Types of Steering Gear Boxes: Steering Systems

There are two basic types of steering systems used on automobiles (cars & buses etc.); the mechanical type conventional/integral (rack and pinion, recirculating ball & nut etc.) steering system and the Power steering gear system, which is also known as HPS or EPS system.

Types of steering gear (operating) system:

1) Mechanical Type Conventional / Integral System:

a. Rack and Pinion Steering Gear.

b. Cam and lever Steering Gear.

c. Worm and Sector Steering Gear.

d. Worm and Roller Steering Gear.

e. Worm & Nut Steering Gear.

2) Hydraulic Type Power Steering System:

a. HPS

b. EPS

3) Electro-Mechanical Hybrid System:

Mechanical Type Conventional Steering Gear System:
1. Rack & Pinion:

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 ends of which are connected to the stub axle through the rod. The rotating motion of the pinion operates the rack in linear (forward and reverse) direction which in turn operates the stub axle.

                                Fig 1: Rack and Pinion

2 Cam & Lever:

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.

                                             Fig 2: Cam and Lever

3. Worm & Sector: 

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 turns 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.

                                  Fig 3: Worm and Sector

4. Worm & Roller:

This type of steering box operates essentially in the same way as the worm and sector. The only difference is that the mechanism that moves the cross shaft is a roller and not a sector gear. The roller in turning the worm gear will force the roller to move along the length of the roller shaft in a twisting motion. Because of the unit mechanism, the worm gear has to be engineered in such a way that it follows the shape of an hourglass.

                                   Fig 4: Worm & Roller

5. Worm & Nut: 

                                     Fig 5: Worm & Nut

Also known as the recirculating ball & nut, the worm and nut type of steering box is inarguably the most ubiquitous of all Pitman arm systems design. What differentiates it from the other types of Pitman systems is that the worm drive is designed to contain more turns complete with a much finer pitch. In this type of gear box the endless chain of balls are provided between the worm and nut members. The nut forms 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. A nut is then clamped over this worm drive before filling it up with ball bearings. It is these ball bearings that loop around or cycle around the worm drive, head towards the recirculating channel located with the box or nut, before the ball bearings find their way to the worm drive again. So, it is these ball bearings that actually travel around the system of worm drive and recirculating channels. A return chamber is provided 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.

Power Steering System: