Why Railway Air Brakes Matter

One of the greatest inventions that changed the world was the steam locomotive. However, when the steam locomotive first came to be, its brakes weren’t as great at stopping when hooked up to other cars— until the creation of the air brake system. In the following, we will discuss the different types of railway air brakes, the history of air brakes, and how they are being used today.

How Do Air Brakes Work?

In some ways, steam locomotive air brakes resemble the brakes on a motor vehicle. They both play an important job—stopping your forward motion. Air brakes use pressure from compressed air to squeeze the wheels to a standstill.

Parts of an Air Brake

There are several different parts that make up an air brake system:

  • A source of compressed air, like an air compressor, on the locomotive. 
  • A brake pipe to connect the locomotive with the cars on the train.
  • A control valve, which can be either manual or automatic, to apply and release brakes.
  • A brake cylinder with a piston that the compressed air acts on to transmit power from the compressed air through mechanical linkage to brake shoes that act on the wheels to slow movement.
Part of a railway air brake

Different Types of Air Brakes

Like most things in life, air brakes evolved over several different systems to become the sophisticated one that is still used today.  

The Vacuum Brake

These were once used in the United States but were more common, and were used longer, in Europe. Today this system is now obsolete.

It had a continuous pipe called the train pipe, that ran the length of the train. Normally a partial vacuum is maintained in the train pipe, and the brakes are released. When air is admitted to the train pipe, that air acts against pistons in cylinders in each car. 

A vacuum is sustained on the other face of the pistons so that a net force is applied. A mechanical linkage then transmits this force to brake shoes, which act on the wheel treads.  

The working principles of a vacuum braking system and an air braking system are similar but the process and source to apply the brakes are different.

The Straight, or Direct, Air Brake

Straight air brakes work by supplying compressed air to the brake cylinders on the cars of a train from a single reservoir source mounted on the locomotive. In order to apply the brakes on a train with this system, the engineer would operate a valve in the locomotive cab that would send compressed air through the brake pipe connecting the cars with the locomotive to the brake cylinders on the train. The advantage of this system is its simplicity—there are very few parts. 

However, for railroad service, it has several drawbacks. It did not work well on long trains because it would take time for the compressed air to reach the car furthest from the locomotive and the brakes on the train would not apply or release evenly. This could cause violent slack action in the train and put undue stress on couplings and cars.  

Worse than that, if the train were to become parted in the middle, or a hose or pipe connection would burst, the entire train would be left without brakes and could run out of control.

The Automatic Air Brake

In an automatic air brake system, the air is supplied from the locomotive but stored in a reservoir on each individual car, connected by a brake pipe. The brake function on each car is then controlled by an automatic “control valve” on each car that responds to changes in brake pipe pressure.  

The brakes are released when the system is fully charged with air at maximum system pressure. An engineer can apply them from the locomotive, using a manual brake valve that reduces pressure in the brake pipe.  

Control valves sense the pressure change and allow compressed air, stored in the reservoir on each car, to move into the brake cylinder and apply the brakes on individual cars. 

When the brake pipe pressure is recharged the brakes release. The control valves sense the pressure increase and vent the air out from the brake cylinder to the atmosphere. This causes the reservoirs on the individual cars to recharge, making them ready to apply again when needed.

The advantage of this system over straight air brakes is that the brakes will apply and release on trains, regardless of length, at nearly the same time and at the same speed, making train movement smooth. 

They also are fail-safe, so if the train becomes parted or the brake pipe bursts, instead of having no brakes, the control valves on each car will sense the rapid brake pipe pressure drop and all brakes on the train will immediately go into an emergency application, bringing the whole train to a stop.

Life Before Air Brakes: An Air Brakes History

Before air brakes, trains employed an inefficient, and sometimes dangerous method to stop trains. They required employees known as brakemen to run atop the cars and set each car’s brakes by hand using its brake wheel. Basic brake shoes would press against the wheel slowing its movement. 

