EMD F7 in SCALE
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THE F-UNIT GETS NEW TRUCKS: Part VII, cont'd
Continuing with the brake rigging, I found it advantageous to assemble the inboard and outboard brake shoe hangers to the trunnions (the links that join the bottom ends of the hangers), since that is where most of the fiddly stuff is located. The below illustration was my working drawing, courtesy of Dave Newell.
I deviated slightly from the assembly drawing, in that I reversed the screws holding everything together so the nuts were facing outward. Doing so gave me much-needed clearance around the roller chains, which are very close to the brake rigging.
Below are some pictures of the truck—still inverted—with the brake rigging installed.
Below are some close-ups of some of the brake shoes, taken after the truck had been righted and placed back on the erecting stand.
After installing the brake rigging, the next procedure was to assemble and mount the brake cylinders, which are Precision Steel Car (PSC) parts. The end caps are attached to the cylinder body with 2-56 hex-head brass screws and nuts. Handling dinky parts like that is not something I can do very well, so I got some help in putting the cylinders together. I completed the cylinder assembly with linkage parts also sold by PSC. All parts were primed with an etching primer to assure a solid bond, followed by multiple coats of gloss black. I gave the paint three days to fully harden before handling the cylinders.
Assembling and painting the cylinders was one thing. Attaching them to the truck frames was another. This proved to be quite a challenge due to minimal working clearances and the size of the fasteners. The screws I had gotten with the trucks for mounting the cylinders were 2-56 × 1/8 inch hex heads, which proved to be impossible to use, one reason being the screw holes in the cylinders' mounting feet are partially obscured by the cylinder's body, preventing the use of a nut driver. Even with a miniature open-end wrench and a lot of patience, I could not get the screws started into the tapped holes on the truck frame.
Assessing the situation, I concluded the mounting screws were not long enough—only two threads protruded through the mounting feet, not quite enough to pick up the threads in the tapped mounting holes in the truck frame. Unfortunately, the next length available in a hex-head was 1/4 inch, which I determined would be too long for the depth of the mounting holes. I needed screws that were 3/16 inch long, but could not find a source that had them in hex head.
The solution to the problem was to use 2-56 × 3/16 inch socket-head capscrews, with split lock washers to take up a little length and to avoid having the screw head in direct contact with the cylinder's relatively-soft brass foot. While socket screws are not to prototype, they made it possible to complete the assembly.
The screws and washers I obtained are black-passivated, stainless steel, which are relatively unobtrusive. I was able to start and tighten these screws with a ball-end hex driver, although I was glad I had more screws than needed to mount all cylinders, as one or two found their way to the floor—naturally, never to be seen again.
Mounting the cylinders was a laborious process, requiring several hours to complete both trucks.
Below is a photo of one of the cylinders after being mounted on a truck.
Continued in the next post...