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This is about making an operational link and pin coupler system. I know there are commercial versions available. But having been a "minority gauger" I know how supplies dry up. This is not a finescale two pins and a link system but a system to make "OPERATIONAL" link and pins. Don't E-mail about your ability to use a three piece system in Nn3, etc.. I have used a three piece system and it doesn't work operationally. When the car is 18 inches away and at an angle the three piece doesn't work. I replace the pin and links with a u-pin. I have used this idea in smaller scales and have had great success with way freight switching.
I use an un-prototypical u-pin to form the coupling. It is un-obtrusive at the "three foot rule" and makes switching possible on a real world layout.

The drawbar heads can not be made to use the three piece system of two pins and a  link. The problem with the prototype is alignment going in and out of 18" radius curves. The head mis-alignment becomes a big factor.
(Click images to enlarge)
Our drawbar compared to a PSC drawbar from their long loco pilot. On the left is the Mark 2 version.
ABS or Styrene plastic ,040 and .090 thick is used. I like ABS because it files cleaner. The .090 is cut 3/16 wide. The .040 is cut 5/32 wide strip. The .090 forms the shank.
Make a jig to cut the coupler pocket from the Bachmann car.
The plate allows an even cut. My plate is an old car weight that is 1/16 thick. The plate was shimmed to get the right amount to be taken off the pocket. I added .030.
The pocket should be the height of the drawbar shank, the early drawbar shown.
Gut the pocket. The two areas at the arrow should be the same height.
Reduce the shank behind the head 5/32 from the front so that the drawbar slides into the frame.
The drawbar shank should just slip into the Bachmann frame.
Glue the drawbar into the frame and add a plate on the bottom. The head should be about 1/32 away from the frame. Brush some MEK or liquid plastic cement on the coupler to remove the filing fuzz.  Paint the coupler roof brown.
I make my u-pins from standard staples from Staples. They are 3/16 from pin to pin for my 18" radius curves. Make one pin longer than the other. The long pin goes in first.
The best tweezer is this 12" long device with the tip ground. Make sure the tweezer is non-magnetic or the pins will hang on it like a booger.
This system is not for everyone but it works for me. It allows for switching operations on a layout set in an era before knuckle couplers. A car can be equipped in about a half hour.
We are basing our drawbar on this one from the The Car Builder's Dictionary (1888)
(Click to Enlarge)
Click here for a scale drawing in PDF format
Reduce the neck behind the head to 3/32. Cut a .040 piece 1/4 long and glue the .040 face onto the drawbar.
Square the face up on the .090 piece. Cut a 5/8 long piece.
Drill a #55 hole through the drawbar with the hole edge 1/32 back from the face.
Mark and center punch at the center of the face.
#50 drill into the drawbar until the drill passes the #55 hole. Elongate the hole by twirling the drill at an angle.
The elongated slot is centered on the face.
Bevel the edge, I used this cutter. It can be beveled with a hobby knife.
Sculpt the drawbar with files
Prototype drawbars from the The Car Builder's Dictionary (1888)
(Click images to Enlarge)
Link and Pins from EZ-Mates
Click here to make Link and Pin Drawbars from EZ-Mates