here are some photos from the beginning how the coupling is put together

the first picture depicts the upper row of 4 contacts, one the right hand side are 2 pins for the symmetrical coupling, pin 1 is than connected via a wire with pin 4 and pin 2 and three are also connected together with pin 3 showing the 2nd symmetrical connection

the 2nd and 3rd picture shows the plug with already one pin connector and on the back are 2 pins soldered together which forms the coupling shaft peg.
4th picture, are male pins which I use for connecting pin 1 + 4 on the lower row and use them for the coupling shaft peg and also for the connecting pins. for the upper pin 5 + 8 I use a different wire as it needs to be longer and I form this to hold the coupling shaft into place which you can see this on the previous pictures.

the plug sleeves themselves aren't fixed solid enough into the plug, so the extra solder when pushing them back into the slot stay there permanently and don't fall out or get pushed backwards. the outer 2 plug sleeves I add a drop of superglue to hold them into place.

the second picture also shows a raised border which I've shaved off, this allows the coupling shaft to go a bit deeper into the plug and thous reduces the distance between carriages, in future I also intend to shorten the coupling shaft to shave off the front of it so the carriage is completely together but one has to be careful when going around curves there is no interference with any other part.

I'm looking into it how can I reduce the length of the connecting pins without influencing the strength for both plugs to stay together under pressure

John

Nice!
It wasnt until the second-last photo in your third posting, that I realized you were doing 8-pole couplers. You should state that from the beginning, as it makes the whole thing much more interresting! (Even though I now see that you indicate it somewhere in the text, in your second posting...)