundness of the bore, and does so absolutely equally the full length, and takes lots of misalignment to make a noticable difference. That said, having made a very straight and accurate bore, the idea of lapping and using a very close fitting cast iron piston would seem to be a more accurate way to get where you want to be. The reason for the odd sizes on the grooves for a viton o ring, is to allow compression of the o-ring, while giving plenty of room for it to expand laterally, so the rubber is not compressed, but merely displaced, and causing much less friction. An iron piston in an iron bore expands at the exact same rate for both, and keeps what ever clearance you have consistent, regardless of the temperature, and the graphite nodules in the cast iron make it self lubricating to a very large degree, allowing for very close clearances. :beer: cheers, mad jack
raynerd:
Hi Jack, thanks for your input regarding the piston seals. I`m not happy with the base material and so until I can save up a little cash for an all base (I`ve spent far too much this month to buy ANYTHING), I`ll just keep some bits on hold. Consequently I`ve made a start on the gears. I`ve made the buttons and holder this evening and I`ll take the buttons to work and harden them. Then hopefully in the next few days I`ll cut the cutter and then by weekend should aim at having a start on the first gear. I hope my calculations are correct, I`ve used mainly John Stevensons gear article, I think I`m in control....
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