The flat car goes back to the beginnings of railroading and is often referred to as the "universal" car because of its versatility. Just as it does in revenue service, the flat car also has many uses in maintenance of way service. This opens up a world of possibilities for the modeler. There will be three types of flat cars discussed here. They are the un-modified flat, the moderately modified flat, and the flat which has been modified to such a degree that it is hard to determine whether it is still or has ever even been a flat car.
First in this parade of flat cars is the flat car which has been modified to such a degree as to no longer be in the universal carrier that it was in the past. The most obvious example of this car is the flat which has had a major superstructure added for use as a Relief Tender with a wrecker (see photo). The 120-ton wrecker usually was the one which used the modified flat.
Second comes the partially or moderately modified flat car, where the load determines the modification of the car. This is one of the largest areas of maintenance of way usages of the flat car. For example, SPMW 4973 is a standard 50-foot flat car that has had cradles either bolted or welded to the floor of the flat. These cradles are designed to hold two prime movers (diesel engines), either GE or EMD, though the cradle will be a little different to take the motor mounts of the individual prime mover. The reason the prime movers are shipped this way is because the railroad has found it easier and more economical to send the movers back to the manufacturer rather than to maintain a large supply of spare parts on the property.
A sidelight of this is that if you can acquire an old AMT auto customizing kit for an Allison (GM) V-12 engine and make a mold of the halves for casting others, you can make a whole series of EMD prime movers from this base and mount several on flats and have several more in the engine facility. This engine flat can be used in a train consist for use in interchange. SPMW 4973 is shown "in train" at Espee's Taylor facility in Los Angeles bound for La Grange. This can expand your runs and use these types of cars to put the realism of distance into the layout.
Wheel flats and rail flats for use with the continuous welded rail machines also fits into this category.
The final type of flat to be discussed here is the basically un-modified flat car. This is the standard flat car which has been re-numbered into Maintenance of Way series and is used for just about any thing the maintenance people can think of. For example, SPMW 9300 is used to carry 25-ton industrial crane SPO-51 over long distances and uses standard tie downs and 6x6 wood blocks nailed to the flat car floor wheel and track guides as would be done if this flat was in revenue service carrying a crane for a customer. The boom of the crane is held by a king-size saw horse.
Usually, when an object like crane SPO-51 is transported it also requires a myriad of attendant parts so the crane may do its job. These parts, such as boom extensions, clam shell buckets, and the ramp to get the crane off the flat that it is on. SPMW 4479 is shown in service as the attendant car for SPMW 9300.
Not illustrated, but also very important in this class of flats, are a number of bulk head flats which are numbered in the M-W series and used to carry 40 foot sections of track (the prototype's equivilent of snap track) to the scenes of derailments so that a minimum of down time will occur. Also, there are a number of flats assigned to the transporting of ties.
This piece is by no means a complete listing of all the Maintenance of Way uses of the flat car, but it is designed to give the reader a general idea of how the venerable flat car may be used in the area of maintenance. It is hoped that the reader will take advantage of his/her imagination and put together a number of these flats to go with a work train or wreck train or as part of a revenue train.