I am sure these questions have been asked a hundred times before, but having spent some time using the search facility, I am none the wiser.
I have recently returned to the hobby, my last (unfinished) layout was dismantled and sold off then I moved back to the UK from Finland. Seven years later, the bug has bitten again and I am accumulating various bits and pieces for a simple 4 ft shunting layout in OO.
My problem is the couplings - I have a Heljen 1370 GWR pannier tank engine, various old second hand Bachman wagons, and my latest acquisition, a GWR brake van from Oxford Rail. The Bachman wagons all have the old style big ugly couplings, but they do couple together easily, which is a plus. The Heljen and Oxford rail stock have small tension locks couplings in NEM sockets.
I had assumed that with NEM being a standard, these wold be the same, but I cannot couple the engine to the brake van as despite both being modern NEM couplings, they are at different heights. There is a step in the loco's coupling, whereas the van has a straight coupling. The couplings are not interchangeable as the 'tails' that fits into the NEM pockets are of different lengths (7.4mm for the loco and 4.9mm for the brake van - both as close as my eyes can manage with a standard vernier calliper - my electronic one needs a new battery!). I have spent several hours today trying to find a set of standards for 4mm NEM sockets, and though I found plenty that gave height above the rails, none offered any idea of a standard length for the tails or sockets.
I would like to standardise on couplings so that all the rolling stock is interchangeable, but have no idea which is standard. I have been thinking of using Kadee rulings as they seem well-liked, but not sure where to start, despite have waded through a dozen or more pages here.
My previous layout used Spratt & Winkle couplings, and I still have a few etched brass sheets of the hooks & counterbalance, but they are are fiddly to fit to the wagons, etc. - I remember cutting all sort of extraneous material off my locos and wagons before. I would prefer a simple and reliable coupling that will work on all my current and unknown future rilling stock - any suggestions?
I am including a picture of the NEM couplings from the brake van and loco.