The "GMD1" Locomotives: Specs, Roster, History

Published: August 12, 2024

The GMD1, based from the popular SW1200, is a versatile and distinctive light road-switcher manufactured by EMD's Canadian division, General Motors Diesel (GMD).

Introduced in the late 1950s, the GMD1 was designed to cater to the unique needs of Canadian railroads, particularly for secondary service across Canadian National's many agricultural branch lines across the prairie.

While the model was never sold in the U.S. its design and performance characteristics nevertheless has made the GMD1 a noteworthy model in the history of first-generation diesels.

Canadian National #1073 is at Calgary, Alberta on May 27, 1984, with A1A flexicoils and truck mounted sandboxes (visible next to the stairwell). Doug Kroll photo.

Historical Context and Development

The GMD1 was first introduced in 1958 during a period when many North American railroads were transitioning from steam to diesel power.

Canadian railroads, with their extensive network of lighter branch lines, required a locomotive that could operate efficiently on lighter rail and tighter curves, typical of secondary lines. GMD, leveraging its knowledge from EMD's very successful GP7 and GP9 in the U.S., developed the GMD1 to meet these specific requirements.

Design and Specifications

The GMD1 was first introduced in 1958 during a period when many North American Class 1s throughout the U.S. and Canada were completing the transition from steam to diesel power.

The design is essentially an SW1200 wrapped in a road-switcher carbody. It is easily recognizable by its wide-vision cab windows, offset raised cab, and general boxy appearance.

The model is equipped with the 567C power plant and a Roots-type supercharged prime mover. The 567 was renowned for its reliability and performance, also powering early first generation models like the F3, F7, GP7, GP9, SD9, and GP30 in their 16-cylinder configurations.

Canadian railroads, with their extensive network of lighter agriculutral branch lines, required a locomotive that could operate efficiently on lighter rail and tighter curves. GMD, leveraging its knowledge from EMD's successful Geeps (GP7 and GP9) in the U.S. during the 1950s, developed the GMD1 to meet these specific requirements.

**1. General Characteristics:**

- **Power Type:** Diesel-electric

- **Builder:** General Motors Diesel (GMD)

- **Production Dates:** 1958–1960

- **Total Units Produced:** 101

**2. Prime Mover and Engine:**

- **Engine:** EMD 567C

- **Cylinders:** 12

- **Power Output:** Originally 1,200 horsepower, later models upgraded to 1,350 horsepower

**3. Wheel Arrangement:**

- **Standard Configuration:** A1A-A1A

- This unique wheel arrangement featured two powered axles and one idler axle per truck, distributing the locomotive's weight more evenly and reducing axle loads, which was advantageous for lighter track conditions.

- **Modified Configuration:** Units were built in either an A1A-A1A or B-B wheel arrangement.

GMD1 (A1A-A1A): Canadian National #1000-1077; Northern Alberta #301-305; and Northern Alberta #311-312 (ex-CN #1072 and #1077).

GMD1 (B-B): Canadian National #1900-1917 (only GMD1s equipped with steam generators).

**4. Dimensions and Weight:**

- **Length:** Approximately 54 feet, 9 inches

- **Weight:** Depending on configuration, around 240,000 pounds

Operational Use

The GMD1 was specifically designed to be highly adaptable, making it suitable for both branch line service and light mainline duties. Its flexibility was a significant asset, allowing it to be used in various roles, including:

1. **Freight Service:** The primary role of the GMD1 was in freight operations. Its relatively lightweight and flexible wheel arrangement allowed it to efficiently haul trains on secondary lines where track conditions could not support heavier locomotives.

2. **Yard Switching:** The locomotive's versatility also made it valuable in yard switching duties. Its robust engine and flexible design allowed it to handle a variety of tasks within rail yards efficiently.

3. **Passenger Service:** Canadian National units #1900-1917 were equipped with B-B trucks and steam generators for light passenger assignments.

