Abstract: This disclosure relates to a novel tracer head comprising a stylus, stylus support and housing, and two perpendicular differential transformers. The stylus has a unique configuration enabling more precise memory of its null position when the stylus is not deflected. Further, the stylus has a rotating top pin for contacting the pattern or template that assures a condition assumed in tracer control systems but not achieved under all conditions, i.e., the stylus will deflect away from the template normal to the template edge.

Abstract: An elongated shuttle car is provided having a set of undriven rail wheels and a set of driven road wheels. The rail wheels are movable between a lowered position wherein they support the shuttle car and a raised position wherein the shuttle car is supported from the road drive wheels. The road drive wheels are independently driven by fluid drive motors, one of which is associated with each road wheel. The road wheels are disposed so as to permit movement of the shuttle car generally perpendicular to its longitudinal axis which is aligned with the rail bed. Hydraulic cylinders or jacks are utilized for raising and lowering the undriven rail wheels which are normally formed of steel. The rail wheels are supported in movable truck assemblies. The movable truck assemblies have an axle permanently attached thereto and a pair of rail wheels are attached to the ends of the fixed axle.

Abstract: A two-stroke engine having an improved piston construction which reduces friction and wear between the piston and the cylinder wall, thereby providing cooler operation at any selected speed. The decreased wear increases piston life. The piston skirt, which is substantially parallel to the cylinder wall during normal operation, has a plurality of circumferentially spaced openings formed therethrough. These circumferentially spaced apart openings or holes, which are of a relatively small cross-sectional area compared with the area of the ports, are aligned with vertical continuous portions of the cylinder wall. The openings of the inlet, outlet, and transfer ports are located between the vertical continuous portions or ribs of the cylinder. The piston is disposed within the hollow inner portion of the cylinder for relative reciprocating motion. The openings in the cylinder skirt are aligned to move along the vertical ribs.

Abstract: A self-propelled vehicle having independently steerable and suspended wheel assemblies for use in underground excavations. The vehicle includes means for temporarily supporting the roof of an excavation, drilling holes in the roof, and inserting bolts therein. The vehicle also includes scoops mounted at each end with a conveyor joining the scoops, thus giving the machine a self-loading capacity. The application also discloses a method for systematically installing roof bolts.