4.1.24 Rack-And-Pinion Drive Machine
(a) consist of one or more power-driven rotating pinions arranged to travel on a stationary rack mounted on the supporting structure.
(b) have at least one pinion, one rack, and two backup rollers, where at least one pinion, one rack, and one backup roller shall act on the same section of rack as the drive pinion. Driving machines using a two-sided rack, where two drive pinions are located so that they are opposite each other and act as backup rollers, shall be deemed to have met this requirement.
(d) have the rack and pinion designed to limit the separation of the pinion from the rack in all directions to 25% of the tooth depth or 6 mm (0.25 in.), whichever is greater.
(e) have the pinion guarded to prevent foreign material from falling onto and lodging between the teeth of the pinion and rack. The clearance between the moving parts and the guard shall not exceed 5 mm (0.1875 in.).
(f) be provided with a sign that shall
(1) include information on checking tooth wear of the pinion and rack
(2) show the maximum allowable wear limits for the rack and the pinion
(3) be metal securely fastened and conspicuously displayed on top of the car with permanent lettering not less than 3 mm (0.125 in.) high
(a) Pinions and racks shall be steel or material having mechanical properties equivalent to or better than those of steel, with a minimum factor of safety of 8 based on ultimate stress for the pinion and the rack. They shall be designed to conform to AGMA 218.01, including surface hardening and an assumption of a minimum of 200000 life cycles.
(b) Rack sections shall be fastened to the supporting structure with a factor of safety of 5 based on ultimate stress and with dowels at each joint.