Thoughts on aluminium cylinders

[kev]

Im looking to build a mill engine with a 1 inch bore, in the design the valve box is machined out of the same block so it starts as a 2 inch square.

All okay other than the thought of all the swarf and oil based coolant from machining a block of steel down.

Thoughts moved to making the cylinder from ally (the hard type), not the best of match's though an ally cylinder and a brass piston.

any thoughts or experience guys?

[Jasonb]

Machine from a block of iron then no coolant needed, you still get the swarf as you would with aluminium but that needs a cutting fluid too.

[kev]

I use meths or wd40 on ally which is "clean" compared to cutting oil, but the iron lump is a good idea, never bought large lumps but im sure its available

[Jasonb]

Yes most of the ME suppliers will do blocks, square or rectangular bar. Did this one a couple of months ago, 1 5/8" bore

[Arbalest]

I asked a similar question regarding Vacuum engines. The general consensus was that an Alloy cylinder works fine with a brass piston. Not tried it yet though. Cast iron may be stable and self lubricating but I'm not a fan of rust! I think Stainless Steel for both components was also mentioned as a suitable alternative?

[arnoldb]

If you're going to run the engine on compressed air, an Aluminium cylinder and brass/bronze piston will work fine 

For live steam, things change a bit - the high heat conductivity and relatively high expansion rate of an aluminium cylinder block could cause problems and is inefficient.  The same for hot air or stirling engines.  Even so, my Lamina Flow engine has an aluminium block and brass piston and works just fine, so don't worry too much 

Kind regards, Arnold