I have two Bulleid brake third (BTK) coaches by Fleischmann to make my "period" passenger train as a BTK + BTK formation. This is not a prototypical formation for BR Southern Region operation, but I think it is plausible for Shelf Island, which needs lots of luggage space for airport passengers and additional emergency braking capacity for its 1:20 main line gradient.
These models (Fleischmann 5148) came supplied with Fleischmann "Profi" couplers fitted. I like the Profi coupler for coaches because it reduces the slop during changes of direction, but the factory arrangement sets the coaches with about 8 mm between buffer heads. This is the overall effect with a BCK (not used) and one of the BTKs:
Most of this post is to describe how I arranged for closer coupling, reducing the space between buffer heads by about 5 mm. The coaches still run on 18 inch curves, but they look a lot better on straight track. I have also added a Kadee coupler at one end (the set has to work push-pull at the moment) and some gentle weathering. I posted the description of the Kadee coupler before (19th January 2016), so I've put this at the end.
I used two Fleischmann 6574 couplers, one on each coach. I mounted the coupler heads as high as I could (just below the buffer heads) because this makes them look best - however, this makes them incompatible with couplers at the standard Fleischmann height, and you cannot use uncoupling ramps. Also, this conversion is irreversible. My conversion puts the 6574 couplers inside the coach, on top of the floor. If you try putting them under the floor they appear to fit but they foul the backs of the wheels.
This is what I did:
2. File off the moulded writing "Fleischmann" on the bottom of the new coupler housing to make a flat surface and glue the assembly onto the top of the chassis - I used super-glue reinforced with blobs of hot glue (I tried Mek-Pak but they fell off). Then cut a hole in the floor of the body to accept the coupler box and the full travel of the coupler, and cut a rebate out of the interior moulding so it fits down over the coupler box:
4. Put the coach body back together. Remove the original coupler from the bogie to go below the new coupler and cut off the coupler mounting. This is necessary to make a clearance for the bogie to swing. Fit the bogies back onto the model.
5. Fit the Profi coupler head onto its mount as high as possible, just low enough to clear the bottoms of the buffer heads.
Repeat this for the second coach, and try them out!
If you want to be able to couple up coaches on the track, you have to have some space between the buffers to let you compress the coupler heads and let them latch together. When I put my two coaches on the track, on a straight track, I found there was just enough free space to let me do do this. This leaves the buffers about 2 mm apart under compression, or 3 mm apart under tension. The coaches will propel around an 18 inch curve like this . . .
I don't have an airbrush and I'm pretty hopeless at painting so I paid someone to waft some frame dirt over the underframes, allowing it to go up onto the lower sides and a little higher at the ends. Then I picked out some highlights with acrylics and a brush. This photo is with the original couplers:
This is a Kadee #149 long under-set coupler in one of the #262 narrow gear boxes. The pin holding the original Fleischmann coupler pushes out with a jeweller's screwdriver, then I cut out enough of the bogie moulding to fit the gear box into the space above the existing coupling hole:
The bogie is moulded from a soft flexible plastic with a slightly soapy feel, so I used a M2 screw and a nut and washer to hold the box in place. The bolt passes through the original mounting hole, and the conversion is easy to reverse if the need arises.