Complete Data Sheet

Specification	Details
Engine Builder	GMD/EMD
Engine	567C (12 cylinder)
Bore & Stroke	8.5" X 10"
RPM (Maximum / Minimum)	800 / 275
Main Generator	GM - D15C
Horsepower	1200
Gear Ratios	62:15 (A1A-A1A), 58:19 (B-B)
Speed	65-83 mph
Configuration	A1A-A1A or B-B
Weight	239,000 lbs (A1A-A1A) or 246,000 (B-B)
Traction Motors	GM D47B (6)
Tractive Effort (Starting)	73,700 lbs @ 25%
Tractive Effort (Continuous)	30,000 lbs @ 9.3 mph
Multiple Unit Capability	Yes
Dynamic Braking	No
Auxiliary Generator	GM
Alternator	A8102A1
Air Brake	Westinghouse (6SL)
Compressor	Gardner-Denver (WBO)
Exterior Dimensions
Total Length	54' 9"
Wheel Diameter	40"
Truck Wheel Base	A1A-A1A (10' 0"): B-B (8' 06")
Height to Top Engine Hood	12' 8 ½"
Height to Top Cab	15' 4"
Cab Width	10' 3"
Top of Walkway	7' 6"
Walkway Width	4' 7 ½"
Engine Hood Width	10' 0"
Center Bolster	31' 0"
Center Front Truck to Front Pilot	2' 3"
Center Rear Truck to Rear Pilot	2' 3"
Distance between Truck Centers	A1A-A1A (41' 6"): B-B (39' 0")
Minimum Turning Radius	39 degrees
Capacities
Fuel Oil	1009 Gallons
Lubricating Oil	137 Gallons
Engine Cooling Water	785 Gallons
Sand Capacity	28 cubic feet
Options
Vapor-Clarkson Boiler	Model OK-4625

Production Roster

Owner	Road Number	Serial Number	Order Number	Completion Date
Canadian National	1000-1028	A1420-A1448	C244	8/1958-10/1958
Canadian National	1900	A1449	C245	9/1958
Canadian National	1901-1917	A1575-A1591	C254	11/1958-1/1959
Canadian National	1029-1033	A1592-A1596	C255	1/1959
Canadian National	1034-1049	A1697-A1712	C258	2/1959-3/1959
Canadian National	1050-1067	A1747-A1764	C262	10/1959-11/1959
Northern Alberta	301-305	A1829-A1833	C270	12/1959
Canadian National	1068-1077	A1883-A1892	C274	4/1960

Preservation

The GMD1 remains a noteworthy model in the annals of Canadian railroading due to its unique design and operational flexibility. While most units have been retired due to advancing technology and changing operational needs, a few have been preserved and remain in operation:

1. **Canadian National Railway (CN):** The primary operator of the GMD1, CN, used these locomotives extensively across its vast network. Although all have been retired, CN’s use of the GMD1 underscored its reliability and adaptability.

2. **Preservation:** Notably, in 2010, the Portland, Oregon-based Oregon Pacific Railroad acquired Canadian National GMD1 #1413, assigning it to the East Portland Line.

This unit is occasionally deployed across other Oregon Pacific properties and has recently been spotted in operation at the Progressive Rail property at the Clackamas Valley Railway, servicing the industrial park adjacent to the Union Pacific mainline.

Other preserved GMD1 units include one with Oregon Pacific, two with the Waterloo Central Railway, twenty in Cuba, and three with Cando Rail Services in Canada.

Legacy

With the advent of newer locomotives, the need for GMD1s at CN gradually diminished until they were eventually phased out. Of the 101 units built, the last was retired by CN in 2021 and now operates on Ontario’s Waterloo Central Railway.

Once a distinctive presence traversing Canada’s remote regions, the GMD1 locomotives continue to make significant contributions to modern railroading today.

The model stands as a testament to General Motors Diesel's capacity for innovation and its commitment to meeting the specific needs of the Canadian railway market.

With its unique A1A-A1A wheel arrangement, adaptability for both freight and passenger services, and significant operational flexibility, the GMD1 carved out an important niche in the history of North American railroading.

Its legacy continues through preserved units and the memories of the railroads and crews who relied on its dependable performance across the challenging terrains of Canada's branch lines and light-duty mainlines.