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Train Couplers


A coupling (or a coupler) is a mechanism for connecting rolling stock in a train.

In the real world, the design of the coupler is standardized, and is almost as important as the track gauge, since flexibility and convenience are maximized if all rolling stock can be coupled together.

The equipment that connects the couplings to the rolling stock is known as the draft gear.    (Source: Wikipedia)



Okay…so your train has left the freight yard, you’ve traveled over 100 compressed miles, and now here you are ready to deliver a carload of upholstery to a furniture factory.
..You’re backing into the spur and your “crew” is getting ready to uncouple the freight car so it can be left at the warehouse and unloaded. What happens next?

..the Worst case scenario

Two giant hands come down from the sky and try to jiggle the freight car loose from the rest of the train..
It doesn’t come loose right away so the hands have to lift the car off the track in order to unhook it, then these hands try to re-rail it again next to the furniture factory.

..second Worst case scenario

One giant hand holding a big stick comes down from the sky and puts the stick down between the cars, between the train couplers; the big stick turns a little and the car rolls free..

..the Best case scenario

There are no hands in the sky.
The train backs up into the spur and stops for a moment.
The couplers separate, and the train pulls forward a little, then backs up slowly, pushing the car into position next to the unloading dock.
The train pulls forward with the spotted car remaining in place at the loading dock.
The train then pulls out onto the mainline to travel to its next destination.

now doesn’t this scenario sound more idealistic?


Commercially Available Options:

It is important to realize that real-world coupling systems comprise of mechanical, pneumatic, hydraulic, electric and electronic components, which makes modelling and manufacturing of these components quite difficult. Model train manufacturers improvised and developed numerous coupling systems and mechanisms that allow for practical train operation, albeit they don’t always look or operate prototypical.

While most trains will happily run on the same tracks with each other, there can be problems when you try to couple them to each other.


Examples of Couplings:
L-R: Hornby tension-lock coupling; European (Lima) style coupling; USA horn hook (or X2F) coupling; Kadee compatible knuckle coupler

Tension-Lock Couplers

The tension-lock coupler was popularized by Hornby.
The type is common to most scale models made for the UK market and it appears on almost all Hornby trains, Bachmann Branchline models and the Lima UK models.

They are a unrealistic looking device, but they do work effectively (when not knocked around too much) and simple to use.

They use a sprung ramp for uncoupling. When under tension (no slack in couplers) they will not uncouple, but when tension is slackened (by stopping the train and reversing the locomotive) they easily uncouple over the ramp.

It’s is more difficult to remove a carriage without using an un-coupler.


European Couplers (Lima)

The European coupler is more commonly known as a Lima coupler, although again, it is in use by many other companies.

Most early prototype models were supplied with the Lima couplers, who introduced the couplers in the early 70’s.
When properly adjusted these couplers operate quite well.
Unfortunately in practice, many operators found these couplers to usually be more difficult to use with shunting trains.


USA Coupler / Horn hook couplers

The USA coupler is also known as the X2F or Horn hook.

Until recently, the majority of USA prototype trains had these fitted, and they are still very common.

They are simple and cheap to produce. It’s just a pity they don’t always work all that well.
They are generally mounted on the bogie and rely on side pressure to stay coupled.

Unfortunately, this side pressure can cause derailments, especially when reversing.

They don’t look anything like the prototype train couplers and rely on side pressure to hold them together, which is a major problem when backing up, because the side pressure often causes derailment.


KADEE Coupler

The Kadee type coupler has mostly replaced the X2F on the better quality US trains and is the preferred coupler of many hobbyists.

Micro Trains is now the trade mark holder of the Kadee coupler.

Although there are now a number of manufacturers, the type is often called ‘Kadee’ as this company had manufactured (and invented) it.

In recent years other companies have started to supply their own versions, and as such, models are now sold with them already fitted.
(One example of this is the E-Z mate manufactured by Bachmann)

Kadee couplers are now manufactured and available in a variety of options ranging from plastic to machined types.

The main advantages of the type is that it looks like the real thing and can be uncoupled magnetically.

These couplings look like the auto couplers on many full size trains. And they make use of magnets to uncouple them.

They also feature delayed uncoupling that enables a modeller to uncouple a wagon over the magnet, and then push it to the desired location and leave it there without recoupling. Wagons can be removed by simply picking them up. Not possible with most other coupler types.



Rapido Couplers

In general Rapido couplers are fine reliable couplers, but they look like boxes and they are difficult to uncouple automatically.

