21: crosshead

The CK Holliday’s crosshead is fairly typical of the period, using a 4-guide rail type. The guide rails are bolted to the rear cylinder cap and the “yoke”, which is the same piece/casting that supports the bottom boiler brace (not the boiler braces on the pilot deck!).

Here are pictures of the crosshead assembly, both real and modeled.

In the above shot, the left crosshead is seen upper left, and the right hand crosshead is lower right.

Here’s the crosshead in its rails with some parts made see-through to better understand how the crosshead is built.

It’s a fairly straightforward part. There’s a center casting with a socket to receive piston rod. The center casting has a cast-in pin that is used to drive the connecting rod. It also has “wings” that are made to ride the guide rails. Fitted between the guide rails and the casting are “gibs” which are thin brass wearing surface.

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