Kozo K-27 Crossheads and Pistons



This construction segment will concentrate on the pistons, piston rods and crossheads. The photo of K-27 463 is provided for reference.


These six pieces will make up the main portion of the crossheads. The thicker block will be sandwiched between two plates and then the assembly will be soldered together. September 26, 2020.


The components for the two crossheads have been silver soldered with the one on the left still showing the temporary retaining screws. The first cuts have been made on the piece to the right which include the drilling and threading of the piston rod hole along with a round shoulder. There will be many more cuts made to get these to the final shape and mount the brass shoe at the top. September 27, 2020.


The piston rods have been machined out of stainless steel and threaded into the crossheads. Nuts for the piston rods have also been machined out of 3/8" hex stock and are used to lock the rod at the correct length when the piston position is adjusted. The brass shoes have been cut and will be mounted in the top of the crossheads with five screws. Once that is done the shoes will be milled to the correct height using the rods as the reference point. October 4, 2020.


The brass shoes have been machined to be parallel to the piston shafts and milled to the correct thickness to fit between the guides. October 11, 2020.


Holes for the main rod bolts have been drilled and reamed. A short chamfer has also been milled at 45 degrees on the lower edges near where the piston shaft threads in. The next step will be machining two arcs on the rear of the crossheads to bring them to the final shape. October 11, 2020.


This evening one of the crossheads was milled to the final shape with three different arcs at the rear. The length of this assembly is just over 5 1/2". Note that the hex socket screws will be replaced with hex head fasteners in a future step. October 11, 2020.


Both of the crosshead assemblies have been finished to the final shape. October 14, 2020.


The first piston has been machined with a diameter of about 1.3". The o-ring is an AFLAS which is able to stand up to higher temperatures, steam and oils. October 18, 2020.


The two pistons have been completed and also pinned to the piston rods. A screwdriver slot was also cut into the piston end of the rod to allow for length adjustment once mounted in the cylinders. The next step will be the machining of the crosshead arms that attach at the main rod hole and will attach to the valve gear. October 24, 2020.


The crosshead arms have been machined with the pin fitted and soldered to the arm. The next step will be to accurately position the arms 10 degrees from vertical and then drill the mounting holes in the crosshead. Here we see one of the arms set on a temporary pin in one the crossheads to provide a visual of how the pieces fit together. November 8, 2020.


This afternoon was spent making the custom crosshead bolts that will replace the cap head screws in the prior shot. On the right we have a sample of the first machining work performed on the lathe. In the middle is the hex head formed by machining in a hex collet block on the mill. At the far left is the final machining on the lathe to provide the appearance of a bolt end sticking out through a nut. November 15, 2020.


The ten custom crosshead shoe bolts have been completed to appear like a bolt sticking through a nut as seen above. One of the crosshead pins has also been machined that will attach the main rod to the crosshead. A second will need to be machined and then hardened to take the abuse. December 13, 2020.


Both crosshead pins and the custom size nut have been machined and used to help locate the crosshead arms on the assemblies. The crosshead arms are canted 10 degrees from vertical and the mounting holes have been drilled and tapped. Now I need eight custom bolts to get rid of those slotted screws. December 19, 2020.


The eight custom bolts for the crosshead arms have been completed. December 23, 2020.


The piston and crosshead assembly have been completed and test fit on the locomotive. December 23, 2020.


The progress to date with pistons and crossheads fitted to the assembly. December 23, 2020.