Abstract: For a device having first and second, centrally-bored conduits in substantially collinear alignment along a longitudinal axis, the method checks collinearity of the conduits. Each conduit has a discrete inside diameter, and the method comprises directing light through the conduit which has the greatest inside diameter and displaying the light on a planar surface, downstream thereof, as a circular image. Then, light is directed through a second of said conduit create an emerging beam, and displaying the beam on the planar surface to ascertain its central, or offset, impingement relative to the circular image.

Abstract: In the embodiment disclosed, the invention comprises a single, dual-piston cylinder, operable by hydraulic fluid, interpositioned between a pair of pivotably coupled, vehicular units. The cylinder is pivotably secured to pivot coupling elements which join the units, and each piston has its translating rod pivotably coupled to one of the units. Ports opening into the cylinder admit and discharge operating, pressured, hydraulic fluid (a) to displace the pistons apart, whereby a first crab steering is effected, (b) to move the pistons into mutual proximity, whereby a second, alternate crab steering is affected, (c) to displace the pistons in unison, in a first direction, whereby a left-hand or right-hand steering is effected, or (d) to displace the pistons in unison, in an opposite direction, whereby the opposite-handed steering is effected.

Abstract: A master link assembly in a continuous flexible track assembly for a crawler tractor comprises two laterally spaced apart (left and right) parallel master links and each master link comprises two overlapping half-links held in alignment and mechanically secured together in fixed relationship by track shoe capscrews which extend through holes in a master link track shoe which overlies both half-links and screw into tapped capscrew holes in the half-links.

Abstract: A fiber optic system for permitting viewing of any of a plurality of selectable remote scenes in hostile environments by direct image transmission to the observer outside of the environment of the scenes. An optical image of each scene is transmitted by separate fiber optic bundles to an optical selector system which redirects the transmitted image through a single bundle where the image is presented in a form for viewing by the observer. The system is particularly useful in troublesome environments such as are encountered in the high pressures outside vessels or noise radiation sources where conventional television viewing systems can be used only with special insulation or containment.