Another Triple Expansion Steam Engine?

by John

Julius deWaal has drawn and published plans for model engines, most recently the Bolton/Bertinat plans for the triple expansion marine steam engine. The triple plans are available to download free of charge at ….

I made a model triple using the Bolton plans and castings, several years ago.

Here is a recent photo of my model triple expansion engine operating on steam at the Royal Geelong Show. In the background is a full size version, which is a permanent, operating, attraction at the show. My model is 250mm long, 250mm high, and weighs about 10kg. It has a Stephenson reversing mechanism, and an exhaust steam condenser, both of which work.

It was a difficult build, taking me about 3 years, with a couple of sanity restoring long breaks during which I built other models. The build was detailed on this blog. To check the progress photos and descriptions do a search on “triple”.

I was very happy to finish the build, and ecstatic to see it working on compressed air, and then steam. When exhibited it always attracts a lot of attention, with its myriad of small moving components.

But, I was a bit unhappy, because it does include some errors. These were partly due to the suboptimal plans, and more so to my inexperience. The errors are not apparent to a casual observer, but I know that they are there. They do not interfere with the operation on steam. I had considered making another, bigger, triple, but always backed away, due to the time, complexity, and cost.

But a friend recently sent me a link to the new deWaal plans. The link is below the first picture, above. The new plans are metric, very detailed, and TWICE the size of the originals…. i.e. a model built to the deWaal specs would be 500mm long, 500mm high, and probably weigh around 40kg!

I must be a glutton for punishment, or a bit nuts, because I am seriously considering making another triple, using the deWaal plans and not buying castings but using bar stock. And maybe using some home made castings.

So, watch this space…..