Revised Feb 18, 2013 Subject to Revisions
Valve Rod Set as Designed With Alibre 3D CAD
Valve Rod Set as Printed with the 3-D Printer
The above photo shows the valve rod set immediately after being printed. The part definition is good. the longer rods are about three inches long and the shortest is a bit less than three quarters of an inch. Some of the smaller rods have a wide section to provide enough material for tapping. The two inch long valve shafts are round with a U shaped end to hold the combination lever. Those are at the bottom left side of the print. Just above are the combination levers. At the top are the long radius rods. On the bottom right side the two shortest rods are the lifting links. Between them and the radius rods at the right side are the union links.
The Set of Rods After Removal From the Printer Raft Before Cleaning
The rods were readily removed from the printing raft of green ABS. Small amounts of raft residue are visible. It was relatively easy to remove the raft residue using the Dremel tool sanding wheel and model knife. The parts are very thin and fairly small. Despite their smallish size, the printer did a good job.
Outside portion of the Crosshead During Tapping
The outer portions of the crosshead were removed then drilled and tapped for 00-90 screws to provide the attachment point for the union links. The above photo shows one with the tap in place. Tapping was done by hand with just the tap, no tap holder. It is relatively easy to turn the small tap in the ABS plastic. A number 65 drill was used to drill the tap hole. That size is just 0.035" in diameter and is easily misplaced or lost if one is not careful.
Fireman Side Valve Rod Set in Place
The full set of the fireman side valve gear was assembled using a number of 00-90 screws and installed on the model. The thin radius bar at the top passes through the center of the curved expansion link and attaches to the top of the combination lever at the left and the lifting link at the right. The combination lever attaches to the valve stem near the top just below the connection to the radius bar and at the bottom to the union link. The union link connects the bottom of the combination lever to the crosshead. The lifting link at the top right will connect to the lifting arm attached to the reversing shaft after it is installed. The lifting arms and reversing lever and shaft will be built and attached a bit later in this blog.
Engineer Side Set of Valve Rods and Levers and Crosshead Cover
The rod set consists of the short lifting link at the top of the above photo; next below it is the union link, then below it is the combination lever. Below that is the valve stem then the long radius bar. Finally at the bottom is the crosshead cover and an example 00-90 screw. The various rods are drilled either for clearance of the screw or for tapping the threads.
Assembled Engineer Side Valve Rod Set
The valve rod set is shown assembled above. At the top left corner is the lifting link. Attached to it the long rod going to the right from that link is the radius bar. The radius bar connects to the top of the combination lever which goes downwards passing through the valve stem where it is also connected. The valve stem goes to the right side in the photo. The downward pointing combination lever connects to the union link at it's bottom end. The union link connects back to the left to the crosshead cover. One thing to note is that the long radius bar has two pins built in towards the left side. Those pins will sit in the curved slot of the expansion link already installed on the locomotive model. In the prototype and the model, the radius bar slides up or down in the expansion link depending on the position of the lifting link and lifting lever to which it attaches.
Engineer Side Valve Rod Set Installed
The above photo shows the set of valve rods installed. In order to install the radius rod the expansion link was disassembled along with the link mount. A number of small screws hold everything in place so that the rods may be disassembled, adjusted and if necessary replaced.
Set of Lifting Lever, Reverse Lever, Reverse Shaft and Mounts
Reversing Lever Assembly Mounted on Locomotive Model
The white ABS lifting link at the bottom left of the photo attaches to the fireman side lifting lever. That lever is on the end of the reversing shaft. The shaft passes through the mount bracket that is attached in turn to the expansion link brackets below the shaft end. Small 00-90 screws hold the brackets in place on the expansion link brackets. The shaft then passes across the engine frame underneath the boiler to the engineer side at the top of the photo. Just before that end of the shaft another bracket supports the shaft and is mounted on the engineer side expansion link brackets in the same manner as on the fireman side at the bottom center of the photo, The L shaped combination lifting and reversing lever is attached on the engineer side. At a later point in the model construction the engineer side reversing lever will attach to the reach rod that on the prototype is operated by the engineer to set the proper position for the lifting levers.
Model with Completed Valve and Reversing Gear Installed
The model features fully working motions of the various drive and valve rods along with the reversing gear. The model now has all of the motion gear installed. It all works fairly smoothly even though this is a static model. This feature allows one to demonstrate the fully working motion gear for interested visitors.
The next phase of the project will be to build the boiler assembly. This will be done in segments as the overall boiler is much too large to print at one time. The author contemplates printing the boiler in four round sections and the firebox. The cab will be a separate assembly. Details such as the smokestack, domes, walkways, grab irons and many other small details will be done separately and glued or screwed in place. The assembled boiler will be removable with a screw down the smokestack and another somewhere in the rear attaching to the cylinder and frame assemblies.
