90 Ton Mikado, Page 26


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3/23/8 Branch Pipe Jackets

It amazes me how few people know how a steam locomotive really operates - I mean on the really fine-scale detail, such as how the valves are supposed to operate. (includes myself) Most of those who knew are long gone. And as expected, there is a lot of folklore going around, most of which is either misguided or just plain wrong.

Besides the P-V example, here's another case. Branch pipe jackets -- what are they for? Are they cosmetic? - or do they serve a useful function? The erecting card shows them, but what do they do?

From what I could get on the message boards, these are to protect the branch pipe insulation, which is necessary to reduce heat loss to the weather. It was also pointed out that the cylinder "dress up" sheet is not for looks either, but to cover the insulation over the cylinders for exactly the same reason.

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Image 159 -- Branch Pipe Jackets and Flanges and the Tools to make them.

The jackets cover the branch pipes which exit the smokebox at a steep angle. They are bolted to the smokebox with a flange. In the photo above, you can see both the jackets and the flanges although they are not welded together yet.

The flanges are shaped to fit the curvature of the smokebox. I used a trick I learned from Jesse Livingston (alias Uncle Jesse). Use a pair of wood blocks as a former to bend the flanges. - Works great. Also the pipe holes had to be filed to allow the pipes to pass through at the steep angle.

The upper end of the jackets need to match both the angle and the curvature. Try as I may, my computer generated template failed. Oh sure, I could eventually get that to work. But forget it. Make a live template out of cardstock and be done with it.

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Image 160 -- What the Jackets Cover + Piston Rod Gland.

Here's the branch pipe, and the Tee from the oiler the jacket is supposed to cover and hide. I made collars that are the inside diameter of the jackets to support them at the bottom (shown here).

Also remember the piston rod glands mentioned in the last page? Here you can see one installed.

3/23/8 Branch Pipe Jackets - complete and installed

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Image 161 -- Branch Pipe Jacket -- installed.

These fit so well only 2 screws are required to secure them. I need to sand and repaint them.

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