Abstract: An improved track tensioning and recoil arrangement for crawler track drive systems is disclosed which uniquely functions to tension the crawler tracks responsively to the load thereon. The arrangement includes a pair of hydraulic drive motors respectively associated with each of the crawler tracks for independent operation thereof. Tensioning of the tracks is provided by a hydraulic tensioning cylinder assembly. In order to tension the tracks responsively to the torque applied thereto by the drive motors, branch hydraulic fluid lines are provided from the fluid supply lines for each hydraulic motor to the tensioning cylinder assembly of the respective track. By this arrangement, tension in the track is increased as torque applied to the track by its drive motor is increased. In the preferred form, pressure relief valve means are provided in communication with each tensioning cylinder assembly in order to relieve pressure within the tensioning cylinders if it exceeds a predetermined value.

Abstract: A boom and dipper stick construction for mobile excavators and an improved method of manufacturing the same. The boom and dipper stick are fabricated from side plates that are butt welded together with respect to various hinge point locations to eliminate the necessity of doubler plates on the sides of the structures. The butt welds are located at non-critical areas to provide for even stress flow and ease of manufacture.A method of welding together the side plates of the boom and dipper stick construction in an end to end abutting relationship in a manner which attains a complete weld penetration over the entire length of the joint.