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.
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.
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 http://www.locogear.com/page15.html).