Behind The Scenes Trains Live Trains LIVE — Articulated locomotives

Trains LIVE — Articulated locomotives

By Bob Lettenberger, Trains Associate Editor | February 3, 2023

From simple to Mallets, we're talking flexible locomotives in all sizes

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Trains LIVE — Articulated locomotives

Trains LIVE — 2-1-2023 — Flexible is good, especially when it comes to large steam locomotives negotiating a curve. Today, we are talking about articulated steam locomotives with Trains video producer Kevin Gilliam today. Kevin is currently working on the next DVD in the Great American Steam Locomotive series. This one is all about articulated locomotives.

Railroads found themselves in an interesting cycle when it came to developing steam locomotives with increased power. Greater tractive effort generally meant a larger boiler to produce more steam. The bigger boiler weighed more necessitating additional wheels for support. At some point — eight, 10, 12 driving wheels on a straight frame — locomotive began having trouble negotiating curves.

The solution was provided by Anatole Mallet, a Swiss-born engineer practicing in France, who placed two sets of driving wheels under one boiler. Each set of drivers had their own cylinders. One set, or engine, was attached to the boiler. The other set — the lead engine — moved independent of the boiler, yielding greater flexibility to moved around curves.

While articulated locomotives are generally thought of as big machines — think Union Pacific Big Boy or Duluth, Missabe & Iron Range Yellowstones — Kevin mentions smaller logging and mining engines that were flexible, as well.

Come along for Trains LIVE — Articulated locomotives.


Trains LIVE is a regular video segment, recorded live and unscripted from Kalmbach Media. The series began in July 2022.

Trains LIVE features Bob Lettenberger, Trains associate editor, Kalmbach Media staff, and guests talking about railroads and trains in a casual, behind the scenes format. On Trains LIVE we will ask the questions you would like to ask and take you into places not normally open to the public. Trains LIVE also takes you on the road to museums, trackside locations and other railroad-related venues. It is unscripted and presented every other Wednesday at 2 p.m. Central time.

If you have questions or comments, please log-in and leave a comment in the area at the bottom of the page. We will attempt to answer questions during future episodes. 
All aboard! It’s time for Trains LIVE!

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