I wasn't sure what to do about adding couplings within the 4 SUB unit. The motor coach, using the Hornby 2 BIL chassis, already had NEM pockets; a rigidly attached one at the driving end and a swivelling one at the trailing end. I have a few of the NEM pockets, as marketed by Bachmann and Hornby, so thought I would experiment a bit with these.

I filed a gap in the resin bogie ends and superglued the pockets in. I wasn't too worried about exact distances as I was going to experiment with different couplings to start with.

As it was, I started with Hornby tension lock couplings but these held the coaches too far apart. Similarly with the Hornby close-couplers. The 2 BIL rigid couplings were too short, as well as being less practical for handling a four-car unit. Kadees seemed like the way to go. I have settled on combinations of #17 and #20 couplings to get reasonable coach spacing while allowing for my tight-ish curves.

Once I have settled everything properly, I'll reinforce the pocket-bogie joints and cut off the dropper arms from the Kadees within the unit (no need for automatic uncoupling in a permanently formed EMU!).

Edit to add video link and additional info:

The NEM pockets superglued into the small recesses in the bogie frames seem to be a success, using Kadee #17 and # 20 couplings. I'll strengthen the joints with Araldite later.

The reason I had to use the odd mix of Kadee sizes was because I needed to keep the coupler heads clear of the headstocks, and each type of coach has slightly different overhangs from the bogies.

Here is a short video of the unit running temporarily as a three-car 3 SUB.

http://vid98.photobucket.com/albums/l265/jslynn/Rail/3SUB%20test_zpssxckqxrl.mp4