Very few railroads had the luxury of being built on a completely level route. To climb hills and mountains, railroads need grades. A lot of engineering and planning goes into grading a right-of-way to ensure that trains can ascend and descend efficiently and safely.
Grades add visual and operating interest to a model railroad. Installing a grade is not difficult, but it does take a little planning.
How Steep is Too Steep?
One of the first questions that comes to mind with any grade is how steep it should be. Grades are measured by the rise over the run in terms of a percent. So a 1% grade will rise one unit of measure over a run of 100. On the prototype, a grade of 2% is considered steep for a mainline. Branchlines, industrial spurs, logging operations and other lines where tonnage and speeds are reduced may see grades of as high as 4 to 6%.
Model trains are much more tolerant of grades. Our trains are generally shorter and weigh much less, so the forces of physics are minimized but still present. Grades of 2 to 4% are usually not a problem for most model trains. Above that, you may have to put some tight limits on how many cars your engines can pull. Another consideration is that grades steeper than 4% usually look too steep to be realistic even if they are manageable.
Calculating the Grade
When designing a model grade, it is easiest to start at the top and work down. In almost every case, the rise will be less variable than the run. Find the highest point of the grade, for example where the track needs to cross over another, and work back to the bottom.
Generally speaking, the longer you can make the grade the better. Just because your train can climb a 4% grade doesn't mean it has to. Sometimes you may be forced by the space available to a tight or curving grade. When you have options, here are some things to consider:
- Curves: Curves can be both a blessing and a curse on a grade. They lengthen the run and can actually help on descents by causing more friction. They also often appear more natural, especially in mountainous scenery, and hide the severity of the grade. On the other hand, especially sharp curves will require further reductions in speed. Reverse curves and curves at the bottom a grade also place a lot of stresses on a train and should be kept gentle or avoided if possible.
- Easements: Gradual entrances to the start and end of a grade, just like with curves, make the transition from level to grade much easier on equipment and improve operations. A vertical kink in the track can be as problematic as a horizontal kink.
- Turnouts and Sidings: Adding switches on a grade is fine, but it is best to keep sidings where cars will be parked without a locomotive as level as possible. If you are going to put a spur on a grade, put the entrance at the uphill end. This will prevent the cars from rolling back onto the mainline. A turnout at the bottom of a grade, especially a sharp one, is also more prone to problems.
Once the length and route of the run has been determined the grade can be calculated and measured off.
Building the Grade
There are several ways to build a grade. Several manufacturers make pier and trestle sets designed to lock into track sections. While not the most prototypical in appearance, these sets are easy to install and easy to change for temporary layouts. Woodland Scenics Styrofoam grades are another alternative for those who don't want to make cuts in their train platforms.
For a more permanent installation, benchwork can be easily modified to accommodate a grade with a smooth transition at the base. The following steps will work for any type of benchwork. L-girder and open-grid benchwork construction doesn't feature a solid table-top, so you can eliminate some of the steps, but the process is the same.
- Trace the area to be raised. Leave ample clearance on either side of the track for ballast and scenery.
- Cut along the lines the length of the grade. Leave the plywood attached at the ends of the grade for smooth transitions. If your grade crosses multiple pieces of plywood, it is best to make joints in the middle of the grade, not at ends where you'll want a smooth easement.
- Support the grade. Wood blocks can be inserted at regular intervals to support an even slope. As with planning, it is often easiest to start at the top and work toward the base.
Supports should be inserted every 12 to 16 inches on average. The height of the supports can be figured with some simple math, taking the total rise of the grade and dividing by the number of supports if the supports are evenly spaced. If you can't space all of the braces on even centers, it may be easiest to calculate as many as possible and insert intermediates by eye.
- Secure all supports with screws and glue for a sturdy base.
Track can now be laid and wired. Consider installing extra wire feeders on grades to ensure a steady power supply where it will be needed.