Trackwork Basics


There are many subjects we feel you should know about trackwork that you will need to consider when building your first model railroad, many of the basics are covered here.

DISCLAIMER: The article that follows will include brand names as a reference only. Neither we who are writing these pages nor the NMRA intend for these brand names to be a recommendation on our parts. In some cases, the manufacturer may no longer be in business or may not be manufacturing these particular products. We leave recommendations to the owners of your local hobby shops or your friends who are model railroaders.

NOTE: The following is Part 1 of a series of articles written by Roger Hensley and published in Railroad Model Craftsman magazine in 1985 on Beginning Model Railroading. The article is reproduced here with the permission of both the Author and the Publisher and has only been edited slightly.

Beginning Model Railroading

This is not the definitive article on trackwork. It is, however, a reliable guide on ready-to-use products that can make your first layouts easier to build, easier to rebuild, and more fun to run. The suggestions that I am going to make come from the experience accumulated over the years of operating a model railroad-oriented hobby shop and, of course, from my own modeling.

It has been said many times that good trackwork is the most important part of successful model railroad operation. This is the truth. The temptation to lay track down quickly to get the trains running is great, and I've succumbed to it myself, so you probably will have already tried your hand at tracklaying by the time you read this. Some of what I will say will already be beginning to make sense to you. As the majority of active modelers are in HO, that is the product area that I will concentrate on, although most of what I will cover will apply to N scale and other gauges as well.

Track is generally made of one of four materials: brass (the gold-colored metal), zinc-coated steel (dull whitish gray colored), steel and nickel silver (the color of a five-cent piece). The first two types have been most common in train sets, but I would suggest the nickel silver. Brass conducts electricity well, but it needs the most care and cleaning. The oxide that it forms is a poor conductor. This means going over the rails with a track cleaning block or car frequently. With the zinc-coated steel, the zinc coating wears away and leaves the steel exposed and steel will rust. The nickel silver is not quite as good a conductor, but its oxide is about as good a conductor as the original This will provide reliable operation.

Sectional track:
Not only are the materials for making track not equal, but track comes in different lengths and shapes as well. New modelers generally use the 9 inch long pieces of sectional track that come in sets. Atlas, one manufacturer, calls their line "Snap Track." Others make similar track, too; some mounted on plastic roadbed. It is made in straight and curved sections with radii of 15", 18" and 22". In addition, "Snap Track" pieces may be bought in 1/3, 1/2 and 2/3 lengths, as well as in small straight and curved fitting pieces.

There are a few simple but important rules to remember when you lay track. The tighter the curve, the smaller the cars and locos you can run. A 15" curve will limit the size of the equipment that can run without jumping the track. For example, an old-time 4-4-0 and 34-foot freight cars may work well on such tight curves, but a modern SD4O-2 six- axle diesel hauling a bunch of piggyback flats will be off the track more than on. It takes about 40" to lay out a circle of 18" radius track, and 48" for a 22" radius. The 22" is better to get around, but if you use a 4x8' sheet of plywood as a basis for your railroad, you will find that 22" does not fit well. You will end up using 18" much of the time as many modelers do through both choice and necessity.

- Click for larger graphic - Let's lay out an oval of sectional track on a 4x8' board just to get the feel of things. The radius is measured from the center of the track to the center of the curve. A circle of 18" radius is 36" across, which is why about 40" is needed. An oval made of twelve 9" straights and a circle of 18" radius will fill out most of the plywood, but won't come to the edges. There is room for another line of track, if you wish, with 22" radius. One less straight piece would be used on each side of the inner oval.

Sectional track uses a slotted clip called a rail joiner to connect the pieces. This piece provides both electrical and physical connections. The fit must be firm and not sloppy Now, it becomes obvious why the track should be fastened down. The movement of the trains will work it loose, derailing the train or breaking the electrical circuit. The holes in the middle of the ties may be used to tack the track in place. This is one way that HO differs from the 0-27 trains many of us grew up with.

- Click for larger graphic - The rail joiners slip over the end of the rail, but they can be misaligned to the point that one rail is on top of the joiner, causing a bump which would be very large on a real railroad. That kind of bump can derail a train, scale or real, so fit the sections together carefully.

There should be no gaps at the ends of the rails on either the curves or straights. Gaps are something for the wheels to fall into, with the same result as humps.

- Click for larger graphic - When you deviate from the basic oval when using sectional or "Snap Track", you begin to see the need for the small fitting pieces. Adding turnouts (track switches) for sidings and crossovers may change the way the sections fit and cause gaps of an inch or more when you bring the oval together. Don't force the sections! Somewhere this will cause a bind or misalignment in the track. Use the short lengths to make a smooth fit.

Adding power and turnouts:
To get electrical power to your track, most of the sets come with a terminal section. Atlas has a set of wires fastened to two rail joiners; these help hide the wires. You can solder wires to the outer faces of the rail, but you run the risk of melting the plastic ties and losing the correct gauge of the track (the distance between the rails).

