Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Moving on with the new compression plates...

I used the mill to even up the edges of the sawed rectangles, and bring them to the correct overall size. I then clamped the rectangular plates in the mill to drill the .203" dia. center hole, and cut the .078" wide slots. Here's what the plates looked like at this point:

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Next, I had to re-blue the plates and scribe the 15 degree angled lines. I used my die filer to finish shaping the outside contours of the plates. For those not familiar, the die filer is a small machine which simplifies off-hand filing of 2D shapes. This particular one was machined by me from a Metal Lathe Accessories casting kit. If you're curious, you can check out this YouTube video: Xl0zrNYh41w Anyway, here is a view of filing the contours to shape:

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As already mentioned, the new compression plates are .031"(.79MM) thick, while the previous plates are .015"(.38MM) thick. Here is a side-by side comparison:

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In order to make the compression plates somewhat match the contour of the boiler, I gave them a slight bend, as you'll notice in the following pictures. To make the plates look more "antique", and stand out less on a 120-year old engine, I dunked them in some Brass Black to give them a dark finish:

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Here's what the finished plates look like:

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All that's left now is to assemble the sight glass parts. After threading the seal plates and o-rings onto the sight glass tube ends, an initial snugging of the screws indicated that I could use a bit more compression on the o-rings. I judged this by pulling out on the sight glass tube ends, and noting how much force was required to pull the the tube ends past the o-rings. I determined that I needed a bit more compression. This was also the case with the Doll vertical engine I recently worked on. As in that situation, I made some small brass shims. These are basically the same ID and OD as the o-rings, and .015" thick:

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I took a picture of one end of the assembled sight glass, with the screws just snugged, not tightened down. You can just barely notice the thin brass shim between the compression plate and the o-ring:

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All that was left at this point was to back off the screws a bit, apply some Loctite 542, and tighten the screws down. And here's the finished product:

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Paula