How To Model Railroad Operations Why railroads put locomotives in the middle of a train

Why railroads put locomotives in the middle of a train

By Drayton Blackgrove | April 5, 2023

Why do railroads put locomotives in the middle or even on the ends of their trains sometimes, and can I run my trains that way?

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Showing why railroads put locomotives in the middle of a train, a loaded CSX Transportation coal train with mid-train distributed power rolls into St. Albans, W.Va., on Jan. 27, 2018. Chase Gunnoe photograph

Railroads are one of the most efficient modes of transportation for moving goods and materials across long distances. However, there are certain challenges in terms of locomotive power and efficiency, which is where the concept of distributed power comes in. Distributed power is an operating practice where locomotives are placed throughout the train. Typically in the middle, but often found two-thirds from the rear or on the tail end, each locomotive provides enough power to move a certain number of cars at a specific tonnage ratio.

Beginning in the 1960s, mid-train distributed power units – DPU – and pushers have been operated using radio signals. Southern Railway pioneered this technology, adopting an early form of Locotrol. The North Electric Company, an Ohio-based manufacturer of telephones and electronics, created Locotrol with the technology later acquired by Harris Controls Systems Division of Harris Corporation, predecessor of GE-Harris Railway Electronics.

Originally, the electronics were placed in a separate railcar as the equipment was bulky and generally did not fit inside a standard locomotive cab or nose. Over time, the radio gear was condensed into relatively small cabinets, with most of the functions being controlled by software. Today, numerous railroads worldwide have installed Locotrol on their locomotives with thousands of systems in operation.

One of the primary reasons railroads use distributed power is to increase the pulling power of the trains as the length and weight also increases. By placing additional locomotives in the middle or at the end, the overall pulling power of the multiple locomotives increases, moving the train efficiently and effectively.

Another benefit is that it allows for greater control and flexibility in the train’s speed and acceleration with the locomotives operating independently. This is particularly important when it comes to braking as distributed power enables trains to stop more quickly and smoothly, reducing the risk of accidents and derailments.

Distributed power also enables railroads to run longer and heavier trains by spreading the power across multiple locomotives without exceeding their limits. This can result in fewer trips, lower fuel costs, and increased revenue for the railroad. It also improves safety as each locomotive is connected to the train’s electronic control system, which enables the crew to monitor the overall performance and detect any problems before they become serious.

There’s also a competitive advantage for the railroad over other modes of transportation. Since freight trains can haul more volumes at higher efficiency than trucks and airplanes, distributed power helps make rail transportation a more viable and attractive option for shippers and carriers. Shipping commodities in bulk also reduces the overall cost for shippers and customers can transport even more products via rail at a reduced rate.

There are some challenges associated with distributed power that need to be considered. For example, the additional locomotives required increases the fuel cost associated with operating the trains and can require additional maintenance and operational costs. In addition, the complexity of the system can sometimes make it more difficult to troubleshoot and repair problems.

Despite these challenges, the benefits of distributed power outweigh the drawbacks, and it is now considered a standard practice in the railroad industry. In fact, some railroads have gone even further and have implemented advanced systems that use sophisticated algorithms and computer software to optimize the train’s performance and reduce fuel consumption. As the technology continues to advance, we can expect to see future systems that will further transform the way we think about rail transportation.

So… how does this play into model railroading?

Since distributed power is commonly used in full-scale trains, you might want to implement this practice into running your own model trains. Just like the real thing, adding a distributed power unit can improve your train’s overall performance, including acceleration and speed control. You’ll also be able to pull more cars and reduce stress on plastic couplers.

You will need to place additional locomotives throughout your train, whether in the middle, near the end, or as pushers on the rear. Then, you’ll need to consist the locomotives together, so they operate in unison with your lead unit.

A trio of diesel locomotive models pulls a coal train on an HO scale model railroad layout.DCC consisting allows three diesels leading a coal train on the HO scale Milwaukee, Racine & Troy. Bill Zuback photograph

“Consisting” – the ability to control multiple locomotives as a single unit – is achieved by assigning each one in the consist as a unique address, then linking them together in the DCC system. Consisting can be particularly useful for model railroaders who want to run longer trains with multiple locomotives working together. It can also be used to achieve more realistic operations.

When operating a consist of multiple locomotives, it is important to ensure that each locomotive runs at the same speed as the others. Even the slightest variations in speed between locomotives can cause jerky or uneven movement, which can be noticeable and detract from the realism of the train operation. They can also cause your train to derail and break couplers. If your locomotives are not speed matched, there are tutorials that explain how to do this using your DCC system.

To create a consist, you must first select the locomotive you want to lead the train. This is done so by acquiring the road number of the unit. Then, you’ll link your locomotives together using a DCC system, usually by pressing a “consist” command on the controller to group the locomotives. Once they’re linked in a consist, the system treats them as a single unit, allowing you to control all the locomotives together. This means that you control the speed, direction, and other functions of the entire consist with a single command.

So, the next time you’re at a model railroad club or a friend’s layout, give distributed power a try by consisting your locomotives together. It’s fun, looks prototypical, and can enhance the operation of your model trains.

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