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South African Class 16A 4-6-2

South African Class 16A 4-6-2
SAR Class 16A 852 (4-6-2) a.jpg
No. 852, Braamfontein, Johannesburg, June 1936
Type and origin
Power type Steam
Designer South African Railways
(D.A. Hendrie)
Builder North British Locomotive Company
Serial number 20956-20957
Model Class 16A
Build date 1915
Total produced 2
Specifications
Configuration 4-6-2 (Pacific)
Driver 1st coupled axle (Inner cylinders)
2nd coupled axle (Outer cylinders)
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia. 30 in (762 mm)
Coupled dia. 60 in (1,524 mm)
Trailing dia. 33 in (838 mm)
Tender wheels 34 in (864 mm)
Wheelbase 57 ft 7 14 in (17,558 mm)
 • Engine 31 ft 1 in (9,474 mm)
 • Leading 6 ft 2 in (1,880 mm)
 • Coupled 10 ft 9 in (3,277 mm)
 • Tender 16 ft 9 in (5,105 mm)
 • Tender bogie 4 ft 7 in (1,397 mm)
Length:
 • Over couplers 65 ft 11 58 in (20,107 mm)
Height 12 ft 10 in (3,912 mm)
Axle load 16 LT 18 cwt (17,170 kg)
 • Leading 16 LT 8 cwt (16,660 kg)
 • Coupled 16 LT 18 cwt (17,170 kg)
 • Trailing 14 LT (14,220 kg)
 • Tender bogie 27 LT 10 cwt (27,940 kg)
Bogie 2: 23 LT 11 cwt (23,930 kg)
 • Tender axle 13 LT 15 cwt (13,970 kg)
Adhesive weight 50 LT 14 cwt (51,510 kg)
Loco weight 81 LT 2 cwt (82,400 kg)
Tender weight 51 LT 1 cwt (51,870 kg)
Total weight 132 LT 3 cwt (134,300 kg)
Tender type MP1 (2-axle bogies)
MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted
Fuel type Coal
Fuel capacity 10 LT (10.2 t)
Water cap 4,250 imp gal (19,300 l)
Firebox type Belpaire
 • Firegrate area 36 sq ft (3.3 m2)
Boiler:
 • Pitch 7 ft 9 in (2,362 mm)
 • Diameter 5 ft 1 58 in (1,565 mm)
 • Tube plates 19 ft 9 in (6,020 mm)
 • Small tubes 119: 2 14 in (57 mm)
 • Large tubes 21: 5 12 in (140 mm)
Boiler pressure 200 psi (1,379 kPa)
Safety valve Ramsbottom
Heating surface 2,121.5 sq ft (197.09 m2)
 • Tubes 1,975.5 sq ft (183.53 m2)
 • Firebox 146 sq ft (13.6 m2)
Superheater:
 • Heating area 459.5 sq ft (42.69 m2)
Cylinders Four
Cylinder size 14 in (356 mm) bore
26 in (660 mm) stroke
Valve gear Walschaerts
Valve type Piston
Couplers Johnston link-and-pin
AAR knuckle (1930s)
Performance figures
Tractive effort 25,480 lbf (113.3 kN) @ 75%
Career
Operators South African Railways
Class Class 16A
Number in class 2
Numbers 851-852
Delivered 1915
First run 1915
Withdrawn 1944
The 2nd coupled axle had flangeless wheels
Type and origin
Power type Steam
Designer South African Railways
(D.A. Hendrie)
Builder North British Locomotive Company
Serial number 20956-20957
Model Class 16A
Build date 1915
Total produced 2
Specifications
Configuration 4-6-2 (Pacific)
Driver 1st coupled axle (Inner cylinders)
2nd coupled axle (Outer cylinders)
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia. 30 in (762 mm)
Coupled dia. 60 in (1,524 mm)
Trailing dia. 33 in (838 mm)
Tender wheels 34 in (864 mm)
Wheelbase 57 ft 7 14 in (17,558 mm)
 • Engine 31 ft 1 in (9,474 mm)
 • Leading 6 ft 2 in (1,880 mm)
 • Coupled 10 ft 9 in (3,277 mm)
 • Tender 16 ft 9 in (5,105 mm)
 • Tender bogie 4 ft 7 in (1,397 mm)
Length:
 • Over couplers 65 ft 11 58 in (20,107 mm)
Height 12 ft 10 in (3,912 mm)
Axle load 16 LT 18 cwt (17,170 kg)
 • Leading 16 LT 8 cwt (16,660 kg)
 • Coupled 16 LT 18 cwt (17,170 kg)
 • Trailing 14 LT (14,220 kg)
 • Tender bogie 27 LT 10 cwt (27,940 kg)
Bogie 2: 23 LT 11 cwt (23,930 kg)
 • Tender axle 13 LT 15 cwt (13,970 kg)
Adhesive weight 50 LT 14 cwt (51,510 kg)
Loco weight 81 LT 2 cwt (82,400 kg)
Tender weight 51 LT 1 cwt (51,870 kg)
Total weight 132 LT 3 cwt (134,300 kg)
Tender type MP1 (2-axle bogies)
MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted
Fuel type Coal
Fuel capacity 10 LT (10.2 t)
Water cap 4,250 imp gal (19,300 l)
Firebox type Belpaire
 • Firegrate area 36 sq ft (3.3 m2)
Boiler:
 • Pitch 7 ft 9 in (2,362 mm)
 • Diameter 5 ft 1 58 in (1,565 mm)
 • Tube plates 19 ft 9 in (6,020 mm)
 • Small tubes 119: 2 14 in (57 mm)
 • Large tubes 21: 5 12 in (140 mm)
Boiler pressure 200 psi (1,379 kPa)
Safety valve Ramsbottom
Heating surface 2,121.5 sq ft (197.09 m2)
 • Tubes 1,975.5 sq ft (183.53 m2)
 • Firebox 146 sq ft (13.6 m2)
Superheater:
 • Heating area 459.5 sq ft (42.69 m2)
Cylinders Four
Cylinder size 14 in (356 mm) bore
26 in (660 mm) stroke
Valve gear Walschaerts
Valve type Piston
Couplers Johnston link-and-pin
AAR knuckle (1930s)
Performance figures
Tractive effort 25,480 lbf (113.3 kN) @ 75%
Career
Operators South African Railways
Class Class 16A
Number in class 2
Numbers 851-852
Delivered 1915
First run 1915
Withdrawn 1944

