British Rail Class 35

British Rail Class 35

British Railways Hymek Class 35 D7017 at Washford on the West Somerset Railway

Type and origin Power type Diesel-hydraulic Builder Beyer Peacock (Hymek) Ltd Serial number 7894–7938, 7949–8004 Build date 1961–1964 Total produced 101

Specifications AAR wheel arr. B-B UIC class B'B' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 9 in (1.143 m) Wheelbase 36 ft 0 in (10.97 m) Length 51 ft 8 1⁄2 in (15.761 m) Width 8 ft 10 in (2.69 m) Height 12 ft 10 in (3.91 m) Loco weight 75 long tons (76.2 t; 84.0 short tons) Fuel capacity 800 imp gal (3,600 l; 960 US gal) Prime mover Bristol-Siddeley / Maybach MD870 Engine type V16 Diesel Displacement 86 L (5,200 cu in) Cylinders 16 Transmission Hydraulic, Stone-Maybach Mekydro type K184U MU working Yellow Triangle Train heating Steam Train brakes Vacuum

Performance figures Maximum speed 90 mph (145 km/h) Power output Engine: 1,700 bhp (1,270 kW) at 1500 rpm Tractive effort Maximum: 46,600 lbf (207.3 kN) Continuous: 33,950 lbf (151.0 kN)@ 12.5 mph (20.1 km/h) Loco brakeforce 57 long tons-force (568 kN)

Career Operators British Railways Numbers D7000–D7100 Nicknames Hymek Axle load class Route availability 6 Retired 1971–1975 Preserved four preserved, remainder scrapped

Specifications
AAR wheel arr.	B-B
UIC class	B'B'
Gauge	4 ft 8 1⁄2 in (1,435 mm) standard gauge
Wheel diameter	3 ft 9 in (1.143 m)
Wheelbase	36 ft 0 in (10.97 m)
Length	51 ft 8 1⁄2 in (15.761 m)
Width	8 ft 10 in (2.69 m)
Height	12 ft 10 in (3.91 m)
Loco weight	75 long tons (76.2 t; 84.0 short tons)
Fuel capacity	800 imp gal (3,600 l; 960 US gal)
Prime mover	Bristol-Siddeley / Maybach MD870
Engine type	V16 Diesel
Displacement	86 L (5,200 cu in)
Cylinders	16
Transmission	Hydraulic, Stone-Maybach Mekydro type K184U
MU working	Yellow Triangle
Train heating	Steam
Train brakes	Vacuum

The British Rail (BR) Class 35 is a class of mixed-traffic B-B diesel locomotive with hydraulic transmission. Because of their Mekydro-design hydraulic transmission units, the locomotives became known as the Hymeks.

The class was developed for the Western Region of British Railways, which had opted for lightweight locomotives with hydraulic transmission, when allocated funds under the British Railways Modernisation Plan of 1955. One hundred and one of the class were built between 1961 and 1964, when it became apparent that there was a requirement for a medium power diesel-hydraulic design for both secondary passenger work and freight duties.

They were allocated to Bristol Bath Road, Cardiff Canton, and Old Oak Common. None of the class was named. Withdrawal from service began in 1971, and was completed by 1975. Their early withdrawal was caused, primarily, by BR classifying the hydraulic transmission as non-standard. Four examples survived into preservation.

The builder, Beyer Peacock (Hymek) Ltd, was a joint venture between Bristol Siddeley Engines (BSE) (licensed to build Maybach engines), Stone-Platt Industries (licensed to build Mekydro transmissions), and the locomotive manufacturer Beyer, Peacock and Company. At the time they were built, the Hymeks were the most powerful diesel-hydraulic locomotives operating with a single engine - the Maybach MD870. Unlike the higher-powered diesel-hydraulic Warship and Western locomotives in the Western Region fleet (with dual Maybach MD655 engines), the Hymeks were not based on an existing West German design.

When first built, the Hymeks were given a more elaborate livery than many of the contemporary British Railways diesel classes. The main body of the locomotive was the standard dark Brunswick green, but with a lime green stripe along the bottom of the bodywork. The roof was medium grey, and the finishing touch was to paint the window surrounds in ivory white. In the early 1960s, yellow warning panels were added to the lower part of the front ends, in accordance with BR's then-new policy. Following the corporate identity campaign and the change of name to British Rail plus introduction of the "double arrow" logo in 1964, some locomotives received all-over BR Rail blue with small yellow warning panels. This was quickly changed by the return of off-white window surrounds. The final variation was BR blue with full yellow ends, the yellow being extended around the cab side windows.