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Tweedale - Thin Wire Tension-Lock Couplings


awoodford

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The standard tension lock couplings in use on Tweedale have been an ongoing source of irritation. They work reliably enough, but they are just so darned ugly. The original plan was to replace them with Alex Jacksons, but that has now changed and I've decided to stick with tension locks but make my own from from thin wire. They seem a bit less fiddly to set up than the AJs and the tolerances are more forgiving. I'm very pleased with the results, so I thought I'd share the details below on how they were made and fitted.

 

I've been using Roger Nicholls 'Yorkshire Kadee' uncoupling system (see the 'Operation' blog), and for that I only needed a hook at one end of a wagon and a loop at the other. The uncoupling system is beautifully simple, but has its limitations and only really works on trains being pushed in one direction. As most of the sidings on the layout face the same way this is fine. However on the sidings at Dale End, which face the opposite direction, wagons had to be uncoupled manually. One unexpected bonus with the new couplings is that they are so fine and light that, with a bit of care, it is now possible to automatically uncouple wagons in the other direction as well.

 


Here's a wagon to be converted, a Hornby box van.

Tweedale14-1.jpg.9de2e49d9cb7d63e8d8e32a9f1e21caa.jpg

 

The van body was unclipped from the chassis to make things easier to work on. The old couplings were unclipped, and the associated mounts removed with a hacksaw and craft knife, to leave a flat base beneath the floor for the new couplings.

Tweedale14-2.jpg.e17a29b594028d4272f0bf08b77edd88.jpg

 

The sketch below (not to scale) shows the critical dimensions for the new couplings.

 

Dimension A needs to be a bit less than than the minimum buffer length, so that the hook doesn't hit the buffer beam of the next wagon in a train. The buffer lengths on my stock are around 5-6mm, so I set this dimension to 4mm.

 

Dimension B depends on the minimum track radius of curves. The sharper the curves the furthur the loop needs to protrude beyond the buffers. For the 18 inch radius curves on Tweedale I found 3mm to be suitable for this dimension, and allows coupling and uncoupling on the curves.

 

Dimension C, the width of the loop, depends on the severity of reverse curves in the trackwork. There are a couple of nasty ones on the layout (added to my list of things to avoid in the future) so a wide loop of 14mm was used.

 

The coupling height was set to 10mm above the track, higher than standard tension locks, but it means the fittings under the floor are less visible.

Tweedale14-3.jpg.169f9de152f40e99198574b42bb0d3e9.jpg

 

The old steel wire that I'd used for AJs in the past had turned brittle over the years and just broke when trying to bend it, so I used 0.3mm diameter nickel silver tramway overhead wire instead (I happened to have some in the spares box). The hook was was made by first bending the wire at right angles 4mm from the end, then bending it back on itself. It was then gripped in pliers 2mm from the end, and the long tail was bent 45 degrees. The tail was bent at right angles for the striker at 15mm from the point of the hook, and cut off 9mm from the bend.

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A small piece of brass rod (not sure of the diameter, but it's a loose fit in a 1mm hole) was soldered in the right angle bend of the hook wire. Any burrs were filed from the ends of the rod. The mount for this pivot rod was made from plasticard and Evergreen styrene strip, into which 1mm holes had been drilled. For the loop end, wire was bent to shape and soldered to a piece of copper clad sleeper strip.

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The wagon was pushed up to a 10mm height gauge (made from plasticard) to determine how much packing, if any, would be needed for the coupling assemblies. This wagon didn't need any. And yes, that chassis really is bowed, its not just the photo!

Tweedale14-6.jpg.43e42774faa6fb23c79b9827d48a1975.jpg

 

The loop and hook assemblies were glued in place with UHU. Scraps of paper marked with dimensions A and B (mentioned above) were used to set the final positions. A piece of plasticard (X on the photo) was glued behind the striker to hold the hook at the correct height.

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The glue was allowed to set overnight, then the couplings rechecked against the height gauge. Any final tweaks could be done by bending the wires slightly.

Tweedale14-8.jpg.7bcd44e48e1d71bec98a14c13397a821.jpg

 

Cheers, Alan.

Edited by awoodford
Restored lost images

  • Like 5
  • Craftsmanship/clever 1

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A neat solution made to look deceptively easy to produce by someone with the skills to do so.

 

If the plastic parts of tension lock couplings were made of clear plastic, they would be less obtrusive. Just the hooks would be very obvious. 

 

Ed

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Guest Simon Dunkley

Posted

A neat solution made to look deceptively easy to produce by someone with the skills to do so.

Talk about damning with faint praise...

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It's a very good solution. People with good skill levels often produce items that I think I might be able to copy. Then reality comes to mind. I might be able to do this but I doubt it would be such a neat job. Tweedale is a good idea well produced by a fine modeller.

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Guest Simon Dunkley

Posted

It's a very good solution. People with good skill levels often produce items that I think I might be able to copy. Then reality comes to mind. I might be able to do this but I doubt it would be such a neat job. Tweedale is a good idea well produced by a fine modeller.

Nothing like giving up before you have started...

No one is born with the ability to put a 90 degree bend into a piece of wire without a bit of practice. https://ewjr.org/2015/01/03/honest-choices/

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edp2, Simon Dunkley, thanks for your comments. I wouldn't say there was a lot of skill required here, more patience and a methodical approach. Only basic modelling tools were used, a junior hacksaw, craft knife, pliers, wire cutters, a 1mm drill, a small file for deburring. The soldering was not absolutely necessary - Araldite could have been used instead. As I had a dozen wagons to convert, the various bits were cut, bent, drilled and filed in batches, to produce kits of parts that could be put together fairly easily once the old couplings had been hacked out. And at the end of the process, if it was not quite right, a bit of judicious bending generally cured any problems.

Alan.

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