Delayed (or Delay) Action Tension Lock Uncoupling Solutions

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.

Brian Kirby Uncoupler Variations

Over the years, a fair amount has been written about the legendary Brian Kirby Uncoupler. For those who aren't familiar with it; it's a way of cheaply modifying the tension lock coupling found on Bachmann stock so that it can be uncoupled using a magnet.


Essentially, it revolves around gluing staples to the tails of the individual couplers so that they can be flicked up and down as the staple is attracted downwards, forcing up the tension lock.


(There are some links at the end of this piece to help you visualize that a bit better!)


However, there are a few things that can be done to improve this clever idea, and while it cannot be made to replicate the action of delayed decoupling products such as those from Kadee, they can be made to behave a bit more naturally.


Electro-Magnetic Variation


The first is easy - use an electromagnet that can be switched on and off to decouple the stock at will. This prevents mistakenly running over the magnet slowly, and decoupling the stock unintentionally.


The trouble with this is that you need an awful lot of electromagnets to have enough decoupling points to make it worthwhile...


Sliding Plate Variation


...unless you mount them on sliding plates. These can slide in one of two ways - up and down, rather than using an electromagnet, or forwards and backwards. For those familiar with wire-in-tube point changing, this idea won't be that novel.


The magnet is mounted on a plate which can then be slid backwards and forwards under the layout (or in a special groove cut into the baseboard) thereby allowing decoupling under multiple lines.


There are bound to be combinations of these that can be used together to make even more variations, but with these basic techniques, operators can finally wave goodbye to the 'big hand from the sky'!


Brian Kirby Uncoupler Links


The original 'Magnetic Uncoupling for Bachmann Couplings' post on the Model Rail Forum web site.


A YouTube Video of the Kirby Uncoupler in action.

Model Railroad Uncoupler Magnet Placement

There are two ways to achieve semi-automatic uncoupling. The first, as discussed in Delayed Action Tension Lock Uncoupling, allows for the locomotive to uncouple by simply changing direction, having passed over a magnet.


However, converting to Kadee style couplings can be expensive, and is not without it's own issues - see Adding Symoba NEM Pockets & Kadee Couplings. 


The alternative is based on a variation of the Brian Kirby magnetic uncoupling solution. This is a cheap, do-it-yourself addition to couplings that use a plastic tension locking hook (rather than the metallic Hornby ones) and allows for 'instant' uncoupling when positioned over a magnet.


Uncoupler Magnet Placement


In both cases, the placement of a magnet under the layout (or at least embedded in the base board) causes the decoupling to occur. The placement of the magnet tends to be fairly permanent, and as such needs careful thought.


For example, when delayed uncoupling is used, a rake can be spotted on any one of a number of sidings, even after passing over sets of points. But, when using immediate uncoupling, a magnet is needed for each individual siding.


This is explained more fully in the Kadee Inglenook Magnet Placement Advice article.


Another important consideration is for those who are planning an oval layout : every time the train runs over the magnet, the uncoupling action will take place. Depending on the rest of the track plan, this may, or may not, matter.


As a matter of course, though, it is usual not to place magnets underneath ovals, and reserve them for terminus operations (fiddle yard, terminus station, goods yard, etc.)


When Placement Doesn't Matter


In the Variations article, for those who haven't read it, there is at least one solution to the above - use an electromagnet. These can be switched on and off at will, and as such are widely used for selective immediate automatic semi-magnetic decoupling.


A final thought - there's often no need to put modified coupling in place on each piece of rolling stock. Commonly, though, they'll be fitted to locos and brake vans, as well as the start and end wagons in longer rakes.


However you choose to implement it on your layout, magnetic uncoupling can open a whole model rail experience!

Inglenook Kadee Magnet Placement Advice

Many of us, especially those of us with a shelf switching layout, have an Inglenook. Kadee magnet auto-coupling/decoupling makes operating an Inglenook much easier (when it works) but is a real pain when it doesn't, or if the magnets are put in the wrong place.


First off, what exactly is an Inglenook? Figure 1 shows the basic layout (adapted, with many thanks, from the Model Railways Shunting Puzzle Web Site) and can be adapted to any scale, with a couple of points (switches) and 7 or so bits of track.

Figure 1: Basic Inglenook

The operating fun to be had with the Inglenook relies on being able to pull wagons off trains (rakes) which are parked on the ends of the Inglenook, and swapping them with others, in a kind of Towers of Hanoi style puzzle.


While decoupling using the paintbrush-with-a-loop-of-wire-on-the-end solution is all well and good, for the ultimate in operating action, many enthusiasts like to implement some kind of automatic decoupling solution. Kadee manufacture such a solution, using magnets and knuckle couplers to provide a reliable shunting experience.


Due to the way that they work, on an Inglebook, Kadee magnet based auto-decouplers  are a great solution for one simple reason : delayed decoupling. For layouts using electromagnetic decoupling (in my opinion, the next best thing to Kadee's solution), magnets are needed at each place where a wagon (truck) can be uncoupled.


Wagons can be uncoupled  from other wagons, or from the loco (shunter), and Figure 2 shows where the placements should be (or could be) for an Inglenook using only electromagnetic automatic decoupling.

Figure 2: Inglenook Magnet Placement

There are other places that magnets might be appropriate or desirable, but Figure 2 serves to illustrate the point - 3 separate magnets, with three separate buttons, are required to be able to spot trucks (wagons) on each of the three sidings of the Inglenook. 


Kadee magnet based uncoupling changes this, as seen in Figure 3.

Figure 3: Inglenook Kadee Magnet Placement

The reason only a single magnet is required is that once decoupling has been activated the remaining rake (train, or wagon) can be shunted into place, and remains decoupled. When the loco pulls away, the decoupled wagon or rake is left in place - delayed decoupling.


There is a drawback, however. In order to decouple a relatively long rake, the track in front (to the left of) the magnet needs to be long enough to accommodate it. However, if this proves to be a problem, more magnets can be added on the sidings themselves, this allowing decoupling with some, or most, of the train over the points.