British Rail Class 129

The British Rail Class 129 was a class of single car diesel multiple units (DMU) built in 1955 for British Rail. Only three were built by Cravens and were introduced in 1958. The class was built for parcels traffic like the Class 128. One unit (55997) survived into departmental service being named 'Hydra'. The driving ends of a Class 129 car bore a visible similarity to that of the Class 105, also built by Cravens.

British Rail Class 129
In service	1958–1973
Manufacturer	Cravens
Order no.	30418[1]
Family name	First generation
Replaced	Steam locomotives and carriages
Constructed	1955
Entered service	1958[2]
Scrapped	1975 1986
Number built	3
Number scrapped	All
Formation	Single car: DMLV[2]
Diagram	BR531[1]
Fleet numbers	55997-55999[3]
Capacity	Luggage space only[2]
Operators	British Railways
Depots	Chester Newton Heath[4]
Lines served	London Midland Region
Specifications
Car body construction	Steel
Car length	57 ft 6 in (17.53 m) (over body ends)[1]
Width	9 ft 3 in (2.82 m) (overall)[1]
Height	12 ft 4+1⁄2 in (3.772 m) (over roof)[1]
Doors	Slam[2]
Wheelbase	40 ft 0 in (12.19 m) (bogie centres) 8 ft 6 in (2.59 m) (bogies)[1]
Maximum speed	70 mph (113 km/h)[2]
Weight	30 long tons (30 t; 34 short tons)[1]
Prime mover(s)	2 × BUT (AEC) 150 hp (110 kW)[2][1]
Power output	300 hp (220 kW)[2]
Braking system(s)	Vacuum[2]
Coupling system	Screw[2]
Multiple working	♦ Yellow Diamond
Track gauge	1,435 mm (4 ft 8+1⁄2 in) standard gauge

Fleet list

Table of orders and numbers

Lot No.	Type	Diagram	Qty	Fleet numbers	Notes
30418	Non-ganwayed Motor Parcel Van	531	3	M55997–55999

Departmental Usage

One unit, M55997, was converted as a test bed for hydrostatic drive in 1980, was renumbered RDB 975385, and named Laboratory 9 ‘Hydra’.^[5]

It was fitted hydrostatic transmission having the normal Leyland Motors 680 six-cylinder engine driving two Bosch Rexroth Hydramatic axial piston pumps. Each pump supplied fluid to a Volvo fixed displacement compact axle-end motor which drove the axle directly. The maximum system pressure was in the order of 400 bar (40 MPa; 5,800 psi).

This arrangement was only fitted to one bogie, the other one retaining its normal drive but with the cardan shaft disconnected.

The unit was finally withdrawn in January 1986 and scrapped in August that year by Vic Berry at Leicester.