Installing Kadees on Atlas 89 ft flat car
Here is a step-by-step on installing Kadee couplers on Atlas 89 flat cars, including modifying the draft gear box and draw bar to increase the side-to-side movement. With this modification, these cars can operate on curves as tight as 36 inch radius (072) without easements. Doing these modifications makes it possible to model modern railroading in a home layout setting.
Step 1: I began with an Atlas two rail car, which comes with an under car scale mounting pad. I removed the Atlas stock couplers and set them aside. At one time these pads were available from Atlas's parts department, but they have been out of stock for a while. If you don't have the Atlas part, you can fabricate your own from sheet styrene and install it using 2 X 4mm screws. You can see the pad in the photo further down the page.
Step 2: Using a rotary tool I cut away the sides of the Kadee draft gear box in order to increase the range of side-to-side motion.
Step 3: On the bottom of the coupler itself is a tab that fits down in the floor of the draft gear box. To increase the side swing, you need to file off the sides of this tab as shown below. To better illustrate this step, only the right side was filed off in the photo:
Step 4: Assemble the Kadee coupler, and install in the mounting pad. The mounting holes on the Atlas part are off for Kadee installation, but using 2mm screws, there's enough play to make it work. If making your own pad, simply use the Kadee draft gear box lid as a template to drill holes. I mounted the Kadees with 2 by 8 and 2 by 10 screws and 2 mm nuts
Step 5: Intall the mounting pad to the car. If you making your own pad, 2 mm screws will work. My best recollection from the last time I made my own pads was that 4 mm is the correct length for mounting the pad to the car. Every car I've seen, whether finished for 2 or 3 rail has the holes for mounting the coupler pad already tapped:
Step 6: The modified draft gear box obviously is not prototypical. To correct for that, I install flexible "false" sides that will move out of the way as the coupler moves hard right or left. I make them out of this handy Pactra trim tape I bought in a hobby shop many years ago. I just cut to length and stick it in place. One also could use electrical tape or very thin sheet styrene glued (expoxy may be best) to the remaining wall of the gear box:
Here is the finished product. Check with a height gauge and if necessary, add Micromark shims to lower the coupler to the correct height:
With the modifications to the draft gear box and the coupler, the car now is 36 inch radius (072 capable).