Crosshead and Wristpin

The original plans called for a straight wristpin and straight hole in the crosshead. The bore in the crosshead was to be a slip fit with the pin. In this condition, the pin is already loose.

Due to the seveare amount of beating these parts get, I decided to re-design the parts following the prototype. The wrispin has two (concentric) tapers that bear into two corrisponding tapers in the crosshead. I modeled the parts to assure a good fit and then produced the drawing. I made the wristpin first, using the compound set at the proper angle, and then made the bore in the crosshead without moving the compound. I used the completed wristpin to test the bore for the proper size.

The 'proper' angle of the compount was set using a known X distance figuring the amount of Y distance measured on a dial indicator.

Crosshead View            

This is a view of the crosshead, view from the front, and wristpin with the crosshead transparent to show the tapers. The collar on the left is used so the nut on the wristpin bears on the crosshead to tighten the tapers. The outside diameter of the collar should be the running fit for the Union Link.

Crosshead and Wristpin Drawing

Here is the drawing for the Crosshead, Wristpin, and Collar.

Karl Kobel

With the help of Matthew Kobel and Gordon Carlson (see his work at