1. It converts the Rotary movement of the steering wheel in to the angular turning of the front wheels.
2. It also multiplies drivers efforts and give MECHANICAL ADVANTAGE.
Types of Steering Gear Boxes:
1.Worm and Wheel Type
2. Re-circulating Ball Type
3. Rack and Pinion Type
4. Cam and Lever Type
5. Worm and Sector Type
1.Worm and Wheel Type: This type of steering gear has a square cut screw threads at the end of the steering column; which forms a worm, at the end of it a worm wheel is fitted and works rigidly with it. Generally covered shaft is used for the worm wheel. The worm wheel can be turned to a new position the drop arm can be readjusted to the correct working position.
2. Re-circulating Ball Type: In this type of gear box the endless chain of balls are provided between the worm and nut members. The nut form a ring of rack having an axial movement. So that the sector on the rocker shaft racks, the balls roll continuously between the worm and nut. Being provided with return chambers at the ends of the worm. This method reduces friction between worm and nut members. This type of steering gear is used for heavy vehicles.
3. Rack and Pinion Type: This is common manual type of steering gear box is used in most of the vehicles. In this type of steering a pinion is provided the bottom end of the steering column. The teeth of the pinion wheel in mesh with corresponding teeth provided on the rack, the end of which are connected to the stub axle through the rod. The rotating motion of the pinion operates the rack in FORE and AFT direction which in turn operates the stub axle.
4. Cam and Lever Type: The cam and lever steering uses one or two lever studs fitted in taper roller bearing. When the worm in the form of helical groove rotates the stub axle and it also rotates along with it. This imports a turning motion to the drop arm shaft.
5. Worm and Sector Type: In this type the worm on the end of the steering shaft meshes with a sector mounted on a sector shaft. When the worm is rotated by rotation of the steering wheel, the sector also turn rotating the sector shaft. Its motion is transmitted to the wheel through the linkage. The sector shaft is attached to the drop arm or pitmen arm.
Power Steering:
Power steering reduces much strain on the part of the driver while negotiating sharp curves. It makes easy to turn sharp corners. It is usually arranged to be operative when the effort of steering wheel exceeds a predetermined value. It is fitted on heavy commercial vehicles and medium cars.
