moment might be expected due to the higher load moment which increases proportionally to the rotary speed in other words when the hydraulic motor due to an excessive load does not reach the preset desired rotary speed it reacts with a further turning back leading to the decrease of the rotary moment to prevent this condition there is again provided the so called loss free pressure limitation by means of the pressure limiting valves 67 and 68 which after responding to a preset maximum pressure permit further setting of the hydraulic motor when the latter valves respond to the crossing of the maximum pressure the dynamic pressure in discharge conduits 99 or 103 propagates via the alternating non return valve 98 and the conduit 97 to the left face of the preliminary control valve 96 this pressure which is now higher than that in the conduit 99 displaces the preliminary control valve 96 into its intermediate position in which the setting cylinder 92 moves the adjusting member 91 of the hydraulic motor to a position which matches the maximum pressure when the high pressure is exceeded the preliminary control valve 96 is brought to its i position whereupon the hydraulic motor is fully swung out and.