Steering Column: Description and Operation

The energy absorbing function of the steering column allows the column to collapse at a controlled rate during a severe collision. The collapsing action reduces the possibility of the steering wheel being driven rearward towards the driver. If the driver is thrown forward into the steering wheel, the column can collapse even further at the same controlled rate, thereby reducing the force of impact.

Several designs of steering column jackets are used. There is the slip tube design which is held together with plastic inserts or rivets that shear upon impact and allow the column to collapse. And there is the slotted or corrugated mesh design and bellows type design which shorten in length during impact.

The shift tube is a two piece design which is held together by injections of plastic that form the interconnecting inserts and shear pins. Under impact, there is a gradual paring away of the inserts by the knife-like edge in the adjoining tube section.

The steering shaft is a two piece assembly. The upper piece is solid and has a double flattened lower end. The lower piece is hollow and formed to fit over the double flattened section of the upper piece. The purpose of the double flattened section is to provide continued steering action even though the shaft is completely collapsed. Upon impact, the shear pins break off and the shaft gradually telescopes against resistance provided by the plastic injections.

The steering column mounting bracket prevents the column from being shifted towards the driver during impact. It uses two breakaway capsules that allow the mounting bracket to slip off its attaching points, allowing the steering column to compress or yield in a forward direction under a severe impact from the driver's end.