Bog's Paddleduck Engine

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kvom:
Better progress today in a short 90 minute session. I finished the glands for the valves, where previously I had made the gland and screw. Tonight I drilled and reamed the through hole for the valve stem as well as the two mounting holes. I was apprehensive about this step, but all went smoothly.

Although I didn't see anything in the plan about where to drill the mounting holes in the steam chest, John's photo shows them fore and aft. That's a job for another day, as well as lapping the valves into both the glands and the valve bores.

kvom:
Today I managed to get the valves lapped into the steam chest valve and drilled/tapped the holes for the glands. Otherwise too much time occupied with family visitors.

Bernd:
Hey at least your making progress. Mine seems to have come to a hault here. :(

Bernd

kvom:
Today I milled the steam slots that connect the steam chest holes to the block holes. As mentioned in a previous post, it's possible to mill the slots in the block rather than the steam chests, and that's what I did. I used a 1/8" endmill cutting .11" deep.

I also made V3 of the pistons, this time threaded 10-24 for a stronger joint with the piston rods. The other end of the rods are 8-32 for connecting to the crossheads.

I managed a better fit on the pistons by taking tiny cuts on the lathe. One is already a tight slip fit on one cylinder; the other will require some more polishing. If I can get the pistons lapped I'll drill and mount the glands next.

kvom:
I lapped the pistons so that I have a good sliding fit. I tapped the hole in the crossheads to accept the piston rods, and assembled the block and top plate to the bottom with one piston in its cylinder and the rod screwed into the crosshead. Although the mechanism operates fairly well (able to turn the crank by hand), there is an obvious issue: at TDC the piston protrudes through the top of the block. :scratch:

Since I had made the piston rod to the same scale as the rest of the parts, I am wondering if the 75mm on the drawing is correct. I checked the rest of the critical elements (stroke, length of conrod, height of columns, height of bearing blocks), and all seem correct. Doing some measurement of the piston postions I concluded that my piston rod is .45" too long, corresponding to 7.5mm off the plan's size.

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