Mike's Workshop Notebook

Westinghouse Water Pump

Currently on the bench is a single-cylinder Westinghouse-style water pump. The design comes from plans by Moodie E. Braun, originally published in the November 1984 issue of ModelTec Magazine. One of the features that really drew me to this design is the water-side valving. Instead of using a separate valve body mounted on the back of the pump, the valving is cleverly integrated directly into the walls of the water cylinder. It’s an elegant solution that simplifies the pump’s overall profile while still doing the job effectively. That said, working from the published plans has been a bit of an adventure. The editing leaves much to be desired, with a number of issues—dimension discrepancies, incorrect labeling, and a few outright errors. I’ve been able to identify and work through most of them, but not all. As a result, a few parts will need to be remade as things are sorted out. In hindsight, it probably would have been wise to 3D print the design first as a sanity check before committing it to brass.

Photos

Stock
Here’s the raw stock for the major components of the pump. The valve body will be machined from 3/4" square brass, while the cylinders, end caps, and spacer will come from 1.25" round brass.
Machining
The first step is cleaning up the bar stock and bringing it to size before starting any of the detail machineing.
Worthington Pump
Initial machining of the cylinders, spacer, and heads is underway. The bores were completed on the lathe, starting with a drill to rough them out close to size, followed by a boring bar to bring each one to its final dimension.

For this work, a collet chuck was used rather than a 3-jaw. It provides better concentricity and repeatability, which is especially important when boring—any runout at this stage carries straight through to the finished part.

This approach keeps things efficient while maintaining accuracy. Drilling removes the bulk of the material quickly, and the boring operation ensures the bores are true, concentric, and to size, with a much improved surface finish.

Worthington Pump
The water cylinder is shown on the left. Note the more complex internal and external cuts required to support the integrated valving. Similar features are machined on the underside as well, forming the internal passages that allow the valving to function within the cylinder walls. The piston in the water cylinder is double-acting, meaning it pumps on both the up and down stroke—drawing water in on one side while simultaneously expelling it from the other.

The steam cylinder is shown on the right. It includes five holes for the head bolts, along with two additional holes for studs that thread into the valve body and are secured with nuts on the opposite end. Also visible is the steam port, which directs steam to the lower side of the cylinder.

The steam cylinder and piston assembly is double-acting, allowing steam to be applied alternately to each side of the piston for continuous operation.

caps
Shown here are the end caps and gland nuts. This is one area where the issues in the drawings became pretty apparent. Several of the hole locations in the cylinders don’t line up as they should, so the heads will need to be remade.

Threading also turned out to be a bit of a lesson. Bottoming taps and dies were used for the gland nuts and heads, but with only a few threads of engagement, they didn’t cut deep enough to give a proper fit. As a result, these parts will be remade.

The plan going forward is to single-point the threads on the lathe. That should provide better control over thread depth and fit, and eliminate the limitations encountered with taps and dies.

valvebody
Shown here are the valve body, central plug, and freshly cut end caps. The central plug serves to separate the pilot valve chamber from the main control valve chamber. Once the plug is silver soldered in place, the valve ports will be drilled through, establishing the internal passages between the chambers and steam cylinder.
Pump
It’s starting to take shape. At this stage, enough parts have been made to allow a preliminary assembly and get a feel for how the finished pump will come together. Seeing the components in place is both satisfying and motivating.