Rerailer track sections are also made; some look like road crossings. I prefer the straight ones over those that are curved. There are also track crossings at various angles to allow tracks to cross one another or to make figure eights. The sectional track from different manufacturers is normally interchangeable.

A loop will let you run your trains, and a loop within a loop can let you run two trains if you have the power packs for them. However, it isn't until you add turnouts (switches) to connect them or for sidings for industries or yards that the fun of operation comes. (See Wiring Basics)

- Click for larger graphic - Turnouts come in different sizes and quality of construction. The most common sectional track type is a No. 4, which fits roughly in the space of a 9" straight section. The turnout that goes to the left is simply called a left or lefthand and the right, a right or righthand turnout. Both of these have a straight route through them. A wye turnout curves off to both the left and right, but does not have a straight ahead part. The turnout numbers describe the size, and the smaller the number, the sharper the turnout. On a No. 4 the diverging route moves away one inch for every four on the straight side; a No. 6 has a one in six ratio, which means it is not as sharp. It does take up more space, though, since it is longer. In sectional track. you could consider the No. 4 to be like an 18" radius curve and the No. 6 a 22".

While the least expensive turnouts will work fairly well right out the box, they use a thin metal stamping for the movable point rail. The point will occasionally need to be straightened with a needle nose pliers, and the pivot location sometimes needs to be tightened with a small center punch on the riveted types. The better turnouts have points made from the same rail as the stock rails (the outer fixed rails). They may have a notch cut in the stock rails so the points do not pick at passing wheels.

- Click for larger graphic - Another area of difference can be seen in the frog of the turnouts. This is where the rails cross each other. Some turnouts have metal frogs and some bring the rails up to each other, then insulate them with plastic. If a metal frog is insulated but not powered, you may have some locomotives that will stall on the switch. This is more likely in N than in HO. Even in HO, some locos don't pick up power on all their wheels, giving trouble on some No. 6 switches. Atlas has a product called a "Snap Relay" that will power their Custom Line Mark II and III turnouts if you experience this problem. Some turnouts come with a long switch machine mounted on one side, while others have removable machines, and there are also 'under the table' electrical switch machines. There are manual 'ground throw' switch machines, too. Caboose Industries makes one that looks much like the real ones, and it works well. Atlas, Bachmann, AHM, Life-Like, Model Power, Roco and Tyco turnouts are all electrically interchangeable and all use the same size of rail.

Now, after talking about all of this, there is another kind of turnout which matches the above types physically, but is electrically different. Those listed above have the siding electrically live with the same power as the mainline unless an electrical toggle switch is installed. The other kind of turnout is called a selective turnout. It selects the way the power is routed by which way it is thrown. When it is thrown for the siding, the siding is powered and the straight route goes dead. When it is set for the main, the siding is dead. This creates a different wiring situation, and you must be certain that the rails leading out of the turnout are properly insulated to prevent shorts. This is no problem at all, but it is different from the turnouts that you will usually use on your first layout.

Although I don't want to go too deeply into this matter, I will point out that rail comes in different sizes. Most HO sectional track products are code 100, which means that the rail itself is .100" high. Code 70 and 83 are also used in HO; they scale out closer to actual common rail sizes, and are .070" and .083" high, respectively Some of the manufacturers that make products with these sizes include Walthers/Shinohara, Rail Craft, BK and Railway Engineering. This is not a complete list, by any means.

Note: For the technically minded, more information on rail size in the various scales and their relationship to Prototype weights can be found in the N.M.R.A. Standards and Recommended Practices RP-15.1 - Rail

A brief comment on gauge, the distance between the rails, is also appropriate. The standard gauge in North America is 4' 8". Other gauges were used, with three feet being the most common in the U.S. To show that a narrow gauge is being used on the model, an 'n', followed by the gauge, is used after the letters for the scale. So, HOn3 means HO scale narrow gauge with three feet between the rails.

Flexible track:
We have covered almost all the basic track pieces that you'll need to put things together. The next piece is my personal favorite track, the three-foot piece of flexible track. This is probably the standard track type on the majority of model railroads today. Flexible track pieces are made by most of the track manufacturers, but there are some differences here as well. Most brands are fairly rigid, but bendable. You form them to shape and they stay that way more-or-less. Atlas' Super-Flex, however, has one floating rail and one fixed rail. This makes it easy to bend, but when it is released; it springs back. It depends upon your likes and dislikes, and what you get used to.

The beauties of flexible track are many: fewer joints in a run, the ability to curve to a chosen radius, being able to be gently eased into curves instead of going right into them. A three-foot section of flexible track will replace four 9" pieces of sectional track, so with fewer connections to worry about, you have a big plus for the flex. You can make the curves to be what you need instead of being trapped into fixed radii that don't exactly fit the area.

As far as using flexible track, here are a few practical notes. I like to draw lines for my track to follow to be certain that I don't go under whatever minimum radius I have selected for the location. Sometimes I will use a length of flex track as a template, drawing around a temporarily laid piece to work out the track locations and get them smooth. A pencil, string and yardstick do wonders for laying out the track, but actual track laid down is better. There are track tools sold to insure the radius of a curve, but a yardstick, pencil and some extra track lengths have always served me well.

