Power take-off is an important part of a small crane, which is mainly used to draw power from the chassis transmission to drive the hydraulic pump, that is, after the power of the vehicle internal combustion engine is transmitted to the transmission, the power take-off obtains power from the intermediate shaft of the transmission, and drives the hydraulic pump to supply pressure oil to the executive parts of the crane through a special transmission shaft to complete various actions of lifting operation. Hydraulic pumps are generally gear pumps or piston pumps. Gear pumps include single pump, double gear pump and triple gear pump. Domestic wheeled cranes use piston pumps, while Japanese imported cranes use double gear pumps and triple gear pumps. When the crane is running, the hydraulic pump must be disconnected from the engine. Power take-off combination control, some members operate in the cab, that is, manual gear shifting and gear selection; Most of them use electromagnetic control power take-off to shift gears and pick gears. First, the power take-off control device runs at a low speed for a period of time after the internal combustion engine is started. After the internal combustion engine temperature and lubricating oil pressure are normal, the power take-off can be combined with operation. When the hydraulic pump needs to be driven, turn on the power switch of the power take-off and press the clutch pedal at the same time, and the indicator light 12 of the power take-off lights up, indicating that the hydraulic pump has started to work. At this time, the speed of the hydraulic pump can only be controlled by the boarding cab, and the accelerator pedal of getting off the bus does not work. When it is necessary to stop the hydraulic pump, step on the clutch pedal in the cab, turn the switch of the variable speed power take-off to the off position, the indicator light of the power take-off goes out, and the accelerator pedal resumes the function of controlling the engine speed, so that the crane can move. Generally, a tire crane has only one cab, and the engagement and disengagement of the hydraulic pump is controlled by the engagement (disengagement) joystick or switch of the hydraulic pump in the cab. Second, the manual power take-off Some wheeled cranes use a manual power take-off and install it on the power take-off window of the crane transmission with bolts. It is a three-shaft gearbox, and the big gear on the transmission tower gear often meshes with the power output gear of the auxiliary shaft of the transmission. The power of the engine is input by the driving tower gear, transmitted by the gears on the intermediate shaft and the main shaft, and finally output by the connecting flange on the main shaft. The hydraulic pump is driven by the universal transmission shaft. Use the shift lever to shift the fork shaft, move the sliding tower gear, and complete the shift (on) and shift (off).