Wednesday, 17 August 2011

Scratch built steam engine.

This is a scratch built steam engine that I completed 30 years ago. The design originated from a set of plans published by Model Engineer. If my memory serves me right it was described as a marine engine but I would class it more as a mill or factory engine. I made several modifications to the design but the major departure from the original was a doubling of all dimensions on the drawing. (and yes, it did cause problems.)

For the most part the machining and construction was carried out on my ancient leather belt drive Grayson three and a half inch lathe, (sadly missed). Milling was done using a vertical slide on the lathe. My drill press was machined from a set of castings and my bench grinder was hand made and powered by a washing machine motor.

No castings were used in the construction. With a few exceptions – nuts and washers for instance – everything was hacked from solid bar even the cast iron parts were cut from fine grained cast bar.

On completion, I ran it up briefly down the local pub on CO2 gas just to check the timing. It hasn’t been run since and for most of that time has lived in a toolbox wrapped in oily rag. Even so it had become very dirty in that time and rust was starting to show so a couple of days ago I set to and gave it a clean as best I could without dismantling it. The sump within the frames has a layer of brown crud that has set like varnish sealing in the dead critters and Christmas tree needles???? – don’t ask, I can’t remember!

I recently acquired an air compressor so I was looking forward to seeing my little engine in action again. I filmed it running and you can see the results here – just click on the link:

Technical detail:

• Bed or frame constructed from gauge plate dowelled and screwed with edge radii stone dressed by hand.

• Phosphor bronze double acting D valved cylinder with 1” dia cast iron piston.

• Piston “ring” and stuffing box glands fitted with traditional graphite cording.

• Cylinder lagging cover from shim stock – oiled and heated to produce blue “parkerizing” effect.

• Connecting rod partly machined then filed, stoned and emeried to a finish.

• 3.5 inch dia cast iron flywheel turned from a 4” dia bar.

• Runs (slowly but nicely) on just 10 psi

• Overall length approx. 12.5” or 32cm if you’re under 65

• Weighs in at 18lbs or just over 8 kg