The South African Railways Class 16A 4-6-2 of 1915 was a steam locomotive.

In 1915, the South African Railways placed two experimental four-cylinder simple expansion steam locomotives with a 4-6-2 Pacific type wheel arrangement in passenger train service. They were designated Class 16A.

The Class 16A 4-6-2 Pacific type locomotive was designed by D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922, and was built in 1915 by the North British Locomotive Company (NBL) in Glasgow, Scotland. Two locomotives were delivered in November 1915, numbered 851 and 852.

Except that they had four cylinders instead of the usual two, they were identical in most respects to their predecessors, the Class 16, which were delivered by NBL a year earlier. They were also superheated, with Walschaerts valve gear and Belpaire fireboxes, and were also delivered with Type MP1 tenders with a 10 long tons (10.2 tonnes) coal capacity and a 4,250 imperial gallons (19,300 litres) water capacity.

With the Class 16A, Hendrie experimented with four-cylinder simple expansion (simplex) steam power. All four cylinders were arranged in line below the smokebox. The Walschaerts valve gear had rocker arms attached to the tail ends of the outer piston valves which passed through the frames and then actuated the adjacent inner piston's valves. It operated in the simplex configuration, whereby steam is fed directly to all four cylinders and spent steam is exhausted by all cylinders directly through the smokebox and up the chimney.

All four cylinders were the same size, with a 14 inches (356 millimetres) bore and 26 inches (660 millimetres) stroke, which presented a number of problems which had to be overcome to arrange two of these in the limited space between the frames. The outer cylinders drove the centre pair of coupled wheels, while the inner cylinders operated on a cranked leading coupled wheel axle. Each inside crank was arranged at an angle of 180 degrees with its adjacent outside crank.

The arrangement made for a very smooth-running locomotive capable of very fast running since the shouldering effect which occurs on two-cylinder locomotives was completely absent. They were very popular with their crews because of their smooth and steady running.


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