- Click for larger graphic - The key with flexible track, as with sectional track, is to let your track do everything smoothly: no sudden curves or kinks, and no sudden ups or downs either. You can run into this when you fasten your track down or when you begin to climb or finish a descent. You have to sneak into grades or you'll have a bump or dip. You could hang up the pilot of a locomotive, too, if the grade starts up sharply and quickly. Put your eye down at track level and sight along it to keep things flowing, and be especially careful on bare plywood, which often is uneven. If you see any kinks, bad joints or bumps and dips with this eyeball method, straighten them out right then and there. Derailments will result either at the problem spot or just beyond.

Flexible track does not always have provisions for rail joiners. On those brands you have to trim away the ties completely or the spikeheads and just a bit of the tops of the ties, using a knife. This latter way allows the rail joiner to fit on the rail, yet still be supported by the ties.

You will notice that the rails will shift in relation to each other as flexible track is bent. You have to cut the ends even, and this means trimming the inner rail, which sticks out beyond the outer one. A small modeler's razor saw can be used to cut the rail. Regular wire cutters (diagonals) do not cut the rail squarely; special rail nippers that do cut the rail squarely are sold. You can always cut the rail just a bit longer than needed and file it to fit. When you bend the rail, again follow the rule of doing it smoothly, letting the curve begin gently. Flexible track can also be cut to any length needed, obviously

How fast can you climb to get over a track? I mentioned grades a short time ago. I really like a maximum of 2%, 2" climb in 100" of track (this can be rounded off to 96", or eight feet). When you are limited to a 4x8' board, you either don't climb or you go steeper than 2%. My maximum is 3%, 3" per 100", and I find that I have no serious problems with it. A 4% grade is getting pretty steep and really affects the ability of an engine to haul a train a lot. I have seen some trestle sets that worked out to be nearly 8%; some locos made it to the top and others didn't.

There is another way to get clearance between two tracks. If you lower the track underneath at the same time you raise the upper one, you still get the 3" or 3 1/2" that you need in HO under a bridge. This improves scenery possibilities, too. The last thing to remember is to begin grades at less than the climb rate at the top; make a smooth transition between grades and level track.

- Click for larger graphic - Roadbed:
I would be remiss if I omitted some discussion of roadbed. This is what real track and ties sit on. First class railroads spend a lot of time keeping it in shape on the mainline. Smaller roads, yards and branches do not get as much care. Adding roadbed under our track smooths out the plywood, which we will call sub-roadbed, deadens the sound, makes it easier to fasten the track in place with small track spikes or brads, and provides the raised right-of-way. I like at least 1/2" sub-roadbed under my track; plywood well supported with cross-members or risers periodically is good. Some of the products used for roadbed are the commercial boards Homasote® and Upson Board®. These are sold in lumber yards and are cut up to the shape of the track by the modeler, For ready-made roadbed, there is vinyl, foam and split cork from several companies, split Homasote® and a wooden roadbed. At least two firms make a flexible self-adhering asphalt type of roadbed, too. As you can see, you have a choice.

In my shop I sold a lot of the vinyl and split cork products. To install them, you draw the centerline of the track on the sub-roadbed, then use white glue thinned 50:50 with water to fasten them, if appropriate. Thinning the glue makes it easier to take up later if you decide to make any changes. The split cork goes down a half at a time, following the centerline. You may have to lightly tack the roadbed in place on curves; use brads and remove them when the glue is dry The vinyl roadbed has to be laid carefully, since you cover up the track centerlines with it. You can use the split line on the cork for a centerline.

The vinyl and asphalt roadbeds may be cut with a utility knife or scissors. At turnouts I lay the curved piece over the straight piece and cut them together. Scrap pieces are used to fill gaps and to support switch machines. When you install the track, make sure you don't compress the roadbed when the track is tacked down. This will cause those ornery dips. On sectional track I use every other hole in the tie centers.

When you put in a turnout, remember that the throwbar must remain free. If it binds on the roadbed, trim away some of the roadbed to free the turnout. One note about split cork roadbed: when you go around curves, the ends of the pieces will not line up - just overlap them. The same is true for the pre-cut Homasote® pieces. Before I get any letters, let me say that you don't have to lay your entire roadbed half at a time with these split types. By all means have each half progress along with the other. And, where you need some shims to level track or to make a transition to a yard area, card stock will work fine. The roadbed itself will eventually be hidden by ballast (fine sand) to represent the gravel on the prototype, anyway, so the shims are fine. Roadbed is like the rest of the railroad. There is no correct way and no correct material for every situation. You do what works best for you.

I have tried to touch on some of the basics of track here, using things that I've learned over the years. We will talk about wiring, scenery and other topics later. In the meantime, a visit to a nearby hobby shop will put you in contact with people who can help you with questions and show you some helpful books on model railroad building.

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Page last updated December 2, 2014