Steering (Description): Description and operation (page 2 of 4)

1 Locknut 2 Steering wheel 3 Upper shaft 4 'U' Clip (2 off) 5 'Curling' plate (2 off) 6 Shear bolt (2 off) 7 Clamp plate 8 Lower mounting 9 Upper column tube 10 Lower column tube 11 Universal joint 12 Intermediate shaft 13 Universal joint 14 Adaptor 15 Clamp bolt 16 Locknut – mounting (2 off) 17 Upper mounting 18 Column adjuster 19 Light ring – ignition switch 20 Transponder coil 21 Steering column lock assembly 22 Lock bolt 23 Ignition switch 24 Lower shaft 25 Injection moulded shear pins 26 Lock collar 27 Wave form interference ring

The steering column design incorporates an energy absorbing mechanism to reduce driver impact loads in the event of a collision. The column is mounted on four captive studs which are located in an extension to the bulkhead. The two lower mountings are fixed and cannot move when loads are applied to them. The upper mounting is designed to disengage or deform when a load is applied, allowing the column to collapse in the event of an accident. The steering column is adjustable to allow the steering wheel to be moved vertically up or down to the desired position. The steering column is not serviceable and must be replaced as a complete assembly if necessary.

The upper column tube is telescopic and can slide over the lower column tube. The upper column tube provides for the location of the steering lock and ignition switch and also the steering switch gear and a rotary coupler. The rotary coupler provides the electrical connection for the steering wheel mounted airbag and the switches for the horn and, where fitted, In-Car Entertainment (ICE) and cruise control.

The central shaft comprises of two parts and is located in bearings in the upper and lower column tubes. The upper shaft is located inside the lower shaft. Mating cross holes in each shaft are connected by nylon injection moulded shear pins.

The upper shaft is splined to accept the steering wheel. The lower shaft is connected by a universal joint to the intermediate shaft. A second universal joint on the opposite end of the intermediate shaft is attached to a split adaptor. The adaptor is splined and mates with the splined input shaft from the steering rack.

The upper mounting bracket has two open slots with a PTFE coated, metal 'U' clip over each slot. Two soft metal 'curling' plates are riveted to the mounting bracket and cover the slots.

The mounting studs pass through the 'U' clips and the curling plates. The lock nuts that retain the upper mountings to the bulkhead extension are tightened to between 12 and 15 Nm. This torque figure controls the breakout load required to move the upper mounting brackets from the studs in the bulkhead extension and is critical to the crash performance of the column.