Cylinder Bore 7/8" at a depth of 2.5" OR use DOM/CRS ?

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Bogstandard:
I think you would be much better off at this time using Viton rubber o-rings. They are a much easier solution for the Webster, rather than trying to learn all the pro's and con's of metal piston rings.

Get yourself a working Webster first, then on say your next build, try for a metal ringed option on another type of engine. Getting it wrong first time around could easily lead to a non runner.

sbwhart:
Some great information their John when to Hone and when to lap and what rings to use with each method.

Chris I'd go for the the viton ring method for a first build, I looked into cast iron rings I think its one of those things where you have to have the right techniques along with a big helping of nack.

Stew

raynerd:
OK, thanks a lot, John, Jason, Stew. I`m glad you have suggested that - making CI rings does look a bit tricky for me!

http://www.btinternet.com/~sylvestris/rings/rings.htm

....and John, thanks for posting your advice - :beer:, I appreciate it. I`ll let you know how I get on! I hope you think the Webster is a decent choice for my first IC build. It looks simpler than most.

Bogstandard:
The Webster is a very good first engine, easy to make and not much to go wrong. Plus running engine builds have been well documented.

Another one to consider is Jan Ridders two stroke that uses a vapour carb. A much larger engine altogether.

http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_tweetakt_motor/tweetakt_frameset.htm

John Somers is currently building one, but had trouble getting it started, but when I last talked to him, he said he had mistakenly drilled a transfer hole too small, so he might have got it running by now.

http://start-model-engineering.co.uk/category/jan-ridders-simple-two-stroke/

You start at the bottom of the page and work your way up.

Dean W:
Hi Chris;
I think you've got good advice here, especially with Bogs' comments, (yes, all of them ; ).
I can offer my two bits, just for something else to think about. Since the bore for your cylinder goes all the way through, you can
align bore it and have a very good chance of getting a true bore. The setup looks something like this:

A bar held between centers, which has a cutter held in a small hole somewhere near the middle of the bar.

Your work piece is first drilled undersized through the center, then mounted to the cross slide on the lathe, shimmed up as needed.
Just another way of skinning the cat.

--- Quote from: craynerd on December 30, 2010, 10:33:30 AM ---I have to admit, piston rings are always something that have confused me despite seemingly being fundemental to most engines!!! I can`t quite understand what they offer over a good fitting piston directly in the cylinder!!

--- End quote ---

The piston rings do something the piston cannot do. They can run against the wall of the cylinder bore with no clearance tolerance.
The piston has to be smaller than the bore, of course, or it simply would not be able to enter it. Rings, being flexible, can run against
the bore doing the gas sealing chores for good compression in your engine.
They do other things, but being able to run right against the bore makes them a pretty handy thing.

Good luck with your build!

Dean

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