Oscillating Engine on Steam

It is always exciting to see builds of our engine plans, this one especially so as it will be the oscillating engine on steam. Up until now I have only run this engine on compressed air. This build is by Michael Prady and this is a great mix of original design, changes in materials and additional design features.

With Michael’s permission I have posted the images and words from our correspondence as I think this just shows a wonderful approach to building this engine.

Michael Prady oscillating engine

I originally saw your engine on Pinterest and just followed you from there, my wife bought the pdf drawings from you, but I decided to build a boiler and economise feed pump first, the boiler is hydraulic tested to150psi, so a safe limit of 75 on steam, however I have the safety valve set at 50psi.

I’m putting a superheater in the main steam line as I think it’s too far for wet steam especially as it’s running a displacement lubricator too.

I’ve just modified slightly, as you can see it’s the opposite way round to yours, it should mean it just runs in the opposite direction.

We had a discussion around the piston rings as I show them in the plans, but I have to be honest and say that I never fitted them to my engine…..Michael’s solution to this is rather cool and reminds me of ET Westbury’s approach to piston and liner pairs.

I have honed the cylinder out to 0.5925inch bore, removed the bronze piston and replaced I with a solid cast iron piston of 0.592inch, it is a beautiful fit and both should expand at the same rate, the proof will be in the pudding if it runs.

Michael Prady oscillating engine
Michael Prady oscillating engine - displacement lubricator

I have thrown together a little displacement lubricator out of brass tube and scrap ends, it was dead simple and cheap to make.

Manifolds are fitted, she runs very sweet on air, got a beautiful exhaust beat.

Michael Prady oscillating engine

We will add to this soon….

Leave a comment