It woud be best to put some 3 in 1 or other light oil on the wet and dry to stop it clogging and to get a cleaner finish. Soapy water can help too if nothing else is available.

A local glass merchant might be able to sell you a square of 1/2 in plate glass but unfortunately many only stock laminated now. If that is put one something reasonably flat it can make a good flat surface. 16mm mdf is often very flat, also pieces of kitchen surface. Those are easily checked with a rule.

Rather than wet and dry you might like to try some papers 3M make. They are are actually a plastic film for lapping and finishing and go down to sub micron levels. A number of companies offer sample packs but i suspect the best value ones are from cousinsuk.com. There's are full sized sheets. They are a watch and clock bits type company also useful for acids if you are local to them. The papers are mostly being used by woodworkers to get tools amazingly sharp at the moment but should have uses for all sorts of finishing.

John

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Edited By John W1 on 18/07/2015 17:10:54

60psi sounds a bit excessive !

Could be that air is getting past the piston and out the exhaust that way too.

It sounds like it could be a stuck valve as Jason suggests.

Also, does the engine turn over freely if you spin the flywheel. An engine that will run on air and not be expected to do a 'job of work' will benefit from being fairly free-running, although things will improve with an hour or two of use.

Neil

Peter On larger steam engines the valve closes before the piston reaches top dead centre and the steam expands still driving the piston This is usually refered tto as ' cut off ' Air does not expand Also on large engines witha condenser a vaccuum is formed on the other side of the piston which sucks the piston So to answer your question the answer is yes but in small sizes I don't think it's going to matter that much

Roy

When I was an apprentice one had to produce three flat surfaces starting with files engineers blue and a surface plate then by lapping this was done on three pieces so that one didn't get a concave on one mating with a convex on the other Apprentices where taught to do this before being let anywhere near the machine shop A lot of ' fitting ' was done by hand after work had been machined

Ha the good old days ! !

Roy ( Nostalga isn't what it used to be )

Thanks Neil,

Yea I was planning on facing in the lathe, it's far from ideal but the last little job I did that way turned out better than I expected.

I'm reading as much as I can online about steam engine design but don't seem to find out a great deal about how to lap, get decent seals, gland packing etc in model engines

Peter.

If you can't get a bit of plate glass, go to a second hand shop, and get an old, heavy plate glass mirror thick as you can get, you might have one around the house that has damage to the mirror backing.

Ian S C

Phil

Make a tapered sleeve that the small end is a nice sliding fit on the piston, soak the yarn in warm oil fit in grove enter the piston down the taper and lightly hammer into the cylinder bore using a piece of hard wood.

Stan