A few steel hopper models have been progressing on my workbench. Each of them requires KD brake components. As I worked on these, I realized it’s been a while since a step-by-step illustration of the process has been published. This post will summarize the three methods I’m using on these models.
The K brake system was a common component of freight car air brakes. Two basic versions can be seen on many prototype photos. The KC version is easy to spot on boxcars as it looks like a one-piece element. It’s has the brake cylinder, air reservoir, and control valve combined as one unit. The KC hardware is also referred to as K connected.
Many freight cars don’t have the space to mount a KC brake system. Gondolas with drop doors and hoppers typically have KD systems. This is also known as K disconnected, or split-K. The brake cylinder is separate from the air reservoir and control valve in a KD system. An air line connects the two components.
I’m modifying HO scale Bowser GLa hoppers. AB brake system components are included with the kits, but these represent a later development. The AB brake system came into use in the early 1930s and became the standard for new and rebuilt freight cars through to the end of the steam era.
I model 1926, so I need to install KD brake components. Tichy offers an injection molded plastic set that I’m using to upgrade these models. The Tichy parts include a sprue of many brake system extras; levers, hand brake wheels, platforms, supports, and more. I’ll focus on just the KD brake cylinder and air reservoir castings.
After removing these from the sprue and cleaning part lines, the clevis on the brake cylinder is positioned vertically and needs to be rotated 90-degrees. I used a fresh single-edge razor blade to slice the piston and clevis near the end of the cylinder. I impressed a dimple into the center of the cylinder and used a #74 bit to drill a hole into the part. The piston has a larger diameter, so a #66 bit was used to enlarge the hole. The clevis and piston are inserted into the hole and a small amount of styrene cement was touched to the joint. Make sure the clevis is now mounted horizontally.
I installed a square 0.040-inch thick styrene pad on the underframe casting for the brake cylinder. You can see the adjusted position of the brake clevis in the photo above.
The air reservoir is mounted to metal bar stock on the prototype. File the narrow mounting area flat above the control valve. I used a strip of 1×4 styrene for the mounting piece. Use a long piece as it can be trimmed after it is installed.
There are three ways to proceed from this point with a range of tediousness. On the first car, I wanted to model the air line that connects at the rear of both parts. I used a #74 bit to drill holes in the back of the castings. A length of 0.020-inch wire was bent with about 3/4-inch between the bends. This was glued into the hole on each casting as seen in the above photo. Note the reservoir mounting strap was a bit long on this first try.
Before mounting the brake hardware as one unit on the underframe casting, the styrene strap on the reservoir needs to be angled downward. This is easy to do using your fingers and a little pressure. Test fit the unit to determine where the ends of the strap need to be angled outward to glue onto the underframe. When these final angles are set, the unit can be installed.
The brake cylinder was glued in place first then the reservoir straps are positioned and glued. Any excess can be easily trimmed away.
I ran into an issue when I test fit the frame on the car body. The air line can interfere with the truck screw mounting post. I sliced the reservoir mounting straps from the frame and used trip pin bending pliers to carefully bend the air line around the post. This will slightly change the reservoir location. Fortunately, the straps were long enough for the final attachment. I did not capture this moment of success with a photo.
On the next installation, I pondered how to make this easier. I crafted the wire with the bend around the truck screw mounting post and glued it directly onto the slope sheet support. I did not attach it to the brake parts.
The brake cylinder and reservoir were mounted separately, easing the installation process.
My mind kept thinking. We can see the line clearly in raw form but will it be visible at all in the murky shadows? If there are a few dozen hoppers to upgrade, would this detail be missed?
Moving along to the third car upgrade, I decided to eliminate the air line connection. The noticeable details are the different air reservoir and mounting strap. The photo above illustrates the results of the last two variations on the theme. I left the excess strap material so you can see how that can be used for final installation adjustments.
No matter which method you choose when adding KD brake system components to a hopper model, there will be tedious moments when you are adjusting the fiddly bits. I doubt I’ll ever install these exactly the same on each model, but at least the basics will be visible.
Work from prototype photos when you can. You will find subtle differences in how these components are installed.
USRA hoppers and copies of the design built in the 1920s had the brake cylinder mounted in a reverse position. Rather than the piston pointing to the end sill it is pointed toward the slope sheet. It is a subtle detail that offers a slightly different appearance to a hopper car end.
Of course, the Pennsy had their way of doing this, too. It seems the brake cylinder is mounted to the slope sheet in this image. I don’t think I’ll try this at home.
I’ll cover additional hopper details in an upcoming post, including the brake lever and pivot that is also visible under the slope sheet.
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