You’ve learned by now how cargo containers like the Boomerang Box are lifted off ships and put onto trucks when they need to travel across land. But how do containers travel when they are going long distances? Do containers always travel one at a time on the bed of a truck?

No, not always. If a container is traveling a long way over land, it most likely takes a stacktrain. What’s a stacktrain? Well, just as the name says, it’s a train that stacks the containers, two on each train car, so that each train can carry twice the number of containers as it has cars. Pretty smart, huh?

Stacktrains were first developed by APL in the 1980s as a good way to get cargo around the country quickly and safely. Since 1999, APL’s stacktrain service has been owned and operated by a company called Pacer Stacktrain. Pacer Stacktrain sends trains filled with cargo containers all around the country. And it uses all the latest technology to make sure that its trains make the safest journeys possible... to keep the cargo inside those containers safe and sound even as the train clicks along the rails up and down hills and around curves.

Since you’ve been following the Boomerang Box, you know all about how cargo containers are kept safe and stable on ships: how containers are carefully and gently lowered onto the ship by a crane; how containers are balanced throughout the ship so that one side of the ship won’t become too heavy; and how the containers are locked into place on the ship so that they can travel to the other side of the ocean without budging, even in a storm.

Pacer Stacktrain has thought about the same kinds of things... except on rails instead of on a ship. To keep cargo on its trains safe, Pacer Stacktrain has carefully designed its trains to limit the amount of longitudinal (back-and-forth), lateral (side-to-side), and vertical (up-and-down) motions they make. Because, while a roller coaster speeding along the rails on its track might be a lot of fun for you and me, you certainly DON’T want your new computer banged around on a wild train ride before it gets to you!

Here’s how Pacer does it:

Longitudinal (back-and-forth) movement happens between train cars when the train goes up or down a hill. Going up, the connections between all the train cars stretch out; going down, they come together again. Kind of like a bungee cord! In fact, a typical stacktrain with 50 to 60 cars can have 125 to 150 feet of this kind of movement (train engineers call it “slack action”). Unfortunately, train cars that move back and forth like that don’t do a very good job of protecting cargo. So Pacer Stacktrain has designed special fixed connections between its cars. These new connections cut down on the bungee cord action, keeping the train cars in line and the cargo steady.

Lateral (side-to-side) movement happens as train cars sway or roll as they move along. Think about a roller coaster again. A lot of the fun is the way you get pushed from side to side as you go around turns. But, again, what’s fun for you for a few minutes on a roller coaster is definitely bad news for cargo. Pacer Stacktrain has gotten on top of this kind of movement as well. It sets containers down low on the train cars — just 12 inches above the rails — and then connects the cars so that when one is swaying in one direction, the car behind it will sway in the other direction. This way, the train and its cargo never sway too much.

And finally, the bounce and vibration of vertical movement can hurt cargo when the wheel assemblies of each train car are put too far apart. On a roller coaster, the car is designed to try to throw you out! But a stacktrain has to do just the opposite. Pacer Stacktrains have wheel assemblies that are only 50 to 58 feet apart compared to 80 feet for other types of trains. That means a lot less bouncing for your cargo.

All things considered, you might find a ride on a Pacer Stacktrain very boring indeed. No thrills, no spills. But then, if you want a wild ride, you can always find a roller coaster... and in the meantime, you’ll know that all the things you use that came to your town by train arrived in shipshape condition.