Canadian National Class Z-4-a

The Canadian National Class Z-4-a was a batch of nine electric "boxcab" type locomotives built by English Electric for the Montreal Harbour Commissioners, later National Harbour Board of Canada from 1924 to 1926. The Port of Montreal decided to de-electrify its railway system in 1940, and so in 1941 the fleet of locomotives were traded with Canadian National Railway for seven steam switcher locomotives. They were given the classification Class Z-4-a by CN and renumbered. They would subsequently be renumbered in 1949 and finally 1969. Here they complimented the older GE built boxcabs, the class Z-1-a. Both boxcab types served the Mount Royal Tunnel route in Montreal for many years until retirement in June 1995.

Canadian National Class Z-4-a
#6722 at Monkland Station, Montreal 1971
Type and origin Power type Electric Designer English Electric Builder English Electric Build date 1924-26 Total produced 9
Specifications Configuration: ​  • AAR B+B  • UIC Bo+Bo Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Minimum curve 264 ft (80 m) Loco weight 201,600 lb (91,444 kg) (78.925 t; 77.679 LT; 87.000 ST) Electric system/s 2400, later 3000 V DC catenary Current pickup(s) Pantograph
Performance figures Maximum speed 50 mph (80 km/h) Power output: ​  • 1 hour 1,720 hp (1,280 kW) Tractive effort: ​  • Starting 50,400 lbf (224 kN)  • Continuous 21,400 lbf (95 kN)
Career Operators Montreal Harbour Commissioners National Harbour Board Canadian National Railway Class Z-4-a Number in class 9 Numbers 101-109 (1924 to 1941) 9180-9189 (1941 to 1949) 180-188 (1949 to 1969) 6716-6724 (1969 to withdrawal) Withdrawn 1995 Disposition All scrapped

See also

• CN electric multiple unit Multiple unit sets used in the Mt Royal Tunnel
• Canadian National Class Z-1-a earlier Mt Royal Tunnel boxcabs built by General Electric
• NZR EO class (1923) smaller locomotives built for New Zealand in the same era