Kozo's Pennsylvania A3 Switcher in 1.5" Scale

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Jul 24, 2020
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Howdy folks, in this thread I'll be documenting my progress on my first live steam locomotive: Kozo Hiraoka's A3 switcher. I started in 2017 with no machining experience, and have worked on it sporadically since. I was quite inspired by Kvom's build of this locomotive, seen in this thread: Kozo A3 in 1.5" scale

Progress up to this point can be seen here:

Unfortunately, I couldn't bring my increasingly heavy project with me when I moved up to Alaska 8 months ago. Canada's Covid restrictions meant I had to fly up here on an airliner. But I'm feeling the need to work on it again, so I'm having the locomotive crated and shipped up here via UPS! The amount of time and effort I've put into it makes the shipping costs worth it for me.

In the meantime, I started work on the cylinders. Kvom used the Yankee castings, but I decided to do it "by the book" and make them from solid iron stock. So far I've enjoyed the process immensely. Here's the 4" diameter round bar that showed up in the mail:

I bought ductile iron instead of the typical grey iron, since I found a better deal for it online. It machines nicely, turning into chips instead of dust like grey iron. We cut the bar with a cold saw that's only rated for 1/2" thick material, lol. The next step was to mill the outer profile:


Next, scribed and punched a mark for the bore. We then used a wiggler and indicator to center the bore mark in the 4-jaw chuck:

Turned the shoulder, then drilled and bored the cylinder within tolerance to 1.750+.002". Once that was done, we flipped the piece around, indicated off the finished bore to re-center, and turned the other shoulder.

The cylinder up to this point:

I figure about half of the cast iron I started with will end up as chips by the time I'm finished! More cylinder work to come.
Still time to correct two errors in the plans that caused me the most trouble.

The foot plate length was not scaled properly so that the holes for the walkways are too close to the centerline. So when you build the yokes to plan the mounting holes don't line up. Several ways to correct this.

The steam dome on the boiler is in the wrong place.
Thanks Kvom, I'll keep an eye on the yoke mounting holes. When I met Jesse Banning he said the same thing about the steam dome... what exactly is the issue? Does it need to go forward or something?
Hi I built Kozo Hiraoka's Shay in 1.5 scale (from his first shay book) his writings and drawings I found to be very good.
I look forward to your postings on it I'm sure you will end up with an excellent loco

Great video and amazing job on the cylinder. I'll be watching from Texas.

How do you like my avatar?
I like your profile pic Dad!

Quick couple hours in the shop today, machined the steam port and frame mounting faces to their proper dimensions. Got the corners as close as I could without cutting into the heads...

One other thing as long as I'm thinking about it. If you are going to make the boiler from steel, then it's a good idea to have blowdown valves on both sides (so you'd need another hole in the frame).
Thanks Kvom! When I built the frame several years ago I drilled a blowdown hole in each side.
More progress on the cylinders... machining the steam ports took an excruciatingly long time with a 1/8" carbide endmill, but I managed to finish them without breaking it. Don't have any R8 collets, but the drill chuck worked just fine...

The plans don't specify how deep these ports need to be machined (error?), so I eyeballed it and milled about halfway to the bore (0.425"). Here's the two cylinders with their ports milled:

I also drilled and tapped some holes where the cylinder will mount to the frame/steam tee. Interesting to note that all the exhaust ports and passages are double the size of their steam admission counterparts. I guess you don't want the engine choked by its own exhaust.

Next came a fairly stressful operation, setting up and drilling the various steam passages. I'm happy to say that if you follow the book and use the specified angles, it'll work out just fine. I definitely triple-checked before drilling anything though! Here's the exhaust passage drilled through:

And one of the steam passages to the end of the cylinder. You can see the angle blocks we used to set these up; we decided to use 25 degrees instead of 28 in the book because it gave us a little more wiggle room.

The hard parts of the cylinders are done; all that's left is to drill/tap the heads, sand the port faces, and remove excess metal from the outside of the cylindrical portion.
Over the past few days I finished the cylinders. First came drilling and tapping the heads, using the DRO to locate my array of holes:

Next came whittling down the cylindrical portion. Kozo suggests making a mandrel in the lathe, mounting the cylinder to it, and (with the lathe shut off) running a parting tool sideways to scrape off strips of metal. That sounded like too much work, so I just used the mill vise:

I was able to get it pretty close by eye, knocking down each peak until I had many segments forming a curved surface:

The final step was to sand the port faces smooth to the touch, to provide a good surface for the valve to slide on. Here's some pictures of the completed cylinders! I will come back and try to smooth out the curved surface some more (the machining marks on the first one are still pretty bad), but it's purely for looks. My goal is to make a locomotive that runs first and looks good second. Regardless, I'm happy to see these completed!