The "RS18": MLW's Popular Road-Switcher

Published: August 12, 2024

By: Adam Burns

The RS18, produced by the Montreal Locomotive Works (MLW), was a very successful design that left a significant mark on Canadian railroading.

Based from Alco's RS11 in the U.S., the RS18 was built between 1956-1968 and part of the Road Switcher (RS) series. While the model was generally designed for freight service it was also offered with an optional steam generator for passenger assignments.

Known for its versatility, robust performance, and adaptability, the RS18 was regarded as one of the most reliable designs during its many years in service.  MLW ultimately sold some 351 units during a twelve year production run.  

CP Rail (Canadian Pacific) RS18 #8783 lays over at Saint-Luc, Quebec in September, 1976. Warren Calloway photo.

Historical Context and Development

The RS18 first entered MLW's catalog the end of the transition from steam to diesel locomotives. Railroads were seeking reliable, powerful, and multipurpose locomotives that could handle varying operational demands.

The Montreal Locomotive Works responded to this demand with the RS18, positioning it as a successor to the earlier RS10 model.

Interestingly, MLW designs were generally better received and enjoyed longer service lives in Canada than their Alco counterparts.   For example, one could still find RS18s, C424s, and M630s in regular service throughout Canada through the mid-1990s when similar Alco designs in the States had long since disappeared from Class 1 rosters by the early 1980s.

MLW built some 351 units of the RS18. The design improvements and technological advancements from Alco were incorporated into the RS18, ensuring it met the rigorous standards and expectations of the North American railroad industry.

Design and Specifications

In his book, "The Diesel Builders Volume Two: American Locomotive Company and Montreal Locomotive Works," author John Kirkland notes the RS18 was initially referred to as the RS11M before given it's now common moniker, presumably to denote its horsepower rating.

It was nearly identical to the RS11 except for its lack of notches along the upper corners of the high hood, a design feature meant to provide access to the sandbox fillers.

The RS18 could be produced in either a short low, or high hood configuration and was ultimately built in both styles.

**1. Prime Mover and Engine:**

- **Engine:** ALCO 251B
- **Cylinder Configuration:** V12
- **Power Output:** 1,800 horsepower

The RS18 is powered by the Alco 251B prime mover, a V12, four-stroke diesel engine capable of delivering 1,800 horsepower. This engine was renowned for its reliability and performance, enabling the locomotive to handle both freight and passenger services effectively.

**2. Wheel Arrangement:**

- **Configuration:** B-B (four axles, all powered)

**3. Dimensions and Weight:**

- **Length:** 56 feet, 11 ¾ inches

- **Weight:** 232,000 - 247,000 pounds

**4. Notable Features:**

- **Dual-Service Capability:** Canadian National would later modify some of its RS18s with HEP equipment in the short hood for passenger assignments.

Operational Use and Impact

The RS18 quickly became a workhorse for many Canadian railroads, particularly Canadian National and Canadian Pacific, the primary operators of this model. Several factors contributed to its widespread adoption and positive reception:

**1. Reliability and Performance:**

The RS18's robust design and reliable 251B engine made it a dependable locomotive for various types of services. Whether hauling freight trains across long distances or managing passenger services, the RS18 consistently delivered performance.

**2. Versatility:**

The RS18’s dual-service capability allowed it to be utilized in a plethora of roles. 

**3. Ease of Maintenance:**

Operators found the RS18 relatively straightforward to maintain. This ease of maintenance was a crucial factor for railroads seeking to minimize operational downtimes.

**4. Adaptability:**

As operational needs changed, many RS18 units were rebuilt or upgraded to extend their service life (denoted as "RS18u"). This adaptability ensured that the RS18 remained relevant and functional in evolving rail environments.

Notable Operators and Services

**1. Canadian National:**

CN was one of the largest operators of the RS18, acquiring 233 examples, utilizing the locomotive in a variety of roles across its extensive network. From hauling heavy freight trains to passenger service, the RS18 was a versatile asset for CN.

**2. Canadian Pacific:**

CP also employed a significant number of RS18 units - 72 in all - often using them for similar dual-service roles. The reliability and performance of the RS18 made it a valuable addition to CP’s locomotive roster.

**3. Other Operators:**

Although primarily used by CN and CP, the RS18 was also operated by smaller Canadian railroads and private firms including Pacific Great Eastern, Quebec Cartier Mining, Roberval & Saguenay, Arnaud Railway (Wabush Iron),  International Nickel, and Quebec Iron & Titanium.  Its versatility and dependable performance made it a viable option for various rail operations.

Legacy and Preservation

The legacy of the RS18 is cemented by its significant contribution to North American railroading, especially in Canada. While many units have been retired from active service, several have been preserved by railway museums and historical societies, including a handful which have found their way into the U.S.

Specifications

Production Roster

* Pacific Great Eastern #627 was wrecked and rebuilt using Pacific Great Eastern #616's construction number (84819).

Canadian National RS-18 #3153 is seen here at Spadina Street in Toronto on October 11, 1976. This unit illustrates how CN extended the short hood out to the end of the frame, eliminating the walkway, in order to house the HEP engine. Doug Kroll photo.

Legacy

The RS18 stands as a testament to the innovation and adaptability of mid-20th-century locomotive engineering.

Its legacy endures through preserved units in railway museums and the continued use of some locomotives in heritage operations. The RS18 remains a cherished part of railway history, symbolizing a period of technological advancement and operational excellence in the rail industry.