That’s why serious N scalers began to convert their cars and locomotives to Kaydee/Microtrains couplers years ago, and why major American producers such as Atlas and Walthers have switched to a magnetic type coupler which is similar to the Microtrains coupler.

Kato still supplies a Rapido-style coupler today, although it is slightly different to the original Rapido design.


In N scale, the majority of models come with a plastic “block” coupler known as a Rapido coupler, introduced by Arnold in the early 1960’s.

The Rapido coupler rapidly became the standard of N scale around the world.

Read this Article that provides an overview of common N-Scale Couplers

The only serious alternatives to the Rapido is a range of couplers by Micro-trains and Con-Cor, and more recently the European NEM couplers.
(These are similar in operation to the Kadee type and are preferred by many modellers)

t4a_coupler_concorLeft: Con-Cor “Rigid Jaw” Coupler and Right: Micro Trains

Knuckle couplers

These are more prototypical, they look better, and they work well with the magnetic uncouplers. Also, you don’t have as many derailments when the trains are backing up. Kadee makes most of these for HO, Hon3 and larger scales, but other manufacturers like Atlas, Kato and Athearn are making them as well. Micro-Trains Line (MTL) and McHenry make knuckle couplers for smaller scales.

Some people like to put Z scale knuckle couplers on the fronts of N scale locos (or N scale couplers on the fronts of HO locos) because the smaller train couplers look more realistic on the larger models. The same idea can apply to the backs of cabooses (cabeese?).





 Other Couplers

There are also other kinds of couplers, but these are either older types now obsolete or new ones purchased separately and fitted by the modeller. European modellers for example have quite a number of old and new choices regarding couplers.

These couplings are used by some European manufacturers, and like Kadee types, they also feature delayed uncoupling and the ability to remove a wagon from a train simply by picking it up.


2.  Compatibility

Being able to couple any number of trains from different manufacturers remains an issue, and the resolve seems to be for the modeller to decide on his own preference, and then to convert incompatible couplers.

The easiest thing for the newcomer to the hobby to do is to stick to the trains of one country.

If you do end up with a mixture, you can either have a train of each type or make up a wagon with a different coupler at each end.

couplinga2The above photo shows another problem many people encounter, especially if restarting the hobby using an old set they’ve had for some years. Both the wagons above are by the same manufacturer – Bachmann. The one on the left is an earlier product from the 1980’s. The one on the right is an improved version from the 90’s. The different couplings are the most noticeable thing and obviously prevent the two from being coupled together. Other differences are the improved free-rolling metal wheels and lowered body of the later model. The old one sits higher and has plastic wheels.


3.  Conversion

Most people don’t like horn hook couplers and can’t wait to replace them with (or “convert” them to) knuckle couplers that are more realistic and work well with the magnetic uncouplers.

This takes a certain amount of time and effort to convert all of your equipment to knuckle couplers, which is why people usually do this in a stepwise fashion, converting locomotives and cars one at a time, sometimes mixing them in consists till they are all converted.

You can have several conversion cars on which you have a horn hook or Rapido (in N scale) coupler on one end and a knuckle coupler on the other so that you can connect both types within your consist.

One option is to do the rear of one loco and the front of the lead car first, so that it becomes easy to uncouple the loco from the rest of the train.

For N scale, the couplers are usually mounted in the trucks, and are rather difficult to replace without learning new expletives in your vocabulary. It’s easier just to replace the whole truck assembly (made by MTL).

Coupler height

No matter what kind of train couplers you have, they won’t work well if they are mounted at the wrong height. You will need a coupler height gauge for your scale to tell whether your couplers are the right height or not. You can get one from the NMRA or from Kadee, or even (HO only)…HO Coupler Height Gauge

Assuming the couplers are mounted on the cars, if the coupler is sitting too high, you can lower it by putting a shim between the bottom of the car floor and the coupler pocket. If the coupler is too low, you can add one or more washers between the truck and the car bottom. If the coupler is mounted on the truck, you may have to replace the truck assembly or the wheels, particularly if the coupler is too low.


4.  Magnetic uncouplers

Kadee was the first manufacturer to develop this system, in which a special magnet (not just any magnet) is positioned under the track at a strategic location like in front of a branch line, spur or ladder, such that, when a train is backed up and stopped with the knuckle coupler over the magnet, the “glad-hands” of the coupler come apart when slack is allowed.

The train should then be pulled forward a little, and then backed up again to push the car into the proper position without recoupling. The train can then pull out of the spur leaving the car where it was placed.

