Building the PM Research Number 3 Steam Engine PT2

The highlights of the PM Research #3 steam engine build continues. First, the work is started on the cylinder which features quite a few machining operations. Next, the machining of the eccentric and showing how that part is setup in the 4 jaw chuck. Lastly, wrapping up construction with the final assembly of the engine. A small video at the end of the article shows the engine running on compressed air.

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The core hole was well centered in the cylinder casting and looked straight. Taking advantage of this it will be used to help center the work in the 4 jaw chuck. Here at the drill press the cylinder is held with a clamp by hand and the core hole is drilled out to accept a dowel pin. By holding the cylinder loosely in this manner, the drill will follow the path of the existing core hole.

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The dowel pin inserted in the cylinder head. The size of the dowel pin is smaller than the final size of the bore.

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Using the dowel pin to setup the cylinder in the 4 jaw chuck. By initially holding the dowel pin in the drill chuck, you can get a good start on centering the cylinder in the chuck.

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The cylinder is faced on one side, then flipped around in the chuck and faced on the other side to size. Then the cylinder piston hole is bored to the final size with a boring bar. The cylinder face closest to the boring bar is the side that will be fastened to the base.

It’s critical that the base-side of the cylinder is bored and faced in one setup to insure that the cylinder bore and face are as perpendicular as possible.

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Drilling the steam passages. The wire provides a great indicator when you break through to the other passage.

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The bolt holes in the cylinder head were transferred to the cylinder with transfer punches. Here the little Cameron drill is used to open the punch marks.

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Over at the mill the holes are picked-up with the wiggler to be drilled and tapped. It would be easier to use the bolt hole function of the DRO, which should give an identically layout as it was used for drilling the holes in the cylinder head, but I prefer to do it the old fashioned way as I believe it reduces the chances of making a mistake.

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Making slots in the eccentric. Since the desired slot width is slightly larger than the cutoff blade width, a gauge pin is used to measure the width.

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Setting up the 4 jaw chuck to get ready to cut the actual eccentric bit of the eccentric. A dial indicator is used to set the depth as noted in the plans.

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Using the always handy tool post drilling jig to drill the hole for the set screw in the eccentric.

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Punching bolt holes in the gaskets using punch and die sets.

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All the bits machined and ready for final assembly.

I think hex-headed screws look better than the slot-headed screws provided with the kit for this engine and you can find 5-40 hex bolts for sale at this web site:

https://www.microfasteners.com/

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The completed engine ready to run. I also added a few brass oilers that were purchased from PM Research that were not part of the kit.

The engine running on compressed air.

The PM Research #3 engine was a fun build. The bronze machined beautifully and it looks great on the completed engine. While still a relatively simple design, this engine looks and runs more like full-sized engine than my previous builds. It also runs great at slow speeds.

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