HO Scale Model Railroad Couplers

By Roger Heid and Ulrich Albrecht

In this blog, we will try to shed some light into couplers and the associated issues, primarily for HO Scale models. Let us reach as far back as the early 1950s in Germany. During those years, Fleischmann ruled in the HO 2- rail DC world, Maerklin was, and still is, the only manufacturer representing the HO 3-rail AC world.

Right from the onset, they were competitors. If you got started with model railroading, you had to decide which one to go with. There was absolutely no out-of-the box compatibility between the two. This included the couplers. Maerklin had their trusty loop coupler, aka Relex coupler; Fleischmann featured their proven claw coupler, still does.

Maerklin Loop or Relex Coupler

Fleischmann Claw Coupler

On smaller locomotives, such as the BR 89, the couplers on both ends were mere hooks, called hook couplers.

Sample of a Hook Coupler

In the beginning, the way couplers were mounted to locomotives and rolling stock varied, depending on the individual models. Often couplers were not easily available as replacement parts. In some cases, a replacement required major surgery. This is now history.

In the late sixties, Maerklin started to introduce a new coupler assembly that could be replaced without any tools. On the bottom of the car is a slotted prong; the coupler assembly was pressed onto that prong or stud. Two springy, fork-like spikes provided the centering of the coupler, thus functioning as a guide mechanism. On some less expensive motive and 2-axle rolling stock models, this system is still employed.

Close Coupler Coversion for Motive Stock

Occasionally, especially after a replacement procedure, the couplers seem to be hanging too low. In most cases, this can be remedied by carefully forcing the two stud halves further apart, using a small screw driver blade. A close look at this affair will make this self-explanatory. Maerklin provides a coupler height gauge which comes in real handy, at times.

Coupler Height Gauge Maerklin 7001

About 15 years ago, Maerklin introduced the ‘Close Coupler’ to take the place of the ‘Loop Coupler’. The close coupler shortened the distance between individual cars, making the appearance of the train more real life like. For the above mentioned coupler mounting system, conversion couplers are available.

Conversion Couplers incl Uncoupling Tool

As far back as in 1979, the NEM coupler pocket started to show up progressively on more and more European made motive and rolling stock models. This made coupler related issues a lot easier to deal with. No matter what the coupler assembly consists of, there is always this box like pocket. These days, all European made motive and rolling stock comes with the Maerklin type loop or close couplers, by default, except Fleischmann. They still use their venerable claw coupler, but they provide other couplers as well.

Sample of a coupler inserted into NEM Pocket

Henceforth, any coupler type of one’s choice could be inserted or replaced. Not all couplers are created equal. Some of them can actually cause problems. In respect to this, I have the following to say:

Instead of losing a lot of sleep over these problems, I developed my own approach. First off, you need to ensure that all cars, including the locomotive, do not uncouple while whizzing around on your track layout. If this happens, you need to take a close look at the coupler mechanism. Some peening and tweaking will have to be done to ensure the couplers do their job.

Along the line, you may have a certain train consist where you never change the individual cars around. Staying coupled together is really the only issue here.

On the other hand, you may wish to employ shift yard techniques, like concocting freight trains of varying consists. There you like to just bump one car against the other, thus coupling them together.

Unfortunately, this does not always happen. If it does happen, however, some cars may disconnect while the train is in motion. This can be frustrating, especially when you are demonstrating your trains to a visitor. When you are by yourself, this is less prone to happen. But if some friend or relative watches, it is bound to happen, isn’t it?

Now you need to troubleshoot individual couplers. You may need to replace some couplers. For instance, I do not like the couplers Brawa rolling stock comes with. From my experience, they are flimsy and break easily. I automatically replace them with Roco universal couplers. I just love those.

Ulrich has this to say:

Over the years, I have tested various types of couplers and came to the following conclusions:

The coupler has to provide a solid, quite rigid connection between the cars for the short coupling mechanism to work.  However, couplers also have to allow for a small amount of flexibility so that the cars can compensate independently for small unevenesses in the track.  If the connection is too rigid, even a small imperfection in the rail causes the coupler to act as a kind of lever between the cars the action of which can cause derailments.  In my experience, the Roco Short coupler and the Fleischmann Profi-coupler are too rigid.  On the other hand, the standard NEM coupler and the Kadee are too flexible so that reliable push operations are not possible with cars having short coupler mechanisms.

Fleischmann Profi Coupler

The Marklin close coupler and the Roco universal coupler are ideal as far as rigidity and flexibility are concerned.  However, the Roco coupler couples on both sides and is quite flat.  This results in a firm, secure connection and no problems with the buffers.  The Marklin coupler engages only on one side, which leads to unwanted decouplings, and also is quite high.  Unless one has very large radii, the coupler interferes with the buffers.  Both of these couplers also connect to standard NEM couplers.  Here Marklin has a slight edge since the Roco coupler’s hook is open on one side.  On the other hand, the Roco coupler is available in a height adjustable version which works with a variety of connectors for Fleischmann and Roco rolling stock without NEM shaft.

Roco Universal Coupler

Roco Height Adjustable Coupler

In summary, the Roco universal coupler is by far the best coupler in my experience.  I have a few Marklin couplers left.  I usually remove the Marklin metal hook, and use the coupler at the front of steam locos like the 55 which I use in both directions.  Being black, it is kind of unobtrusive without its metal hardware.

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In addition, there are also the ‘Current Conducting Couplers’. They allow you to supply electricity from car to car needing only on pickup shoe. If every passenger car of a fairly long train has a pickup shoe mounted on the underside, the resulting drag factor could prevent the locomotive from being able to pull the train. The installation of these is best left up to the experienced modeler.

Maerklin Current Conducting Coupler

Maerklin Solid Draw Bar Kit

Roco 4 pole Conductive Coupler

Then comes an issue regarding the Maerklin Telex Uncoupler. There is the older style that goes way back to the analog days. I have two locos equipped so. This older Telex coupler works quite well with loop, close and Roco universal couplers. Unfortunately, they seem to have gone out of production.

The metal plate behind the hook lifts up freeing the loop

The new type I take with a grain of salt, to put it mildly. The mechanism is quite feeble and unreliable. If left turned on too long, the little coil inside may get fried, leaving the coupler useless. I have four locomotives that came with these new Telex couplers. On one of them, the couplers work well with the close couplers and the Roco universals. Loop couplers need to be precisely adjusted, most of the time. On the second loco, only the rear coupler works consistently; the front coupler either needs to be prodded or it decides to take the day off, possibly depending on the moon phase. On the other two locos, well, I decided to forfeit the feature, and I removed them. Roco Universals took their place. I do employ two Uncoupler Tracks. They always do the job, without fail.

These couplers can be repaired in some rare cases, but don’t hold your breath. Replacements should be done by a very advanced modeler or a technician.

Maerklin Kof with Telex Couplers

This blog is probably not covering every aspect of the coupler world and may not answer all the questions you may still have. But it is a good start to get to the bottom of some of the problems one encounters.

If you have something to add on, please, leave a comment. If you have questions, please post them in the Forum under the appropriate topic.

Thank you.