Single Cylinder Compound Steam Engine

2026_10_10:  For the total masochists here's a link to the original plans if you would like to machine one from barstock: https://www.myheap.com/images/stories/Metalworking/Resources/downloads/ElmersEngines_byElmerVerburg.pdf

2020_04_07

--Once upon a time, possibly in the 1890s, someone mentioned this type of engine in an early edition of Model Engineer magazine. 40 years ago Elmer Verburg designed a miniature version of that single cylinder compound steam engine and got it published in the October 1988 issue of Modeltec magazine. It's not very efficient at the scale it was drawn but it illustrates the principle of compounding. A pal and I built a pair of these out of aluminum and brass and they worked just fine on steam. I've redrawn the plans so the parts can be printed. Once they come off the printer threads will have to be put in manually and they range from #2-56 up to #6-32 plus some odd MTP threads that my CAD program can't parse. I'll post a photo of the finished engine as soon as I can remember where I put my copy of the original!

2020_10_09:

-Replaced Base.stl with Base_02.stl, which is hollowed out to print faster with less material.

2026_09_25: 

--I've been doing a total re-think of the design because the smallest parts are really too small to be rendered adequately with 3D printing so something needs to change. One way would be to carry on at the 1-to-1 scale of the original and replace the tiniest parts with brass screws and other bits machined to the tolerances needed to make it work correctly, meaning folks would need a lathe at least. Plan B is to scale it up a bit so that a printer can do all the bits and that's what I plan to do. I'm going to  scale the thing up to 150% and redraw all the components. In addition to the size change I'm going to adjust all the holes to use metric, rather than SAE bolts so more people can find what's needed to put it together. The added benefit of increasing scale is the engine will run better at the larger scale. So far the only part I've redrawn is the cylinder but more parts will follow next week. I'm heading to  a steamboat regatta this weekend; toot-tooot! :-)

Category: Engineering