A set of parts forming the trailing truck equalization linkage is shown above. The trailing truck equalization consists of a cross bar at the end of the locomotive Back driver springs and two down links that will ultimately connect to the trailing truck equalization levers.
Above is shown the location and arrangement of the trailing truck equalization crossbar and down links. The back portion of the chassis will be attached in pockets located on the insides of the main chassis frames.
The pilot-cylinder frame section (PCS) is shown above with the raft and supports still in place. This section required 6hr and 48min to build. The large flat portion at the bottom is the front platform under the smoke box door of the locomotive and over the pilot truck.
A slight rounding of the bottom edge of the platform occurred due to the tendency of the ABS to disconnect from the support material when the length exceeds 100mm. The outer edges lifted as the printing went forward and resulted in a swept back look for what will become the front edge of the platform. This edge will connect to the front sill of the locomotive that will have the cow catcher and front coupler attached. It may be feasible to adjust the sill design to work with the swept back edge. If not, a new run will be needed to build the platform and front frames.
The frame parts mate well with the main chassis frame sufficiently snug that the front platform is lined up well with the main frame.
The gap between the platform and main chassis will eventually have the cylinder assembly attached. The cylinder assembly is nearly as wide as the platform and fills the gap with the piston and valve cylinders. The front ends of the Front driver springs have the cross bar and single down link that will eventually connect to the pilot truck equalization lever. That lever will have a pivot point mounted on the bottom of the cylinder assembly in the center of the gap.
The cylinder assembly fits between two features on the frames that keep the cylinder assembly in place. The cylinder assembly may be bolted or glued in place depending on the need for access to the pilot truck equalization system.
Due to a prediction of over 31 hr to make the back frame with the main cross pieces in place, the side frames were made separately. They are 7.5" tall nearly at the extreme limit of capability of the BFB-3000 printer. During the printing the beams would move a bit with the extrusion head due to friction causing irregular edges and widths near the top of the printed parts. The overall run time was 4hr 55min. Very little raft and support material is located only at the bottom region so each frame stands alone. This allowed them to flex side to side mainly with the extrusion head forces. If they are to built again, a sacrificial internal support frame will be included in the design to stiffen the frames and prevent much motion during printing. The sacrificial frames would then be removed by cutting, grinding and sanding.
The two main cross pieces of the back frame are the rear spacer-draw bar pin and tender tensioner shown at the bottom right of the photo and the trailing truck pivot spacer and boiler mount shown at top center. Each of these took 5+ hrs to build and included a considerable amount of support material that needed removal.
After removal of support material and clean up the four major pieces of the rear frame are shown above. The pieces will be glued together with support jigging before the assembly is attached to the rear chassis pockets.
The rear frame was temporarily held together with rubber bands and slipped into the chassis pockets to check for fit and alignment. The back frame is a bit loose in the pockets probably due to filing to smooth the back frames which had been built with quite a bit of roughness due to flexing while being printed. A portion of the ABS driver gauging tool was used to support the back frame for the photo.
The front frame front edge curvature is noticeable in this view. More than likely this part will need to be built in smaller parts and assembled to avoid this effect.
The overall size of the locomotive frame is seen in the above photo against a ruler. The 23" length is for the locomotive alone, the tender will be a separate assembly and will likely be about 12" or more in length
The back frame assembly has a large void in the middle extending from near the front edge to about the right end of the green ABS tool used to support the assembly. That region will eventually have the clinker chute that extends down from the firebox to doors used to empty clinkers and ash from the firebox on the prototype. Several other parts will be located on the back frame. These include the equalizer bar pivot mounts, trailing truck spring mount front mounts, trailing truck spring rear attachment frame, and rear firebox mount. Also located attached to the frame underneath the rear firebox mount will be the trailing truck centering spring assembly.
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