How do Lionel trains work?

Lionel trains entertained kids for generations, and inspired some to become engineers. And not just train engineers. Sometimes it inspired them to electrical or mechanical engineering. But how do Lionel trains work? Let’s step through it.

A Lionel train is just a flow of electrons. The hot wire from your electrical box goes through a transformer to the center rail, then through the motor and out to the wheels, through the outer rails and back to the transformer and finally, back to the outlet and out of your house back through the panel.

The best science lesson I ever received

how do Lionel trains work?
How do Lionel trains work? It’s a flow of electrons and a trick with electromagnets. That makes the motor spin and the gears and wheels turn.

My dad had degrees in physics, chemistry, biology, and medicine. When I was about 12 years old, he explained the physics of a Lionel train to me. I’m repeating that to the best of my recollection here. I’ve had to have a few other people re-explain some of the concepts to me over the years, but Dad covered it. At 12 years of age, I just wasn’t ready for all of it.

How the electricity works, in detail

In North America, household electricity is alternating current. This means it reverses polarity 60 times per second. Alternating current runs on two wires, a hot wire and a return wire. In AC, the hot wire is the black wire in the outlet. The white wire is the return. There’s a third wire that runs literally to ground. That’s why that third prong is called ground. Lionel trains don’t normally use this one.

The transformer

Household current is nominally 110 volts, but that’s an estimate. It can actually be as high as 120. That’s an unsafe voltage to have on exposed metal toy train tracks. Lionel steps that down using a device called a transformer.

The transformer is just a pair of coils that reduce voltage. Voltage is the speed at which the current moves. Amperage is a measure of how much power is there. As far as the train is concerned, more amperage just means you can have more lights on the train.

Voltage is the easier concept to quantify. When you add voltage, the train goes faster. The transformer has a wiper on one of the coils that determines the speed. When you move the handle, it moves the wiper up and down the coil. At full throttle, the transformer can deliver 18, 20, or even 24 volts. At minimal throttle, most Lionel transformers 6 volts or less.

The electron’s journey as it rides the train

The power flows from the service panel to the outlet, to the transformer, then through the center rail into the motor, then out through the wheels and the outer rails back to the transformer, then back to the panel. That’s the journey an electron takes to make a Lionel train move. Each electron spends more time on the wire than it does on the train. It travels a long way to take a short train ride.

How a Lionel motor works

The Lionel motor is just a collection of four electromagnets. In magnetism, opposites attract. Electric motors keep the opposites from ever meeting.

The wire from the center rail flows through a wire that’s wrapped around a collection of steel plates. This is called the motor field. It’s just a big horseshoe electromagnet. The polarity of the magnet determines what direction the train goes.

The wire goes from the field to a piece called a brush. It’s usually just a lump of graphite. Graphite conducts electricity well enough for these purposes. The current flows from the brush to a series of three copper plates. Only two plates are ever energized at one time. The two plates power one of the magnets at a time. As the field repels the magnet, the brushes cut power from that one and energize another magnet. This tricks the magnets, so the north and south poles from the three magnets, called an armature, never meet their opposite on the field.

When the armature turns, it turns a gear, which turns a series of gears that turn the wheels and make the train move.

Most Lionel trains have a solenoid in them that activates when you cut the power. The solenoid cycles through a series of contacts on a drum that either cut power to the motor to put the train in neutral, or reverse the polarity on the field, to make the motor go forward or backwards. This device, called an e-unit, was revolutionary in the 1920s and Lionel bought a rival company, Ives, to get that coveted e-unit.

What about that third rail?

Lionel used a three-rail system for a reason. The main reason, though, was that it made complex layouts very simple, electricity-wise. In a two-rail system, if you connect track from a switch back onto itself, you cause a short circuit. With a three rail system where only the center rail is hot, you don’t. The three-rail system made this kind of a layout work at the turn of the previous century without any expensive complexity.

Two-rail systems have to reverse the track polarity in this situation, or just not have a layout reverse on itself. In a two-rail system, one rail is hot and the other rail is the return, and the wheels are isolated from each other electrically to prevent short circuits. In the 1940s, none of this was especially difficult thanks in part to the ready availability of plastics, so two-rail systems caught on after World War II. Lionel had a two-rail system when it first started out, but quickly switched to a three-rail system to make a simpler, less expensive train that didn’t require anything that was exotic for the turn of the previous century.

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