Abstract: Disclosed are a crane and a control method therefor. The crane comprises a body, a boom, a luffing mechanism, a tension sensor, and a controller. One end of the boom is rotatably connected with the body. The luffing mechanism is respectively connected to the body and the boom. The tension sensor is disposed on the luffing mechanism, and the tension sensor is used for detecting a tension value of the luffing mechanism to the boom. The controller is electrically connected to the tension sensor and the luffing mechanism, and the controller is configured to determine that the arm length of the boom exceeds an arm length threshold if the tension value is greater than a tension threshold.

Abstract: A buffer unit for the slewing platform of the tamping machine, comprising a slewing plafform, a slewing bearing and a chassis, the upper end of the said slewing bearing connects to the slewing plafform and the lower end of said slewing bearing connects to the chassis, the slewing platform can revolve around the chassis 360 degrees, further comprising a annular supporting slab, a hydraulic cylinder and a connecting rod, the annular supporting slab is fixed on the chassis by bolt. The hydraulic cylinder is fitted on the rear end of the central plane of the slewing platform, the piston rod head of the hydraulic cylinder connects to said connecting rod. The connecting rod can touch and support the annular base slab at any point of the direction of 360 degrees rotation when the hydraulic cylinder extends.

Abstract: A buffer unit for the slewing platform of the tamping machine, comprising a slewing plafform, a slewing bearing and a chassis, the upper end of the said slewing bearing connects to the slewing plafform and the lower end of said slewing bearing connects to the chassis, the slewing platform can revolve around the chassis 360 degrees, further comprising a annular supporting slab, a hydraulic cylinder and a connecting rod, the annular supporting slab is fixed on the chassis by bolt. The hydraulic cylinder is fitted on the rear end of the central plane of the slewing platform, the piston rod head of the hydraulic cylinder connects to said connecting rod. The connecting rod can touch and support the annular base slab at any point of the direction of 360 degrees rotation when the hydraulic cylinder extends.