Couplings

Micro-trains supply an extensive range of conversions to add couplings to N gauge rolling stock. Sadly none are specific to UK models. Luckily, they are sufficiently similar that the same conversion kits can be used. The no. 1129 kit converts a Rapido coupler pocket with a "medium" length shank coupler. This seems to be OK for the bogie oil tankers and reduces the coupled distance slightly (to 8.3mm buffer to buffer).

Remove the bogie from the model. It is held in by a plastic pin that simply prises out. Remove the existing coupling and its spring. Using a scalpel through the turns of the spring can help keep it from flying out. To get the height right (mine are lower than standard) I needed to cut away the bottom of the pocket (marked). The sides of the opening at the front need to be chamfered using a knife. The Micro-Trains leaflet illustrates this.
Open the coupling packet, being careful with the content. There are four items: a small sprue with the coupler itself, a small spring, the iron wire and a cast metal insert. The insert will stop the coupling from moving vertically, but leaving it free to move side to side. Cut out the two parts of the coupling from the sprue, and clean all flash off the metal insert. Its inside surface must be smooth.
Assembler the coupler shank, following the diagrams in the kit. Make sure you get the iron wire on the bottom of the coupling! The second part of the shank assembles over the wire, and the two parts need to be handled as a pair using tweezers.
Insert the metal insert into the bogie's pocket, and using tweezers put the spring inside it. Buying spare springs is good insurance! For the coupler height I use it will need to be almost flush to the bottom of the bogie and must be level.
The tricky part: lift the insert, and using tweezers inser the coupler shank into it. I find it easiest to be looking into the bottom of the coupling pocket. Get the shank the right way up!
Use a small blob of epoxy to secure the metal insert into the bogie pocket. You will need some clever arrangement to set the coupling height for this operation. After the glue has set, check the height of the coupling. Mine shown here is a little too low.
Adjust the iron wire so that it just grazes a 10 thou shim placed on the rails. Bend to adjust; be careful not to damage the shank. Trim the excess wire at the top.
Here is the finished product! Check that it moves freely from side to side, and returns to the centre. Check its height is OK so that it doesn't foul on buffers etc (this is why I'm using a lower height standard).