Tension lock coupling is very common in model railroad rolling stock for the simple fact that the vast majority of locomotives, wagons, trucks and carriages come equipped with a tension lock coupling of one type or another.
The simple tension lock is easy enough to understand - each coupling has a little hinged hook that pops up and over the bar of the coupling on the opposite number. In this way, each coupling links to the other in a secure fashion.
Before exploring the world of delayed action (or delay action) tension lock uncoupling, it's worth taking a quick refresher in standard manual and semi-automated tension lock uncoupling techniques.
Tension Lock Manual Uncoupling
The trouble is that when it comes to separating the rolling stock, a manual approach must be taken. The little hooks need to be lifted up, at the same time, and the locomotive driven away to separate it from the rake.
Many model railway enthusiasts have come up with a variety of ingenious hooks and bars that can be used to decouple the tension locks, but most of them require some kind of unprototypical intervention.
Model railway manufacturers have also added their own solutions - usually taking the shape of decoupling ramps or between the rails devices to aid uncoupling in a semi-automated way.
Tension Lock Auto-Uncoupling
For many, though this isn't enough. Automating the tension lock uncoupling process has become a preoccupation of many model railroad operators.
For example, Brian Kirby (see Brian Kirby Uncoupler Variations) has developed a fairly sophisticated do-it-yourself magnetic decoupling solution, that can be enhanced using movable and electro- magnets.
This technique requires that non-metallic (or at least, non-magnetic) tension lock couplers are used, ruling out the many owners of Hornby rolling stock. Even there, though there is a solution (see How do I Convert Old Hornby Couplings to New Type) but it requires changing the couplings themselves.
If you're going to do that, some might argue, why not go the whole way to fully automated, delayed action tension lock uncoupling solutions?
Delayed or Delay Action Tension Lock Uncoupling
Delayed action (or sometimes delay action) tension lock uncoupling is a way of automating the uncoupling process such that the uncoupling doesn't actually take place until the direction of the rake is reversed, allowing the loco to separate.
Imagine an Inglenook switching puzzle. With regular uncoupling, some kind of uncoupling device has to be placed at each fork so that trucks (wagons, or carriages) can be spotted on any one of the sidings.
As the article Inglenook Kadee Magnet Placement Advice points out, delayed action uncoupling allows a single uncoupling device to be placed at the throat of the Inglenook, and rolling stock spotted in any of the sidings.
To achieve all of this, the most common solution is to use something called a knuckle coupling. The most popular manufacturer is Kadee (see the blog post on adding Kadee couplings to rolling stock.)
There are other solutions, which we will examine in future posts. On a personal note, I have used Kadee and the Brian Kirby alternative, and have found that both have their uses, with a slight preference to the simplicity (and cheapness!) of the Kirby magnet uncoupling solution.
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