However, it didn’t always stop the train in time so you could overshoot the station or stop too short. Brakemen were often maimed or killed by getting hit by low-hanging masonry or by falling off rail cars.

Early steam locomotives were supplied with steam brakes. The same steam source (the boiler) that provided locomotives the power to go also made them stop with a brake cylinder (similar to the later air brake cylinders.) These brakes were only available on the locomotive and were not powerful enough to stop trains with many cars.

Steam brakes couldn’t be applied to cars either, because the steam would cool and lose its power once it traveled any distance through a pipe away from the locomotive. Air brakes were that innovative piece that allowed entire trains to safely stop.

In 1869 George Westinghouse patented a new design for the railway air brake—what we know as the automatic air brake system. It was built by Westinghouse Air Brake Co. The company not only built the system but it manufactured equipment necessary for brakes, like the friction draft gear.

Westinghouse updated their systems to change with new technology and materials and better suit the operational needs of their railroad customers. As time went on, the company evolved from making just air brakes to manufacturing electromagnetic and electro-pneumatic brakes as well.

Railway air brakes weren’t immediately adopted by all railroads. Most railroad bosses weren’t sold on the idea since it meant retrofitting cars and locomotives at a large expense. However, they started to see the system’s value and its use became more common. The Railroad Safety Appliance Act of 1893 made the railway air brake invention mandatory on American trains. It was passed on March 2, 1893, and took effect in 1900 after a 7-year grace period.

Why Was The Railway Air Brake Important?

Ultimately the railway air brake made trains safer. Trains were operated with greater control and accidents were often prevented. And workers, like brakemen, no longer had to ride on the tops of cars to apply brakes manually, thus reducing the dangers of their jobs.

The railway air brake system also permitted trains to travel at higher speeds. This allowed merchants to move their goods from one place to another at a higher profit. Higher speeds also allowed passengers to move more efficiently, allowing commuting from suburban areas into major cities and making things like weekend trips over longer distances practical.

Evolution of the Air Brake

The first brake systems were good for short, slow trains. Improvements were made and new systems were later created that worked better with longer, heavier trains. 

Eventually, systems evolved specifically for passenger trains, which operated at higher speeds but were lighter in weight and shorter in length. This was an important development, since freight trains usually operated at lower speeds, but were much longer and heavier. 

Of all the changes, the most rapid evolution occurred between the 1890s and 1930s, with many innovative systems being introduced. These systems comprised those that were applied to cars and those applied to locomotives. 

Many small changes have occurred since World War II, but today’s automatic freight train brake systems are still very similar to the air brakes used on both passenger and freight trains at that time.  While on the flip side, passenger train brake systems are now mostly electro-pneumatic and combine advanced electronic control with the power of compressed air.

A aerial view of SRR Mechanical's workshop,

Common Repair Problems with Air Brakes

All air brake systems require regular maintenance and repair, some of which are mandated by Federal regulations. Back in the day, railroads, as well as air brake system manufacturers like Westinghouse and New York Air Brake, employed large numbers of specialized craftsmen and specialized equipment. 

Routine maintenance includes cleaning, oiling, and testing of the complex valves that operate and control the function of the brakes on cars and locomotives. This testing is done on specialized racks that brake valves are mounted to and that simulate the function of the valves in service. 

When a valve is in service, it performs many functions simultaneously. The test racks allow the isolation of individual functions to ensure all parts of the valve are working properly or to diagnose problems among the many components in the valves. 

Most of the testing equipment for the now-obsolete air brake systems, used on historic equipment, has long disappeared. At Strasburg Mechanical Services, we have several of these testing racks to use with these systems along with the original instructional material. This allows our highly skilled staff to help repair malfunctioning equipment and keep all valves in safe operating condition.

Strasburg Mechanical Services can diagnose and repair problems within the complete air brake system, from overhauling steam-driven air compressors to sourcing parts for obsolete systems, to brake valve repair and maintenance, as well as system troubleshooting.

