Abstract: This invention relates to an improved shearing device to be mounted on a tree harvesting vehicle having a pair of blade edges which move through inward downward directed arcs in shearing the tree. This movement provides the advantage of reducing cracking or splitting of the butt end of the cut log and additionally shatters the stump below the cut which exposes more of it to more rapid breakdown by the elements following cutting. In one embodiment, the frame of the tree shearing device mounted on the end of a boom mechanism on the vehicle has a U-shaped horizontal portion with spaced apart arms which define a front opening to receive the tree trunk therethrough. A pair of blade members, one of each of which is pivotally mounted on each of the arms, are pivoted inwardly and downwardly from the open to the closed position by a hydraulic cylinder connected to them adjacent their rear ends. A pin and slot connection between the two blade members ensure that they rotate concurrently.

Abstract: This invention relates to a photoelastic load measurement device which measures the load on the cable of the crane by measuring the strain in a particular structural member of the crane and is calibrated to operate an alarm, indicator and/or recorder. A source of polarized light directs a beam of light through a photoelastic plate to an analyzer plate and a photocell. The photoelastic plate is subjected to stress from the structural member which varies with the load on the cable of the crane. The stress in the photoelastic plate subjects the beam of polarized light to temporary double refraction (birefringence), and the intensity of the light received by the photocell through the analyzer plate is dependent upon the degree of retardation of the light in the photoelastic plate. The output signal from the photocell is amplified to operate the alarm, indicator and/or recorder. The device includes apparatus which automatically compensates for changes in ambient temperature and variations in boom angle.