The British Railways Class 129 was a class of single-car Diesel Multiple Unit (DMU) built in 1955 for British Railways. 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, which were also built by Cravens.
Service[]
They were given the yellow diamond coupling code as they were intended to work in West Cumberland with the yellow diamond Derby Lightweight sets. However, in the two and a half years between ordering and delivery plans changed and only one would make it to the Carlisle area. They were used for parcel services in West Cumberland.
Withdrawal[]
The first to be withdrawn was 55998 in December 1972, possibly due to fire damage, the other two were withdrawn in October 1973 for being non-standard. They were replaced by three Western Regio Class 128s (55993-5) arriving at Chester from Tyseley.
Departmental use[]
In 1975, the first unit (M55997) was converted as a test bed for hydrostatic drive. It was renumbered RDB 975385 and named Laboratory 9 ‘Hydra’.
It was fitted hydrostatic transmission having the normal Leyland 680 six cylinder engine driving two 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The unit was withdrawn in January 1986 and scrapped in August that year by Vic Berry at Leicester.