double acting oscillating cylinder engine

Hi All

My next steam engine will be a simple double acting oscillator, 5/8" bore 1" stroke.

I want to fabricate the cylinder in much the same way as Jason did in his new year oscillator by silver soldering the parts together. see photo below.

M Machine metals have LG2 gun metal in hollow and solid round, a material which I would favour for most of the fabrication. no particular reason I just like the material and as it is used a extensively for cylinders thought I would give it a try.

I assume gun metal ok for silver soldering, if so what grade of solder?

The piston material, cast iron? phosphor bronze? aluminium alloy? gun metal?

Any thoughts/comments as ever would be welcome.

thanks Geoff

Hi Geoff,

For the oscillators I have made with a copper-alloy cylinder, I have used free-cutting stainless steel for the piston. My advice would be to use a different material for the piston, only exception I have made is Cast Iron cylinder and Cast Iron piston.
The parts in your photos look well made, good luck with the build.

Thor

Hi Thor,

Thank you for the reply, some good advice.

I find the issue of which materials to use confusing and would expect people to have different viewpoints largely based on their own experience.

My experience is limited to two engines both of which had a cast iron cylinder and a gun metal piston. they have both worked well and my thoughts were that you could pair them the other way round, gun metal cylinder and cast iron piston, but I don't really know whether that is practical.

I feel I should point out that the well made parts in the photo are not mine, they are Jason's work from his new year oscillator

thanks again Geoff

Hi Geoff,

A cast iron piston in a gunmetal cylinder should work well. If you intend to run your engine on steam a stainless steel piston is less suspectible to corrosion than cast iron.

Thor

I tend to use aluminium 6062 (HE30) for my pistons as the lighter material means you don't need much if any in the way of counterbalance weights on the crank. Single Vitron O ring will work with that. No ring needed for air running.

You don't need anything with a high melting point so 55% solder will do, if you have some old Easyflow even better.

I used bronze for most of that cylinder except the end flanges which are brass as I had quite a bit of that in stock. Leave the flanges 0.5mm over thick and the cylinder spigots about 0.3mm over that way a bit of studding through the middle and a couple of bars each end will hold it all together while soldering. Also leave bore 1.0mm under and then you can machine it all up to finish size once soldered.

Description of another similar cylinder here