This is called the “delayed uncoupler”, as opposed to the “regular uncoupler” which will recouple itself to the train after it is pushed back off the magnet.

Electric uncouplers

These are also available from Kadee for all scales, which are primarily electromagnets activated by applying current to a wire wrapped around a cylinder many times which creates a magnetic field. These have to be mounted in a space cut out from under the track, which is really no problem if you’ve used foam for your subroadbed.



Uncoupler installation tips

  • If you are going to use uncoupling devices, it makes sense to include them in your original track planning.
  • It’s easier to install them as you are laying your track initially rather than trying to do it later, although it can still be done.
  • You may have to use a rotary tool or track saw to cut out and replace small sections of track in order to place the magnets, but it wouldn’t be that difficult.
  • If your track is already laid and you want to install un-couplers, go for it. You’ll be glad you did.


5.  Discussion & Personal Preferences


The following overlay shows the outlines of popular couplers.


  • It is clear that their sizes aren’t as varied as they appear
  • McHenry coupler is the bulkiest – and that makes it look quite out of scale.



Profile View:

Profile views allow us to view the couplers from both sides.

General Note:

  • Accumate seems a bit lower profile than the rest.
  • McHenry has excellent detail on one side, but unfortunately the  spring on the other side looks unrealistic.



Quality of molding of the “gear boxes” and coupler parts:










  • Images show that MT couplers have very crisply molded and flash-free parts. That is especially evident in the MT’s draft gear box.
  • Kato coupler parts are just as crisp as MT
  • Accumate’s molded edges are bit softer and surfaces are a bit rougher than MT or Kato
  • McHenry’s draft gear box has lots of soft details and rounded edges.
  • MT molded a nifty draft gear box cover latch into the screw sleeve. It works quite well.
  • McHenry attempted a similar latch but the molding has soft edges and it doesn’t latch the draft gear cover at all.
  • I’m surprised that in this day of modelers looking for couplers which are close to true scale size McHenry would manufacture such oversized looking couplers.

Notes in the Centering springs.

  • This is a bit difficult to evaluate without an uncoupling magnet but I can feel the spring tension with my finger so I can make an observation.
  • Some people don’t really care about magnetic uncoupling because they manually uncouple their cars using some sort of mechanical uncoupling tool (like a wooden skewer).
  • But some layouts have industrial spurs out of reach and magnetic uncoupling is vital to enjoyable operation.
  • Nothing is more frustrating than time wasted on unsuccessfully trying to magnetically uncouple a car while the fast clock is running!
  • Many modellers have expressed that in their experience, MT couplers are the best ones to use when using magnetic uncoupling. This is especially true when they are lubricated with powdered graphite. I suspect that this is due to their well molded parts and the very soft copper-alloy springs.
  • Kato couplers have a similar spring but it’s a lot stiffer, and it is pretty much impossible to perform automatic magnetic uncoupling using Kato couplers.
  • Accumate uses plastic leaf centering springs molded to the coupler shank, and those are much stiffer than the MT springs and thus they do not reliably uncouple over a magnet.
  • McHenry also uses plastic leaf springs molded to the coupler shank but those are only used for centering the shank, and for unlocking the knuckle they use a method very similar to the one used in Kadee H0 couplers.
  • Unlike other N scale knuckle couplers where the coupler is split horizontally for a scissor-like opening action, McHenry pivots the knuckle itself. It is pivoted on the uncoupling pin and held closed by a small steel spring. That spring seems a bit stiff to me for an uncoupling magnet to reliably open it. That in combination with the stiffer plastic shank-centering spring doesn’t seem to me like it will uncouple reliably over a magnet.


  • This evaluation shows that the Kato couplers seem to be closest in shape and size to the 1:1 AAR couplers.
  • McHenry’s shape is somewhat reminiscent of the 1:1 coupler but it is too chunky and its body is way too long.
  • MT coupler is oversize but not as much as McHenry, however its overall shape is not very similar to 1:1 coupler.
  • Accumate to looks most toy-like. Its shape is just plain strange. Lots of flat surfaces joined at odd angles.

Not included in this evaluation may be numerous other couplers that may or may not be available to the author.

Please note that the author has a strong bias towards Micro-Trains couplers, for reasons that include:

  • MT couplers have the best quality molding (especially their couplers with reverse draft angle) and in my experience they seem most reliable.
  • Reliability is linked to the clean molding, close tolerances and the soft springs they use
  • MT currently has the largest assortment of coupler conversions of all the knuckle-coupler manufacturers
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