Did the One & Only PRR 6-8-6 S2 Steam Turbine Locomotive Live Up to the Hype?

Take a trip down memory lane as we explore the history of the infamous 6-8-6 S2 steam turbine locomotive…and its modern-day HO scale counterparts.

Imagine my excitement as I was unpacking a vintage brass locomotive recently when I found an old Baldwin Locomotive brochure promoting their infamous 6-8-6 S2 steam turbine locomotive, built for the Pennsylvania Railroad.

Join me as I delve into the history of this fascinating steam locomotive, once considered a way to continue the dominance of steam through the integration of technology that was then in widespread use in the marine industry.

The 6-8-6: An Alternative to Diesel Power? Maybe not.

Constructed in a joint effort by Baldwin Locomotive Works and Westinghouse Electric & Manufacturing, the S2 wins the title of one and only: #6200 was the sole locomotive built, and was the lone example of the 6-8-6 wheel arrangement.

As diesel began to take over the railways, many attempts were made at producing an alternative to diesel power, mostly to no avail.

“For the first time a way has been found to put into a locomotive the same kind of power that sends big battleships forward – turbine drive!” boasts a 1945 issue of Trains magazine. Further, “No bigger than your electric refrigerator, the steam turbine itself can produce power to pull the heaviest loads at high speeds. And the engineman controls the whole operations with a single small lever which works like a gear-shift on an automobile!”

We glimpse the futuristic (and perhaps, overly confident) mindset of the era, “One of the most important changes in the power of principle of the steam locomotive in over 100 years, the turbine drive engine gives promise of a great future in the field of train transportation.”

5 Fast Facts on the PRR S2 6-8-6 Locomotive:

#1 – The PRR S2 steam turbine locomotive was delivered in September 1944 and retired just about 8 years later, in January 1952.

#2 – The Pennsylvania S2 has an impressive boast: it was the biggest, heaviest and fastest direct-drive turbine locomotive design of all time.

#3 – It used a direct-drive steam turbine from the Westinghouse Electric & Manufacturing Company which was geared to the center pair of axles, with the outer two axles connected by side rods.

#4 – With a fixed gear ratio of 18.5:1, the intention of the S2’s design was to avert energy loss. It reached a mechanical efficiency of 97%.

#5 – The S2 was supposed to be a 4-8-4…until WWII-era wartime restrictions on the use of lighter steel alloys prompted the deployment of heavier alloys. This tipped the scales, and the S2 required bigger leading and trailing trucks.

BONUS fun fact: The S2 originally didn’t have a smoke deflector when it was delivered to the Pennsylvania Railroad in 1944. That was until the PRR soon discovered that the locomotive blew heavy smoke at lower speeds.

The solution was a bit convoluted: a pair of small smoke deflectors was developed, and a slim semi-circular metal plate for smoke lifting was filled behind the smokestack. But, when these were found to be insufficient, an interesting, substantially bigger pair of “elephant ears” were implemented instead.

Excerpts from the Baldwin Locomotive Works Catalog

BALDWIN – Westinghouse




Reprinted by ALCO Models

P.O. Box 211, Port Jefferson, New York 11777

Courtesy Baldwin-Lima-Hamilton Corp.

 “A high-speed locomotive powered by a steam turbine, like those that drive the nation’s new giant battleships and swift destroyers, has been built to speed wartime and peacetime traffic on the Pennsylvania Railroad.

The new coal-burning locomotive is propelled by jets of steam spinning a precision-made “wind-maill” encased in steel. With a rating of 6,500 horsepower, the new “iron horse” will be able to maintain the schedules of the largest and heaviest passenger trains.”


Two pioneers in the railroad equipment field pooled their experience and facilities in the building of this turbine locomotive, first of its type to be produced in the United States. The locomotive was built at the Eddystone Plant of the Baldwin Locomotive Works and the turbines and gears were manufactured by Westinghouse Electric and Manufacturing Company which has wide experience in building marine turbines and gears to propel United States warships and cargo vessels.

This new step in railroading was undertaken with the immediate aim of trying out the turbine principle in practical operation, to determine its adaptability in opening the way to higher speeds and greater operating efficiency for the steam locomotive.

The boiler, frame, trucks and driving wheels are of the conventional type, the most notable difference being the absence of cylinders, valve motion and their accompanying parts.

The use of a turbine drive eliminates piston rods and other reciprocating parts and, therefore, the driving wheels can be perfectly balanced. This permits operating the wheels at higher speeds than would be practical with a locomotive of the conventional type. Driving wheels can be made materially smaller, leaving more space for fire-box and boiler.


Due to its turbine drive, the locomotive has uniform torque at all speeds, similar to that of electric and diesel-electric locomotives. The tractive power of the turbine locomotive, exerted at the rail, exceeds at practically all speeds that of a conventional steam locomotive having equal boiler capacity and weight on rivers. It also exceeds the tractive force of a 6,000 hp diesel-electric locomotive at speeds above 40 miles per hour, with a considerable advantage at speeds above 50 miles per hour.

At speeds above 30 miles per hour the steam consumption of the turbine locomotive per horse-power at the rail is considerably less than that of a comparable reciprocating steam locomotive. At starting and at very low speeds the steam consumption of the turbine is relatively high, but with modern high-speed, main-line schedules, with few stops and very little operation at low speeds, this is more than compensated for by the advantages of the turbine at high speeds.

The 6-8-6 S2 Locomotive Lives on…in HO Scale

From O to HO scale, the 6-8-6 turbine steam loco lives on. The ever-popular Broadway Limited offered several HO scale versions more recently, including the following with their Paragon4 DC/DCC sound system:

  1. 6184 PRR S2 6-8-6 Turbine #6200, as-built version
  2. 6185 PRR S2 6-8-6 Turbine #6200, with small smoke deflectors
  3. 6186 PRR S2 6-8-6 Turbine #6200, with large smoke deflectors
  4. 6187 PRR S2 6-8-6 Turbine, Unlettered, with large smoke deflectors, Painted Brass
  5. 6188 PRR S2 6-8-6 Turbine #6200, with large smoke deflectors, Tuscan Red w/ 5-Stripes

These HO scale models of the 6-8-6 steam locomotive offer Broadway Limited’s older Paragon3 DC/DCC sound:

  1. 2694 PRR S2 6-8-6 Turbine #6200, as-delivered version
  2. 2695 PRR S2 6-8-6 Turbine #6200, with small smoke deflectors
  3. 2696 PRR S2 6-8-6 Turbine #6200, with large smoke deflectors

See what Broadway Limited HO scale locomotives we have in stock & ready to ship to you today. Or, check out our curated selection of steam locomotives.