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!