At Strasburg Mechanical Services, we prefer to retain the original railway air brake systems on historic railroad equipment. This preserves the integrity of historic railroad artifacts and eliminates the need for a time-consuming, and expensive, modern conversion. 

Preserving and caring for steam engines is our passion. Check out our website to see how Strasburg Mechanical Services’ expertise can help with your project. 


The Evolution & History of Steam Locomotives

One of the most important inventions of the modern age is the steam locomotive. It helped the United States become an industrialized, global force by allowing for the country’s expansion both geographically and economically.

After briefly discussing the history of steam locomotives, we’ll discuss how the steam locomotive changed society’s thoughts on travel, and how the steam engine is still used today.

Strasburg Railroad train running on the tracks

What is a Steam Locomotive?

The steam locomotive is a self-propelled vehicle, primarily used to pull unpowered cars hauling passengers or goods along tracks made of iron or steel rails. It consists of a boiler to produce steam at high pressures, usually two steam engines that convert the steam into mechanical work, and a running gear.

The running gear consists of a frame, wheels, axles, bearings, spring rigging (suspension system), and driving rods that convert the work of the engines into a rolling motion to move along the tracks. A steam locomotive carries its water supply for generating steam and coal, oil, or wood for heating the boiler.

A Brief History of Steam Locomotives

The history of steam locomotives can’t be talked about without mentioning the history of the steam engine, which is older than most people realize.

The steam engine originated from the aeolipile, designed by Heron of Alexandria in the Second Century B.C. An aeolipile was an apparatus that consisted essentially of a closed vessel (such as a globe or cylinder) with one or more protruding bent tubes out of it, where steam is made to pass from the vessel. The action of the steam jets causes it to revolve.

In the 1690s, Thomas Savery patented a pump with hand-operated valves to raise water from mines by suction produced by condensing steam.

Thomas Newcomen invented an effective and practical steam engine in the early 1710s. The steam engine he designed was similar to Savery’s design and consisted of a piston and cylinder arrangement coupled to a pump through a rocking beam.; used coal

James Watt improved the Newcomen engine in 1765 by adding a separate condenser to avoid heating and cooling the cylinder with each stroke. Then Watt developed a new engine that rotated a shaft.

An early steam carriage, which was ultimately cumbersome, was designed for roads in France by Nicholas-Joseph Cugnot as early as 1769. The first practical steam railway locomotive that pulled carriages was introduced by Richard Trevithick in 1804.

The adaptation of the steam engine to railways became a commercial success with English engineer George Stephenson’s The Rocket in 1829. In America, the first successful steam locomotive was the Tom Thumb, which was built in 1827. It was used by the Baltimore & Ohio Railroad and weighed five tons.

Steam locomotives were mainly used for railroad motive power until WWII. Then the focus shifted to electricity and diesel engines to power locomotives.

Steam locomotives increased rapidly in size and power, but the essential principles remained the same throughout their evolution. Early locomotives were developed through trial and error.

By the time steam locomotives were replaced by newer technologies, they had developed into highly refined machines, designed through scientific research and complex engineering.

What Were the Effects of Steam Locomotives?

Before the steam locomotive, most people didn’t travel past the borders of the state they were born in, much less move across the country. With the invention and adoption of the steam locomotive, society became mobile and pursued opportunities that had been out of reach.

How Did the Steam Locomotive Change Trade?

Steam locomotives made travel and transportation easier and faster. Steam locomotives could be operated year-round in nearly every climate. They allowed the country to expand into distant and remote territories.

It allowed for the development of suburban areas, where people could commute to urban centers for work from more rural areas.

Railroads provided jobs for:

  • Workers building tracks.
  • Conductors and brakemen to direct and assist with making up and moving trains.
  • Engineers and firemen drive the trains and fuel the fires that gave them power.
  • Manufacturing jobs building the locomotives and the cars they pulled, rails and other parts of the track structure, production of the raw materials, and the machines that made these things possible.
  • Train station workers including ticket takers, schedulers, and porters.

