Boxcar Underframe

Underframe for an HO scale 40-foot boxcar. Designed to fit an Athearn boxcar, but should be adaptable to other manufacturers. The bolster boss on the underframe of one of my cars mushroomed (could not fit washers to set the coupler height) and the frame seemed to generally be in marginal condition, so I designed this to replace it.

The frame and other pieces can be used as-is, or combined with 0.025 in diameter phosphor bronze jewelry wire representing the air lines and brake rigging.

Modeled based on these sources: 1 and 2

As noted elsewhere the original Athearn underframe is "backwards," something I've tried to fix.

The jewelry wire is a bit too big to be true to scale, but it's what I had on hand and working with smaller wire would likely be too much of a challenge for me.

The brake detail components were bonded to the underframe with model cement. The two halves of the train line were soldered together. The line from the AB valve to the train line was also soldered.

The designs of the various components include features to facilitate incorporating the wire (e.g. the underframe includes slots for the two halves of the train line to be rotated into position and there a holes in the brake cylinder, AB valve, and air resevoir).

If I were to do this again, I'd:

• Modify how the AB value is connected to the train line in order increase the clearance between that line and the rod connecting the floating lever to its truck.
• Slightly increase the height of the bolster posts so that the truck mounting screw bottoms out on it rather than on the truck itself (though this clearance can be tricky if the car needs to be shimmed to set the coupler height.

Two different versions of the underframe are provided. Version 6 is the same as version 5, except that the draft gear box geometry has been slightly improved. Version 5 is provided as that's the one I've taken all the way to completion.