Elmer Verburg's Pumping Engine
The picture above is a of a model I'm attempting to replicate. I've actually tried to talk myself out if it a few times. It is by far the most complicated model I've ever tried. I keep working at it a little at a time. Maybe someday I get it done.
So Far....
Originally I was going to make the cylinder blocks of aluminum.
The stock was easy to cut from a chunk of scrap I had on hand. The ports milled perfectly and the drilling of the ports went OK until I broke a 1/16" drill bit off in one of the 11 degree holes that runs from the outer port to the end on the cylinder. That was only the beginning of the problems. Tapping the 24 small holes that would accept the screws to hold the heads on was a disaster. The threads pulled in almost all of them, so I decided to switch the material to brass.
Here is the finished brass cylinder with both heads attached. The steam chest that will house the D-valve has also been made for this cylinder and is temporarily held on with 2 screws. The D-valve will slide up and down over a valve plate with holes that will match the ports seen in the picture above. Air will enter the cylinder block through the tapped hole in the side of the block that can just barely be seen by my thumb. That hole leads to the center port in the block. The upper and lower ports have holes drilled to them from the ends of the cylinder bore.
When the valve slides up it will complete an air flow path from the center port to the upper port, pressurizing the top of the cylinder pushing the piston down. When the valve slides down the bottom is pressurized forcing the piston up. It's a basic double acting cylinder.
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I always do what looks like it will be the toughest first, so I tried to make one of the yokes next. It went better than I had anticipated.
I started by cutting a slab off a brass bar and milling it to the finish overall dimensions of the yoke. The second picture shows the lay out of the holes for the inner radius for the 4 corners. After drilling the 4 holes the rest of the shape was drawn on with a scribe, and the the part was sawed, filed and polished to completion. The finished yoke is shown in the last picture with the piston connecting rod assembled to it. The quarter is for scale. The connecting rod is pinned in place with a brass pin that is 1/16" in diameter with a 1/8" head.
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Much More To Come!