Simple Oscillating Steam Engine

This engine was designed following a number of requests for a simple machining project.

There are many other oscillating steam engine designs, and some are much simpler, using plumping fittings and wire links etc... However because this engine was designed to be a machining project, bar-stock was used for all the parts.


The design had several key features :

It used no castings and no brazing.

The piston, con-rod and big end bearing were machined in one piece for simple assembly.

Only a 3-jaw chuck was required on the lathe.









Click to Enlarge


A - Cap nuts. 3x 10 BA or similar

B - Bearing nuts. 3x 10 BA or similar

1 - Base Plate

2 - Main Axle

3 - Frame

4 - Cylinder

5 - Cylinder Cap

6 - Crank

7 - Crank Pin

8 - Main Bearing

9 - Cylinder Pivot

10 - Pivot Nut

11 - Piston Assembly

12 - Flywheel









Although simple, this design does assume the builder has access to a small pillar drill, lathe, drill set and some hand tools including files and marking out equipment. However the instructions are quite comprehensive and don't assume the machinist has any prior knowledge.

The menu below details the manufacture of each component in the order they were made.









Base Plate

Main Bearing

Main Axle

Cylinder Pivot


Pivot Nut


Piston Assembly

Cylinder Cap


Crank and Crank Pin











Assembly, Running and testing the engine.










Click the image on the left to download a PDF file of the engine plans


.... and if a boiler is needed to run the engine the plans on the left detail a simple horizontal design which is fueled by solid fuel.

Construction notes for the build can be found here
Finally. This link contains details for constructing both the boiler listed above and a steam lunch which can put the whole steam plant into action.



Since publishing these plans lots of people have sent in pictures of their engines based on this design. Click the image on the left to view the gallery

All images shown with owner's permission.