< Rear Pony Truck 1 >
Rear pony truck has front and back frames combined by axleboxes. I prepared one casting for the two frames. The center beam of the casting is only for reinforcement of cast pattern.
The photo shows all of materials for the axlebox assy. I divided axlebox in two castings, so as to ease casting. Also I separated the flange from the oil pod, as a laser cut plate.
I started with inner axlebox. In four-jaw, front and back faces are finished parallel. Then the center hole for axle bush is finished truly square.
The outer axlebox is finished in the same way.
Inner and outer axlebox are clamped together. Whole job is chucked in a vise. Then starting hole for tapping is drilled. And step hole to sink bolt head is cut by an end mill. After that, only the inner (upper) part is removed.
Screw hole is tapped in the outer (lower) part. Other screw holes are opened here. All of coordinates are controlled by X-Y table.
Top face of the assembled axleboxes is finished by end mill.
The bush is made from gunmetal rod. Inner and outer diameters of the bush are finished. Then two bushes are parted off one after another.
The photo shows how to align the large frame casting onto the narrow miller's table. In advance, two rules are fixed truly square on the table. Pivot pin of the frame touches an edge of the vertical rule. Thus the pivot center's X-coordinate is transferred to the horizontal rule. Then the bolting faces for axlebox can be aligned equal from the center. After that the bolting faces are finished by end mill. Incidentally, the frame is clamped in three positions with three packing. These three points determine datum surface of the job.
Axleboxes are separated again. Then the outer axleboxes are aligned onto the frame. I used a rule again to determine Y-coordinate.
The frame is drilled through the axleboxes.
The frame is sawn and separated to front and back parts. Re-assembled axleboxes are bolted onto the frames. Note two roll pins align the drilled holes truly. The bushes are not glued yet.
With suitable round rod, two bushes are centered and glued into the axleboxes. I used Loctite 603 to glue them.
Push rods and brackets for 'side control' are put on the back frame. Bolting faces of both the bracket and the frame is trued up. The push-rods are made in the same way as the eye bolts of the equalizer.
Gunmetal bush for the pivot pin hole is glued. Bush is not vital for pivot pin but I wanted to omit spacing washers which make assembling troublesome. The bush hole diameter is 5 % larger than the pivot pin, so as to allow the rear pony truck to tilt in any direction.
Prototype C53 is semi matte black finish, same as the William. For the William, I painted stove enamel and baked. But enormous C53 is not easy to bake with a tiny infrared heater. I searched substitute and some engineers advised me to use polyurethane enamel paint prepared for automobile, which is as hard as stove enamel and heat-resistant for painting smokebox.
First I tried liquid type and disappointed. In every time for paint, I will be bothered to mix pigments, flat base, hardener and thinner at defined percentages. I don't have spray gun and compressor to begin with. Next I tried aerosol type that has inside container for hardener. Before use, you push its nozzle hard, then the inside container is broken and the hardener is mixed with other elements. It is much easier to use but you have to use up a canister within 24 hours after mixture. After all I decided to use the aerosol type, because I found suitable semi matte black in its color variation.
The photo shows test piece of the paint. The left half is stove enamel for William, and the right half is polyurethane enamel. Both of them are semi-matte finish but the urethane's black color comes out very well.
The bogie truck wheels were already painted with stove enamel. For re-painting, I have to remove the wheels from the axles. I employed 'gear puller' for this operation, with heating back side of the wheel by propane torch. After that I removed stove enamel by suitable thinner and painted polyurethane enamel together with the rear pony truck wheels.