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Working Instanter Couplings

Working Instanter Couplings

Working Instanter Couplings – OO Scale

One of our customers & good friend Dave paid a visit this week, one of the things that he showed & demonstrated was his MRG HAA coal hopper upgrade project. Dave is currently building up & super detailing a couple of full MGR wagon consists. He’s using the older Hornby/Railroad MGR hoppers as a cost-effective way to build up the consists. In the process, Dave is adding super detailed parts & also upgrading the wheelsets. The buffers are being changed & bufferbeam pipework added using Lanarkshire Models super detailing parts.

Now the focus of this article is the working scale couplings. Dave has cut & removed the Hornby Tension Lock couplings from the wagons. He’s fitting scale working Instanter couplings which are made by Smiths. The kit comes as a set of parts to be assembled by the modeller & also pre-assembled which cost around 50 pence more. Dave saves go for the pre-assembled one as the kit of parts version can be fiddly to assemble. The kit in question is the Smiths LP6F Fine Instanter Couplings Assembled Brass (Pack of 8) for OO Gauge. The drawhook is spring mounted which allows the couplings to open up more to negotiate tighter radius curves.

They can be a little fiddly to couple up, but Dave says the best way is to angle the wagon downwards at around 45 degrees. This makes the coupling hang clear of the buffers, then its a case of carefully dropping the chain link over the draw hook. Another method is to use a rod type tool, which will help lift the chain link over the draw hook.


We found that curves of under 3rd radius caused the wagons to buffer lock & derail. The wagons are fitted with non sprung buffers, so we think that wagons with sprung buffers using these couplings should get around 2nd radius curves. This I’ll test out on some of my own wagons with these couplings & report back to the club to let you know how I get on. The couplings as per the real thing can be set to close or further apart by depending on which way you set the instanter. If using tighter radius curves it may be worth fitting a Kadee coupling on the leading wagon & loco to prevent them buffer locking.

Overall during the test run for this article, the couplings performed well around the layout, which includes an incline various crossovers Reverse curves etc. As you can see in the video clip, they look fantastic in use. Though on the loco we had to fit an improvised hook to prevent buffer lock between the leading wagon & loco.



Installing the couplings

First, remove the molded drawbar hook, & drill a suitably sized hole to take the long bar part of the drawbar hook.

Next, insert the long bar of drawbar hook into the hole. The drawbar hook should be able to move back & forth within the drilled out hole.

Now feed the spring over the long bar end on the drawbar hook. Insert the small rod section through the end hole on the bar. Glue or solder the bar to the rod to prevent it from falling it out.

The rod will act as the stopper for the drawbar hook, the drawbar hook should be able to slide back & forth without falling out. In the image on the right shows how the installation looks after fitting.

Now repeat fitting the couplings to the other end of the wagon as well as your other wagons & locos. As you can see in the photo, it shows the couplings in use. The instanter allows the wagons to coupled closer or further apart as per the real thing.


Further improvements to the Hornby Railroad & 1st tooled Hornby HAA coal hoppers.

Another modification that Dave has done is to fix the swivel axle mounts. Hornby designed these wagons to run around 1st radius curves, so the axle mounts have a degree of movement. Dave has removed the axle mount from the wagon & cut off the pivot. Then glued the axle mounts back into place. This has improved the running quality of the wagon. The wheels are also in process of being upgraded to finer scale type.

In the photo on the right can be seen the wagon dissembled back down to the chassis frame. The swivel axle mount pulled out from the pivot hole.

The pivot has been cut off & filed flush. Here you are looking at the underside of the axle mount in this photo. Also, note that the tension lock coupling has also been removed from the axle mount.


The axle mount is then glued back onto chassis. Care is taken to make sure that it sits true & straight to give trouble-free running.


Other upgrades are also carried out, these being cutting the plastic buffers off & replacing with white metal correct size & type buffers. The bufferbeam has further improvement added in the way of the brake pipes. Again this is a white metal part. These are then all painted up.


That’s it job done!! A vast improvement & simple upgrade to the Hornby HAA coal hopper wagon.


Many thanks for Dave’s assistance & photos. You can see more of Dave’s layout here:

Happy modelling

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