Model Electric Locomotives

Like their real sized counterparts, many models of electric locomotives can take their power from overhead catenary wires.  This is more commonly found with European model train manufacturers, from the very small (Z-Scale) to the larger garden railway trains from LGB (IIm-scale), but not every European manufacturer made their electric type model locomotives with the necessary internal wiring. Some manufacturers offered their own catenary system (Märklin, LGB), while others such as Minitrix and Arnold rapido relied upon other specialty catenary system manufacturers such as Sommerfeldt, Vollmer and Viessmann.

In the days before command control, energized model catenary systems allowed the model railroad operator to control two trains without complicated wiring.  As an alternative, powered model catenary let the model railroader control a train pulled by an electric locomotive while the powered rails illuminated the passenger cars.  In this way, the train would slow to a stop while the passenger cars remained lit, not possible if all ran from the same track power.

The Electrical Wiring

The general principal for all systems was the same, one locomotive was controlled by power from both rails while the second locomotive, an electric type, was powered by the overhead catenary wire with power returning via one of the rails:

In the above illustration, the steam locomotive (left), takes its power from both rails. The electric locomotive (right), takes its power from the overhead wire and returns it via the same rail as the steam locomotive.  It should be noted that both locomotives could be electric types, with one using both rails for power instead of the catenary wires.

This illustration uses the Minitrix color coding system; each manufacturer had their own color coding system. The color coding method is important since it helps simplify what can be a complicated installation. Likewise, the color coding system is useful when you are also using signals to start and stop trains, a common European practice.

The electrical connections are relatively simple: 

One transformer is connected to both rails of the track via a red and a blue connection. The second transformer makes its red connection to the overhead wires via a terminal mast; the blue connection is made to the same rail as the other transformer’s blue connection.

The Europeans often use individual signals to control trains by turning defined segments of track on and off.  The semaphores have internal circuitry for this purpose, while color lights use either a relay of special control button for the same purpose.  In both cases, (using the Minitrix color coding system), the blue rail is used to control a train’s movement.

Other manufacturers, such as Märklin, use the color codes of red and brown for the same purposes.

The Catenary System

Single Masts

The basic element of a model railroad catenary system is the single mast, which are used to suspend the electrified catenary wires:

In practice, many of the catenary systems actually have three individual masts.  One will usually be described as a “long” arm and the other will be described as a “short” arm (such as the one to the right). This is done so that the catenary wire will not always be directly over the center of the track below.  The third mast is a “terminal” mast, used for transformer connection.

The long and short arm masts are installed in an alternating fashion on tangent tracks so that the wire zigzags. This is done for the same reason as the prototype railroad does it, to even out wear on the electrical pantograph of the locomotive.

On curved track segments, the short armed masts are placed on the inside of the curve and the long armed masts are placed on the outside of the curve.

Märklin Z-Scale is an exception to this practice since there is only one single arm mast and a terminal mast.

Tower Masts

For areas such as stations where there are a number of parallel tracks, tower masts and span wires are used.

Depending upon the catenary manufacturer, model span wires have different fittings to hold the individual catenary wires. In some cases, the span wires are trimmed to fit the situation, while in others, these wires are of fixed size.

Once the masts are secured, the individual fittings are located in the span wire and the individual catenary wires are attached.

The Catenary Wires

The individual catenary wires provide electricity to the locomotives Earlier product lines used stamped metal pieces to represent the catenary wire piece, while more recent catenary systems used soldered wires.  The “modern” model catenary systems are quite realistic, a great departure from the past.

The elements of an individual catenary wire piece are the catenary or messenger wire and the contact wire itself. Because the contact wire of the prototype is heavy, the messenger wire is hung higher than the contact wire, flowing in smooth draped curves from mast to mast. Short support wires hold the contact wire in place.

Because the prototype’s wires are heavy, and because the wire needs to be kept in alignment, the masts that support it are substantial, with concrete bases to hold things in place. Also, because the catenary wire expands and contracts as a result of heat and cold, tensioners (such as on the right) are commonly found hanging from support masts.  These devices have heavy concrete pieces to add weight to maintain the necessary tension.

The Locomotives

The models of electric locomotives replicate real locomotives in several ways. Generally, they are models of heavy electrics, locomotives which are designed to pull heavy loads. In many cases, these are locomotives that operate at high speeds, and more than a few of these electric units are self contained trains, such as the ICE:

The electrical contact between an electric locomotive and the catenary wire is made via a pantograph.  Generally, older locomotives use a box shaped pantograph.

Newer electric locomotives use a single-arm pantograph, also called a Faiveley pantograph:

The genius of the model railroad electric locomotive is that the catenary overhead wire system can be used to independently control a locomotive.  Each electric locomotive that can be operated in this fashion has a small switch which is used to select operation from the overhead wire or from both rails. The switch is often hidden in plain sight:

Minitrix Class 110

Märklin Z-Scale Class 103

In other cases, you have to look around a bit:

Märklin H0-Scale Rc4

Rokal E10

In many cases, the switch positions will be marked “O” and “U” (over and under).

Possible Problems

Sometimes, the electric locomotive which is set to use overhead power for propulsion does not operate properly.  In this situation, both transformers are able to control the locomotive, which is not as intended.  The solution to this problem is to rotate the locomotive 180° on the track; this orients the locomotive so that the correct wheels are contacting the “common” rail of the catenary equipped railroad.  This problem does not occur with Märklin’s three conductor system (two rails and a center stud contact in the cross ties) since the locomotive wheel sets are both connecting to the “brown” rails of the track. The center stud contacts and the catenary are each connected to the red terminals of the two different transformers.

Another common problem is seen periodically on auction sites such as eBay. The seller of an electric locomotive reports that the electric model locomotive “does not run”.  They often note that the locomotive motor itself runs when bench tested with power applied directly to the motor, but it does not run when placed on the tracks.

In this situation, this is because the selector switch is set for “O”, but the track power is being applied to both rails.  The sporting thing to do in this situation is to advise them of the existence of the selector switch. My experience has been that even when advised of the selector switch issue, most of the auction sellers are just glad to be rid of something which has caused them so much frustration.

Command Control

The question does come up about using catenary powered locomotives with command control such as DCC. In the early days of Märklin Digital, the Märklin Factory advised that they did not recommend this practice because of reliability issues.  In operation, the pantograph did not provide a consistent electrical path for the electric locomotive that was operating from catenary.  With the introduction of load-compensating decoders, this problem seems to have been minimized.

Although it is possible to do so, using command control from the catenary wire still seems to be an ill conceived idea. Given that the typical command control system can control hundreds of locomotives, and given that the track power is always on with command control so passenger cars remain lit, using command control on the catenary wire seems to be ill advised.

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