A rail vehicle having a vehicle frame supported on on-track undercarriages and a hydraulic drive system powered by a motor. The drive system comprises a hydrodynamic drive associated with a first on-track undercarriage as well as a hydrostatic drive associated with a second on-track undercarriage. With the latter is associated a drive pump connected to a drive motor. The motor is designed for a higher power output than is necessary for the operation of the hydrodynamic drive. A pump distribution gear is switched between the motor and the hydrodynamic drive, via which the drive pump of the hydrostatic drive can be connected. This takes place in dependence on a friction value μ between the rail and wheel.

A rail vehicle having a vehicle frame supported on on-track undercarriages and a hydraulic drive system powered by a motor. The drive system comprises a hydrodynamic drive associated with a first on-track undercarriage as well as a hydrostatic drive associated with a second on-track undercarriage. With the latter is associated a drive pump connected to a drive motor. The motor is designed for a higher power output than is necessary for the operation of the hydrodynamic drive. A pump distribution gear is switched between the motor and the hydrodynamic drive, via which the drive pump of the hydrostatic drive can be connected. This takes place in dependence on a friction value μ between the rail and wheel.

A rail vehicle having a vehicle frame supported on on-track undercarriages and a hydraulic drive system powered by a motor. The drive system comprises a hydrodynamic drive associated with a first on-track undercarriage as well as a hydrostatic drive associated with a second on-track undercarriage. With the latter is associated a drive pump connected to a drive motor. The motor is designed for a higher power output than is necessary for the operation of the hydrodynamic drive. A pump distribution gear is switched between the motor and the hydrodynamic drive, via which the drive pump of the hydrostatic drive can be connected. This takes place in dependence on a friction value between the rail and wheel.

A series hydrostatic transmission for a vehicle having a wheel where the transmission comprises a hydraulic pump and a hydraulic motor each having a pumping mode and motoring mode. The pump and motor each have cylinders of cyclically varying working volume in which hydraulic fluid displacement through each cylinder is regulated and in phased relationship to cycles of cylinder working volume with reference to a phase signal. The transmission has a first mode in which the pump and motor are fluidly connected to each other, a second mode in which energy from hydraulic fluid pressurised by the motor in the pumping mode is transferred to an energy store, and a third mode in which energy from the energy store drives the motor, and wherein the motor comprises a valve assembly disposed between a high pressure line and a working chamber of the motor.

A series hydrostatic transmission for a vehicle having a wheel where the transmission comprises a hydraulic pump and a hydraulic motor each having a pumping mode and motoring mode. The pump and motor each have cylinders of cyclically varying working volume in which hydraulic fluid displacement through each cylinder is regulated and in phased relationship to cycles of cylinder working volume with reference to a phase signal. The transmission has a first mode in which the pump and motor are fluidly connected to each other, a second mode in which energy from hydraulic fluid pressurised by the motor in the pumping mode is transferred to an energy store, and a third mode in which energy from the energy store drives the motor, and wherein the motor comprises a valve assembly disposed between a high pressure line and a working chamber of the motor.