Sprat & Winkle couplings
Shunter George "Bulldog" Mullins critically eyes stock fitted with Sprat & Winkle couplings.
His shunter's pole is legendary among shunters for being rather crude!
The following notes on Sprat & Winkle couplings seemed to generate some interest when first posted over on gwr.org.uk, so perhaps they are of of use to someone here also. I have taken the opportunity to take some new and better photos for illustration.
Although the latest RTR offerings have helped enhance the looks of the RTR tension-lock coupling considerably, I still find them a bit too bulky and not quite reliable. They also do not offer the opportunity of "delayed action" uncoupling, which allows you to propel stock forward after uncoupling.
Looking for an alternative, I have taken to the fairly well-known Sprat & Winkle coupling, which - although a compromise in some respects - has proved quite reliable and fairly easy to fit. I find the delayed-action feature of these couplings simple and effective, and a plus for me is that they allow cosmetic 3-links to be retained.
Hook and bar. It could be argued that it is no less obtrusive than the modern tension-lock coupling. But I find it less bulky and with more functionality.
One hook operation
The Sprat & Winkle couplings are available in 2,3,4 and 7mm scale versions. As I model in 4mm my choice was between either the standard 4mm version or the "finescale" version. The latter is in fact intended for 3mm modellers but works fine for 4mm (including OO), as long as your curves are not too severe ( ie less than 4' radius according to MSE). This is fortunate because the standard version is a bit on the large side for my liking, and so I have opted for the finescale/3mm version.
In fact, even the finescale version is a bit more prominent than I would personally have wished for, especially when uncoupled. To minimize the visual impact I therefore fit a coupling hook to one end only, adding just the loop at the other end. This obviously requires stock to be facing in a particular direction when placed on the track, but on my layouts (and I think many others) this isn't really a problem. The absence of a coupling at one end also facilitates the fitting process (since you only have to fit one hook per wagon) and means I can add a prototypical (but cosmetic) coupling hook here instead, enhancing appearances a bit.
Coupled up using the "one-hook" approach
Mounting the couplings
The coupling hook features a square "paddle" at one end, which works as a counterweight beneath the wagon or coach body. The MSE website has an instruction sheet for fitting the couplings, and details on various extra parts not described here (including custom-made mounting plates). The instructions suggest two possible ways of mounting the hook: An "Upper" method in which the coupling hook is inserted through the headstocks (ie the "buffer beam" of the wagon), and a "Lower" method in which the hook rests immediately below the headstocks, hinged to the wagon floor with wire bent to the shape of a paper staple.
It is necessary to standardize on one of these two methods, and in principle I prefer the latter, which also comes recommended in the instructions: This requires only minor modification to the wagon or coach body, and is also - in my opinion - rather less fiddly. That said, I have made two minor modifications to this approach:
* Firstly, I replace the curled-up wire included in the pack with straight brass wire from Alan Gibson. I find that this makes it far easier to craft the wire-staple needed for fitting the paddle. The staple is then fitted to a section of square plastic rod mounted on the wagon floor. The plastic rod is not always necessary - it depends on the distance between the floor and the lower edge of the headstocks.
* Secondly, I find that the "Lower" method of mounting the coupling can sometimes give problems in ensuring that the coupling hook is fully horisontal: Exactly because it is underhung, the hook may come to rest at a slight upward angle against the bar of the loop on some wagons, which is neither aesthetically pleasing nor good for operation. I don't think it's just me, as I have heard others mention this issue also. My solution is rather crude I suppose, but effective: I simply open out a slight slot in the wagon just above the coupling hook, thereby allowing it to move freely to a full horisontal position against the loop. This may not be to everyone's taste, but the slot is really quite unnoticeable and can always be padded over with a filler if the coupling is removed.
The "Paddle", anchored with a wire "staple" to a supporting section of plastic rod
Uncoupling is by means of magnets located beneath the track, nested into the track base. The magnets attract the 3-links, thus tilting the hook downwards. When moving back up, the hook comes to rest in a position which allows the wagon to be propelled forward and left where you want it in the siding. Hence the "delayed-action" concept. The following photos illustrate the four main steps of this process:
1. Wagons are propelled in fully coupled condition
2. Coupling hook drops down as it is attracted by a magnet beneath the tracks
3. As wagons are propelled forward the coupling hook moves back up, but does not fully engage the bar
4. The uncoupled wagon is left where desired, and the rest of train is drawn backwards
For me this works well, with one important modification: Because I use only one coupling hook, the very powerful magnets occasionally uncouple the stock even when they are not supposed to - ie when the stock is passing slowly by. This happens even with a good layer of ballast above the magnets, and attempts with a sliver of Plastikard above the magnet doesn't help much either.
Again, I resort to cave-man technology for the solution: I simply break the magnets in half, thereby reducing the overall magnetic field. I say "break" because cutting will get you nowhere with these magnets - they need to be broken in two by holding the magnet with one pair of pliers and breaking downwards with another pair. Crude stuff, but it works.
Finally, I should perhaps emphasize that I have no affiliation with the manufacturers, and that these are the experiments of a novice: I do not have experience with the other non-RTR types of couplings available.