Couplings

Tension-lock couplings cause problems:

In order to get over these problems, and for other reasons, I decided to fit my stock with Kadee couplings.

Bachmann 4-wheel wagons

With these wagons, you just pull the tension-lock couplings out of the NEM coupler pockets, and replace them with Kadee No.17 couplers. These couplings are very short, resulting in a 1mm gap between the buffers, but they will work with the curves on my layout. No.19 and No.20 couplers are too long, resulting in a large gap between the wagons. The No.18 couplers reduce the gap between couplings in tension from 8mm to 5mm and in compression from 5mm to 2mm, and does not prevent the stock going around first or second radius curves if you really must use them.

The NEM coupler pocket is too high, so I have stuck a little bit of 40 thou plastic to the top of the pocket to bring the Kadees to the correct height.

Other 4-wheel wagons

I generally use Kadee No.5 couplers on other 4-wheel wagons, mounted such that they protrude a couple of millimetres in front of the buffers. The top of the coupler mounting box is level with the bottom of the buffer beam. I have had no trouble with couplers mounted this way, but there is no guarantee that stock with couplers mounted like this will go round first or second radius curves.

Sometimes, mounting these couplers means that you have to drill holes through the wagon weighting strip. Do not be frightened of this, but calculate the correct position for each hole and drill it and tap it 8 BA, then fix the coupler with an 8 BA bolt.

Modern Bachmann bogie stock

For modern Bachmann designs, changing the couplings is easy. You just pull out the old couplings from the NEM coupler pocket, and replace them with Kadee No.19 or No.20 couplers. However, there are some problems with this, as Bachmann’s NEM pockets are not at a uniform height, so the replacement couplers may not be at the height recommended by Kadee.

Bachmann Bogie with Kadee coupling There are two types of bogie used on Bachmann Mk.Is. One has a hole 5 mm. from the cut-out to clear the coupling apparatus, the other one doesn’t. For a bogie with the hole, you cut off the raised boss on top of the bogie, and file it flat. For the other type of bogie you drill a 1.8 mm. hole, 5 mm. from the cutout, on the centre-line of the bogie. In both cases tap the hole 8 BA. Next, take the coupling apparatus, and cut off the lug that fits into the body to operate the close coupling feature. Cut off the deformed circle, leaving a fair amount of plastic — it will resemble a letter Y with short curved top arms and a long upright. Insert a Kadee No. 20 into the NEM pocket, and mark a point 30 mm. from the end of the Kadee. There is a circle marked on the plastic, and this point should be somewhere inside this circle if you have measured it correctly. Drill this 2.2 mm. (8 BA clearance). Place the coupling holder on top of the bogie and pass through an 8 BA countersunk head screw (cheesehead is no good, because the head is too tall). Screw this up tightly; you may wish to put a nut on the end of it. When you are satisfied that all is OK you might want to glue the coupling holder to the bogie.

If you just replace the tension lock couplings in Bachmann Mark 1 coaches with Kadees you should be aware that, with long heavy trains, the close-coupling mechanism causes the coaches at the front of the train to derail. This is because the spring is not strong enough to hold the coupling mechanism against the weight of the train behind, and the couplings are forced to one side or the other by the shape of the cutout in the carriage floors. I’m not sure what happens in these circumstances with tension-lock couplings, but with Kadees I get derailments as mentioned. If I fix the Kadees to the bogies, these problems go away.

Other bogie stock

I decided that I had to do something about the couplings on my coaches, and I wanted to find a better way of mounting Kadees than on the bogies, which I normally find very troublesome. Couplings on the prototype are not mounted on the bogies (except for a few locomotives) but are mounted on the bodies. Also, it is common practice on American stock to mount the couplers on the bodies. So I decided that I would try to mount a couple of couplings on one end of the bodies of two of my Lima coaches, for a trial, and see what happened.

First of all, I pulled the bogies off the carriages. Then I removed all traces of the tension lock coupling from the bogies, cutting them so that both ends were identical. The plastic is very easy to cut: I used a Stanley knife.

Next I cut three 28 x 8 mm. pieces of 30 thou plastic sheet for each coupling. These were fixed on top of each other under the floor of the coach, hard up against the buffer beam. Some coaches have deeper buffer beams: these should be trimmed to the depth of these 3 bits of 30 thou. Then, positioning the coupling where it should be fixed, I drilled a hole small enough to take an 8 BA bolt through the three strips of plastic and through the floor of the coach. Don’t drill it clearance, and you may want to tap it (I didn’t need to). The coupling is a standard Kadee No.5, assembled as shown in Fig.1 of Kadee’s instructions. Attach it with an 8 BA bolt, and test it against Kadee’s height gauge. To my astonishment it was the right height first time! If you’ve done it right, you won’t need a nut on the other end of the bolt, so you do not need to take the roof off the coach. When you are satisfied, you can cement the coupling in place with your favourite liquid poly, in which case the bolt helps to take the weight (after all, you don’t want the coupling to come unstuck when you start your 16-coach train!).

Bachmann Queen Mary Brake Van

To mount Kadees on the Bachmann “Queen Mary” brake van, proceed as for the Lima coaches, mentioned above, with the following changes:

  1. Do not drill the hole for the bolt too far, or you’ll come through the platform! Use a washer, between the bolt-head and the coupling if your bolt is too long (mine are ¼ inch, which is too long). Kadee supply washers of various thicknesses with some of their couplings (not with No.5s though); these will fit on an 8 BA bolt.
  2. You will have to perform more surgery on the bogie. Not only do you have to cut off the tension-lock coupling, but you also have to cut off the stretcher, and the slightly diagonal bits that go back towards the axle, but only as far as the first cross-piece between the wheels. This gives more clearance — the bogie’s swing is limited by the wheels hitting the coupling’s draftgear box, but that doesn’t happen on Hornby second radius track, so you should be O.K.

Remember when screwing the bogie back on to the vehicle, not to screw it up too tight, or the bogie won’t be able to swing.

Tri-ang 0-4-0T Nellie, Polly and Connie, etc. Repainted Nellie with Kadee coupler

Remove the tension lock coupling. Drill an 8 BA clearance hole through a Kadee No.20, at the furthest point from the coupler where it is wide enough to take the hole without breaking because of how little plastic is left, then cut off the last 1/16″ or so of the coupler so it fits in the space available on the chassis. Fit it to the chassis by screwing a ¼″ 8 BA countersunk-head brass bolt into the hole for securing the tension-lock coupling that you just discarded. I found that the coupler tends to sag, so I cut the smallest sliver of 30 thou plastic card and inserted that as a shim between the tail of the coupler and the chassis, fixing it there with liquid poly, and lo and behold the coupler is the right height as shown by my coupler height gauge.


Copyright © 2000–2011 Jane Sullivan.