STEERING GEARBOXES

A Presentation byPUSHPAJEET

INTRODUCTION • To make steering of vehicle easy we require a gear reduction

arrangement, for this purpose steering gearbox came in use.

REQUIREMENT

• To change the rotary motion of steering wheel into straight line motion .

• To minimize the effort of vehicle steering .• Variation of gear ratio from 12:1 to 30:1.

TYPES• Worm and worm wheel• Worm and nut• Worm and nut• Recirculating ball type• Rack and pinion

1.WORM AND WORM WHEEL STEERING GEAR

• There are square threads or worms on the steering rod end which engages in a worm wheel .

• Worm wheel is connected to a drop arm .• When driver rotates the steering wheel ,drop

arm moves forward or backward resulting in motion of stub axle.

• The arc movement of the drop arm is usually from 60 to 90 deg.

• This system is commonly used in tractors .

2.WORM AND NUT STEERING GEAR • Steering rod end have

worm.• worm is connected with

a nut arrangement • When worm rotates, the

nut is able to move • Movement is along the

axis of column either up or down .

• This move cross shaft in arc which also move drop arm .

• This is used in steering all wheels

3.WORM AND ROLLER STEERING GEAR • Worm and roller gear have two

teethed roller which are fastened to the cross shaft called roller shaft or sector shaft.

• The threads of the worm gear are meshed with roller shaft at the end of the steering tube.

• Dia of worm is greater at end and reduced at center .

• When the worm shaft is turned by the steering tube, the roller will also be moved in an arc for rotating the roller shaft .

• The bearings are designed to resist both radial and end thrust.

• Used in Leyland and American passenger car

4. RECIRCULATING BALL TYPE STEERING GEAR

• It consists of a worm at the end of steering rod.

• A nut is mounted on the worm with two sets of balls in the groves of the worm , ball reduces the friction between nut and worm .

• The teeth of nut is meshed with teeth of worm wheel sector to which drop arm is mounted .

• By turning steering wheel , the balls in worm roll in the grooves and cause nut to move alone the length of worm, balls recirculates through the guide.

• Movement of nut causes the wheel sector to turn and actuate the link rod through the drop arm resulting in desired steering of wheels .

• Teeth on the nut are tapered to minimize the wear

• Used in TATA standard 20 vehicle

5.RACK AND PINION STEERING GEAR

• A pinion is mounted at the end of steering gear shaft .

• Pinion is engaged with a rack which have ball joints at end for rise and fall of wheels .

• On revolving pinion rack moves to and fro.• Due to this movement tie rod and stub axle

also moves and we get desired steering .• This system is popular in small cars like

Maruti 800. • Its gear ratio is limited by the diameter of

steering wheel and pinion gear hence can’t used in heavy vehicles