Barspin (Thingiverse) built a SW1500 locomotive but it was missing the couplers
Here you go...
3d Solutech PLA
I set the coupler on it's base in Cura and added supports
I set the knuckle standing up and used support
Carefully trim the support off. Leave the stubs on the hinges, but clean around them.
On the Knuckles, only the bottom should have a slight amount of support to trim.
I use straight pins to act as the pins for the knuckles. Take your time putting the two pieces together. It helps to have the knuckle facing slightly out to get the pin in.
Hope you enjoy.
I placed a shim under the rear to get a good fit on the locomotive
Created in Fusion 360 using a drawing I found on the internet. Then I scaled the part. It took three print iterations to get it to a finished assembly.