How are rack and pinion and Recirculating-ball used in car steering?

●Rack and Pinion Steering

Rack and pinion steering is quickly becoming the most common type of steering on cars,small trucks and SUVs.It is a very simple mechanism.The rack and pinion set is enclosed in a metal tube,with each end of the rack protruding from the tube.A rod called a tie rod is attached to each end of the rack.A pinion gear is attached to the steering shaft.As you turn the steering wheel,the gears rotate,moving the rack.The tie rods at each end of the rack connect to the steering arms on the spindle. As shown in the picture below.

Car steering working principle

The rack-and-pinion gearset does two things:①It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.②It provides a gear reduction,making it easier to turn the wheels.

When the rack is located in the power steering system,the rack has a slightly different design.Part of the rack contains a cylinder with a piston in the middle.The piston is connected to the rack.There are two fluid ports,one on either side of the piston.A high pressure fluid supply to one side of the piston forces the piston to move,which in turn moves the rack,providing power assist.

Rack-and-pinion for power steering system

●Recirculating-ball Steering

Recirculating ball steering systems have been used in many trucks and SUVs.The linkage that turns the wheels is slightly different than a rack and pinion system.Recirculating ball steering contains a worm gear.You can image the gear in two parts.The first part is a piece of metal with a threaded hole in it.The outside of the block has gear teeth cut into it,which engage a gear that moves the pitman arm.

The steering wheel is attached to a threaded rod similar to a bolt that is inserted into a hole in the block.When the steering wheel is turned,it turns the bolt.The bolt is not twisted further into the block as a normal bolt would be,but is fixed and secured so as to move the block as it rotates,thus moving the gears that turn the wheel.

Recirculating-ball for car Steering

Rather than the bolts directly engaging the threads in the block,all the threads are filled with ball bearings that recirculate through the gears as they turn.The balls actually serve two purposes:first,they reduce friction and wear in the gears;second, they reduce slop in the gears.When you change the direction of the steering wheel,the slop is felt - without the balls in the steering,the teeth temporarily touch each other,making the steering wheel feel loose.Power steering in a recirculating ball system is similar to a rack and pinion system.It is aided by supplying high pressure fluid to one side of the block.

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