1. Home
  2.  ›
  3. Steam Locomotives
  4.  ›
  5. Baker Valve Gear

Baker Valve Gear

Published: September 21, 2023

By: Adam Burns

The Baker valve gear, a crucial component of many steam locomotives, was the brainchild of an Akron-based inventor named Abner D. Baker. Originating from Ohio in the United States, Baker invented and patented the valve gear, which carries his name, in the early years of the 20th century, specifically in 1909.

The Baker functions as a critical control mechanism in steam locomotives, facilitating precise regulation of the inflow and outflow of steam within the machine's cylinders. It operates by maneuvering the slide valve, which opens and closes the steam ports, thereby dictating the motion of the pistons and, by extension, the wheels of the locomotive.

Essential elements include the bell crank, main link, link block, combination lever, and radius rod, among others. These components harmoniously collaborate to control steam admission to the piston, and subsequently its exhaust, transforming the mechanical potential into kinetic energy for propulsion.


304986871325151895891278689378988.jpgNevada Northern 4-6-0 #40 is seen here leading an eastbound excursion through the Keystone Canyon on February 8, 2015. This little Ten-Wheeler, built by Baldwin in 1910, employs Baker valve gear. Drew Jacksich photo.


In America, the Baker valve gear enjoyed a significant level of recognition and use amongst steam locomotives due to its mechanical ingenuity and perceived efficiency. The mechanism’s appeal was primarily its lightweight, less complex design compared to previous designs - features that enhanced locomotive resilience and control.

However, as the 20th century progressed the Baker fell out of favor with most of the industry.  Its longevity and reliability were overshadowed by the inherent complexity of its assembly, a contrast to the simplicity of alternatives like the Walschaerts valve gear. Nevertheless, its impact in steam locomotive evolution remains a vital chapter in the annals of locomotive history.

Other Types

To fairly assess the Baker valve gear, it's pertinent to compare it with contemporaries, such as the Stephenson and Walschaerts valve gears. These mechanisms represent distinct approaches to the same fundamental task—manipulating steam flow to generate rotational force for a locomotive's wheels.

The Stephenson valve gear, invented by British engineers George and Robert Stephenson, was a popular system during the initial era of steam locomotive development.

It remained the preferred type used by most American railroads throughout the 19th century.  This gear’s characteristic trait was the use of two eccentric rods, in contrast to the single one found in the Baker valve gear.

The Stephenson gear was an efficient system but was increasingly seen as complex, especially regarding adjustments after installation.

This perceived complexity, coupled with significant space requirements, pushed engineers to explore more flexible and streamlined solutions, leading to the development of systems like the Baker valve gear.

The degree of its adjustability was an improvement over the Stephenson system. Baker's design offered a smooth operation, allowing locomotive engineers to adjust the arrival and duration of steam within the cylinder more accurately.

However, the the Walschaerts design ultimately became the preferred type by the early 20th century, notably with the development of "Super Power" technology by the mid-1920s.

Engineered by Belgian Egide Walschaerts, this valve gear had the advantage of separate and easier adjustments for the locomotive operator, a feature highly appreciated for efficient steam management.

The Walschaerts valve gear, despite being an older invention than the Baker, demonstrated a sturdier, yet simple design.

The latter, while innovative and lighter, had an intricate array of smaller parts leading to potential complications in maintenance and repair work.  By contrast, the Walschaerts was robust, simple to maintain, and easier to carry out fine adjustments.

Abner D. Baker

The Baker valve gear nonetheless played a crucial role in propelling the era of steam locomotion forward.  While it eventually fell out of favor with most railroads it was well-liked by the Baltimore & Ohio, Chesapeake & Ohio, New York Central, Nickel Plate (New York, Chicago & St. Louis), and Norfolk & Western.

Abner D. Baker’s invention reflected a thoughtful attempt to evolve and refine what was then considered to be the optimal system for controlling steam in locomotives.

He introduced his invention at a time when there was a demand for more efficient and reliable valve gears—a demand that Baker's design partially satisfied.

While the Baker valve gear might not enjoy the same limelight as the Walschaerts valve gear today, especially among heritage and tourist railroads, it remains a significant chapter in the story of steam locomotive progression.


At the heart of the Baker valve gear is a fundamental mechanical principle—conversion of linear motion of pistons to a rotational motion driving the wheels of a steam locomotive. This principle is exploited and optimized in the Baker valve gear design to controls the delicate dance of steam within the heart of a locomotive.

The bell crank, main link, and linkage arrangement are just some examples of the mechanical brilliance embedded in the Baker valve gear. It includes its ability to adjust the cutoff and admission exhaust of steam—independently and while the locomotive is in motion—a feature that was poised as a game-changer in the locomotive world.

This vision, conceivably inspired by the strengths and limitations of the Stephenson valve gear and the growing popularity of the Walschaerts valve gear, was a genius of engineering creativity.

In his book, "The Steam Locomotive Energy Story," author Walter Simpson notes that during the "Super Power" era of locomotive design, which began with Lima Locomotive's 2-8-4 wheel arrangement of 1925, most new engines were equipped with either Walschaerts or Baker valve gear.

As a study piece for engineering students, the Baker offers an interesting exploration of mechanical systems in action. It provides a vivid demonstration of how applied principles govern powerful machines, showing how calculated adjustments can harness uncontrollable forces to execute controlled, valued outputs.

The Baker valve gear redefined steam regulation, a newfound rhythm in the symphony of steam locomotion. Its invention was a sober revelation of the enormity of opportunities that lay hidden in the world of machines, awaiting exploration and unravelling by curious minds.

As learners, engineers, and enthusiasts gather to dissect the history of steam locomotion, the ghost of the Baker valve gear often touches the conversation. Revered and remembered, its lessons continue to dictate current principles and guide future innovation.

Capping off our extensive delve into the Baker valve gear, it seems fitting to revisit its purpose; controlling the might of steam in locomotives. It was a critical bridge in our journey from brute mechanical muscle to the finesse of flawless function.

Sculpted out of iron, steam, and human ingenuity, the Baker valve gear is a beacon of historical engineering prowess and a testament to the transformative power of invention.

It remains a marvelous symbol of our continued struggle to master energy, space, power, and time, making it an immortal legend in the annals of locomotive history.


  • Dixon, Thomas W. Norfolk & Western Steam:  The Last 30 Years.  Forest:  TLC Publishing, 2013.
  • Edson, William D. Steam Locomotives Of The Baltimore & Ohio: An All-Time Roster.  Potomac: William D. Edson, 1992.
  • Morrison, Tom. American Steam Locomotive In The Twentieth Century. Jefferson: McFarland & Company, Inc., 2019.
  • Simpson, Walter. Steam Locomotive Energy Story, The.  New York: American University Presses, 2021.
  • Solomon, Brian. Alco Locomotives. Minneapolis: Voyageur Press, 2009.
  • Solomon, Brian.  Baldwin Locomotives.  Minneapolis:  Voyageur Press, 2009.


Wes Barris's SteamLocomotive.com is simply the best web resource on the study of steam locomotives. 

It is difficult to truly articulate just how much material can be found at this website. 

It is quite staggering and a must visit!