<P> The rack carries the full load of the actuator directly and so the driving pinion is usually small, so that the gear ratio reduces the torque required . This force, thus torque, may still be substantial and so it is common for there to be a reduction gear immediately before this by either a gear or worm gear reduction . Rack gears have a higher ratio, thus require a greater driving torque, than screw actuators . </P> <P> Most stairlifts today operate using the rack and pinion system . </P> <P> A rack and pinion is commonly found in the steering mechanism of cars or other wheeled, steered vehicles . Rack and pinion provides a less efficient mechanical advantage than other mechanisms such as recirculating ball, but less backlash and greater feedback, or steering "feel". The mechanism may be power - assisted, usually by hydraulic or electrical means . </P> <P> The use of a variable rack (still using a normal pinion) was invented by Arthur Ernest Bishop in the 1970s, so as to improve vehicle response and steering "feel," especially at high speeds . He also created a low cost press forging process to manufacture the racks, eliminating the need to machine the gear teeth . </P>

Advantages and disadvantages of rack and pinion pdf