Steam locomotives helped businesses move goods across the country quicker, resulting in higher profits and markets expanded. Farmers could move their goods to different locations before the products would spoil.

How Did The Steam Locomotive Change Transportation In America?

Steam locomotives changed not only how people were transported but how people thought about transportation. 

Having an easier mode of transportation changed how people thought about vacations, which had been initially something only the wealthy could afford. With the adoption of the steam locomotive, trains could allow for weekend vacations or day trips to places like beach-side resorts or cities like Atlantic City. 

Railroad operation created the need for standardized time and time zones. Every city or town had train stations and clocks but all had different time standards. Trains needed to be on the same time and schedule so there weren’t any collisions. 

People needed to know what time trains were coming through so they could board the trains.

What Changes Have Been Made?

Though the basic design of the steam locomotive remained mostly unchanged for over a century, many technological improvements were made to their design and construction that improved reliability, efficiency, and performance


Improvements in manufacturing technology allowed for steam locomotives and parts to grow in size as larger machines, cranes, and factory buildings were built. By the end of the steam era, the most powerful locomotives in operation had more pulling power than over 200 of the earliest steam locomotives combined. 

Stronger, lighter-weight materials were used to ensure parts did not grow in weight as they grew in size, allowing larger, more powerful locomotives to operate on existing track structures.

Efficiency & Performance 

Efficiency and performance were increased by improving key components and by adding accessories. The principles of thermal and fluid dynamics became better understood and applied.

Boilers were improved to burn less fuel relative to the amount of steam produced while increasing in size to generate more power overall. Cylinders and steam passages were designed to allow steam to flow into and out of the engines freely. Freer breathing engines could use less steam to produce a greater power output. 

Accessories like superheaters and feedwater heaters recycled heat energy that would typically be wasted to capture more energy from the fuel being burned. 

Mechanical stokers replaced manual shoveling of coal and could feed much more fuel than a human could without breaks. Incorporating oil as a fuel also improved efficiency, providing the opportunity to turn on and turn off the fire as needed.

Stronger Materials

Reliability was improved by the incorporation of new, stronger materials and by using new technologies. 

Steel began to replace wrought and cast iron parts due to its increased strength-to-weight ratio. Steel parts were less prone to breakage and reduced the need for some repairs. Roller bearings replaced older, plain-style bearings, and could run for longer periods without servicing. Plus they were less prone to damage. 

Automatic lubrication systems allowed locomotives to run for longer distances at higher speeds without stopping.

Is the Steam Engine Used Today?

Steam locomotives ultimately fell out of favor due to diesel and electrical engines.  Steam locomotives are 5-7% thermally efficient while diesel locomotives are 30-40% efficient, meaning the steam locomotive needs to burn 6 to 8 times more fuel to do the same amount of work.

Steam locomotives are primarily operated as novelties at this time and are unlikely to make a comeback. You can visit them and learn about the history of steam locomotives at heritage centers, like Strasburg Rail Road. Strasburg Rail Road also offers many rides and experiences on an authentic steam locomotive. 

Over the 100-plus years of their evolution, the steam locomotive began as an individual, small prototype with completely open cabs, tiny boilers, and lesser pulling power, and evolved into a refined machine with tremendous power, having standard design features and built in large numbers.

At Strasburg Rail Road Mechanical Services, we are dedicated to preserving these pieces of history for future generations. With over 250 years of combined experience, our experts are equipped with the tools to save these locomotives and restore them to their former glory. They can also fabricate parts that aren’t made anymore.

Strasburg Rail Road Mechanical Services is dedicated to the maintenance and restoration of steam locomotives. Our workshop and highly-trained experts provide the utmost care and professionalism to all projects. Contact us to see how Strasburg Mechanical Services can assist with your project.