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Valve Gear

The Hall uses Stephenson link gear mounted internally between the frames, and the cylinders have piston valves.
Most of the valve gear components are straightforeward to make, although the eccentric strap might be worth a comment.
The first step was to machine up a bit of bar to 1 1/8 diameter, with a lead that was a few thou less - as a go/ no-go gauge, and also for use as a jig.
To machine up the eccentric,(from a casting), I sawed it in two, to form the two halves of the strap, then milled the surfaces square. I used a fine hacksaw blade, and was careful to mill off the least possible metal. Then I silver soldered the cut halves together again, and set up in the 4 jaw to bore the eccentric. (To set up work in a 4 jaw chuck, I use a dial gauge mounted on a tool holder, and TWO chuck keys on opposing jaws. This let me move the work together with the clamped up pair of jaws - much quicker and easier.
A simple jig made sure that all four eccentric links were the same length.
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