Bob Sorenson
Well-Known Member
This project is the Stuart Turner #5a stationary steam engine from a casting kit. The 5a is the largest single cylinder kit in the Stuart line (Stuart Models | Steam Engines | Model Engineering | Executive Toys). It has a 2.25” bore, 2” stroke and 7.5” diameter flywheel. Here is a fine example of the 5a.
I plan on adding the Stevenson reverse mechanism, as shown above and a mechanical lubricator. Might add a second lubricator for the main bearings and trunk guide, we’ll see. At the time of this writing, the rotating assembly is done, and it turns great. ()
Unlike other Stuart kits, the 5a kit is castings only. There are no other materials, fasteners, or supplies. The threaded parts are all British standard, mostly 1/4” BSF and 2 British Association (BA). Since there are no fasteners, I decided to go with the Unified Thread Standard equivalent, which is ¼ x 28 and #10 x 32. The casting kit comes with a set of plans. The plans are a (probably 1/3) reduced photocopy of the old school vellum blueprints. They are mostly legible.
Get started with the base casting. Start off by trimming up the bottom to clean metal. Don’t take too much off, there is not a lot of height “meat” on this part. Be sure the 7.5” flywheel has room to turn. There was some “chill” on this bottom edge, however, a carbide cutter went thru it.
Use a 1” diameter pin to probe the corners and the mounting lugs. Tap the casting around until centered.
The base casting is not shown in the plans. Match the hold down bolt pattern from the sole plate. Tap with ¼ x 28.
The mounting lugs turned out to be 7-7/8” apart. At first, I drilled for ¼” hold down bolts. Later expanded to 5/16”. Mill off the mounting lugs to about ½” thickness and deck off the base to clean metal.
Enough for today. Next time starts on the sole plate.
I plan on adding the Stevenson reverse mechanism, as shown above and a mechanical lubricator. Might add a second lubricator for the main bearings and trunk guide, we’ll see. At the time of this writing, the rotating assembly is done, and it turns great. ()
Unlike other Stuart kits, the 5a kit is castings only. There are no other materials, fasteners, or supplies. The threaded parts are all British standard, mostly 1/4” BSF and 2 British Association (BA). Since there are no fasteners, I decided to go with the Unified Thread Standard equivalent, which is ¼ x 28 and #10 x 32. The casting kit comes with a set of plans. The plans are a (probably 1/3) reduced photocopy of the old school vellum blueprints. They are mostly legible.
Get started with the base casting. Start off by trimming up the bottom to clean metal. Don’t take too much off, there is not a lot of height “meat” on this part. Be sure the 7.5” flywheel has room to turn. There was some “chill” on this bottom edge, however, a carbide cutter went thru it.
Use a 1” diameter pin to probe the corners and the mounting lugs. Tap the casting around until centered.
The base casting is not shown in the plans. Match the hold down bolt pattern from the sole plate. Tap with ¼ x 28.
The mounting lugs turned out to be 7-7/8” apart. At first, I drilled for ¼” hold down bolts. Later expanded to 5/16”. Mill off the mounting lugs to about ½” thickness and deck off the base to clean metal.
Enough for today. Next time starts on the sole plate.