URS Assembly Instructions

Installing your N-Possible couplers is easy using the following instructions.

URS General Arrangement Diagram

Step by Step

Step 1: Plan and Prepare

Make sure you have all of the required parts and plan your installation.

For each coupler you should have a Coupler Knuckle Shank, Coupler Thumb Shank, Coupler Spring and Universal Retrofit Splitter.

Gather the tools you will need for the installation:

Fine grit diamond small file (nail file or emery board also works well)
Wooden Toothpick
Hobby Knife
Tweezers
Soft Pencil for lubrication (i.e. 6B, although standard HB pencil also works)
Rotary tool (Dremel) or other tool with fine burr bit (Dremel 108 or similar) or cutoff wheel for adjusting car frame (if required)

Remove the existing coupler from the box and test fit the n-possible coupler in the box. In many cases, the coupler will fit with adequate clearance with no box modifications required.

Step 2: Modify Coupler Box & Mount Shim

Make the required modifications to the coupler box. A rotary tool (Dremel) with a fine burr bit is ideal for easily milling plastic boxes while the cutoff wheel can be used in metal frames.

Inspect the splitter shim, and make sure it’s flat and that the spring splitting tab is aligned. Use tweezers to adjust, if necessary, it’s important that the shim is flat. Test fit the shim in the box. Typically, you want the shim on the top of the box, but it’s possible to mount the shim on the bottom as well.

Make sure the box top where you are mounting the shim is clear of any burrs and that the box is level. Assembly defects in model under frames and coupler boxes are common but coupler height and alignment is critical and a level box is imperative for reliable operation.

You MUST glue the shim into the box, since the splitter must be fixed. Use a thin layer of adhesive (our favorite is Bob Smith Industries IC 2000 “Tire Glue”) to ensure things remain level. Ensure that the shim is properly aligned with the splitter tab centered relative to the pivot post.

Step 3: Prepare and Assemble the Coupler Spring and Shanks

Lightly pass over the top of the knuckle shank and the bottom of the retainer shank pivot ring with a fine grit diamond file to remove any burrs.

Lubricate the knuckle shank around the pivot, the retainer ring and the knuckle face and retainer face with a soft (i.e. 6B) pencil.

Slide one end of the coupler spring over the “nub” at the back end of the Coupler Knuckle Shank. There is a slight boss on the end of the nub that should retain the spring.

Slide the other end of the coupler spring over the similar nub on the end of the Coupler Thumb Shank. It also has a slight boss to retain the spring.

The two shanks should now be joined by the spring.

Step 4: Install the Coupler in the Box

Install the assembled coupler in your coupler box making super sure that the coupler is centered with the spring split perfectly with the splitter tab.

Lift the coupler out of the box and adjust until you are positive that the coupler spring is properly centered on the shim. Even a single coil matters, so be precise and ensure the coupler is properly centering.

Re-assemble your coupler box. Make sure that the coupler is level, not binding, and is reliably opening and closing completely.

Installation Troubleshooting

If the coupler is binding, you can start with making sure you have not over tightened the box screws first.

If the coupler is still binding, you can reduce the coupler thickness by filing the coupler thinner. Factory boxes vary in height, so this adjustment in cases is necessary.

The retainer half has a raised ring portion by design. Start by slowly removing material from this section and re-testing. If you have removed the entire raised ring portion and the coupler is still binding, ensure that the shim is flush with the top of the box.

Consider filing the box lid too, but odds are if the coupler is still tight at this point you are dealing with a shim placement issue (the shim is not tight to the box top, glue thickness/unlevel placement).

If the coupler is not closing completely it is likely that it is binding. The other possibility is that the spring has too many coils over the retainer post, or the shim is placed too far back in the box.

Un-level couplers will lead to operating problems, specifically unreliable automatic coupling and splaying under buff. By design, they are tolerant to some amount of “un levelness” but that is best used for the inevitable variations in track work like grade transitions etc., and not on the base installation.

Troubleshooting “slop” in height and alignment often requires modifications to the car and or trucks. Common issues include under-gauge wheelsets, loose wheelsets in the truck and sloppy bolsters. You may be able to regauge narrow wheelsets but consider replacing wheels and trucks if the wheelsets are sloppy in the truck. You can also fill the needle bearing holes with some IC 2000/tire glue to tighten things up.

Loose bolsters can often be addresses by squishing the bolster pin in a vice to form an oval shape. Test bolster pins in truck to make sure they’re sufficiently tight/not too tight, and re-install the oval shaped bolster pins perpendicular to the length of the car.