JUDGMENT
1 HIS HONOUR: On 21 November 2002 the plaintiff was severely injured driving to work when an International Transtar F4670 prime mover and semi-trailer ("the truck") driven by the first defendant collided with his car on the Bogan Road near Parkes. The truck was travelling in the opposite direction and crossed onto the incorrect side of the road. The accident was caused by a failure of the steering mechanism in the truck, which was manufactured by the second defendant. Damages were agreed on the first day of the hearing. The issues remaining for determination are therefore now limited to the question of the defendants' liability (if any) to the plaintiff and to resolution of cross claims filed by each of the defendants against the other.
2 The plaintiff alleges that the first defendant failed properly to service or maintain the truck. In particular, the plaintiff alleges that the first defendant failed to maintain the steering mechanism and other associated mechanical parts or to inspect them in a way that would and should have revealed whether or not a clamping bolt in a universal joint had been adjusted to a torque setting that would have prevented an intermediate shaft from becoming detached from the joint leading to a loss of control. This is necessarily explained and considered in more detail later in these reasons. Although the claim against the first defendant as originally pleaded included allegations relating to the way in which he drove, managed and controlled his truck, these were abandoned at the trial (if not well before) in deference to an uncontroversial recognition that the collision was caused by mechanical failure unrelated to any aspect of his driving.
3 The plaintiff alleges that the second defendant manufactured the truck with design defects in the steering mechanism that rendered it liable to become disengaged either as the result of a loose universal joint clamping bolt or loose bearing grub screws or both. There was no claim that it was constructed or assembled poorly, as opposed to complaints about its design. This is also necessarily explained and considered in more detail later in these reasons. The plaintiff alleges in addition that the second defendant failed to produce and supply an owner's or operator's manual or handbook for the truck that specified that regular inspection and/or maintenance of the steering mechanism and/or all steering linkages was required. A claim relying upon s 75AD of the Trade Practices Act 1974 was abandoned.
4 By his amended first cross claim the first defendant claims contribution from the second defendant alleging that it was negligent in the same respects pleaded by the plaintiff against him. The first defendant also relies upon s 74AD and s 74AE of the Trade Practices Act 1974. There is in effect a corresponding claim by the second defendant against the first defendant in the third cross claim with the exception of the statutory counts. These cross claims are referred to below.
The steering system and the mechanism of its failure
5 It is essential at an early stage to understand the steering mechanism of the first defendant's truck and the particular parts of it that are said to be inculpated in the ultimate failure that resulted in the complete loss of control that he experienced immediately before the collision. Potentially two portions of the truck's steering system are involved. The first is a universal joint connecting the intermediate shaft to the upper steering column. The second is a seized bearing in a flangette housed on the engine side of the firewall, in conjunction with the absence or inappropriate adjustment of grub screws intended to attach the intermediate shaft to the inner surface of the bearing. These are described in turn.
6 First, there was agreement among the experts that the likely sequence of events that led to the loss of steering included the disengagement of a clamped connection between the universal joint connecting what is known as the intermediate shaft and the upper shaft of the steering system. This universal joint was located within the cabin of the truck encased in a removable housing attached by six screws. It was situated immediately below the steering wheel in a position between the driver's legs.
7 The universal joint comprised two yokes connected by a central spider. The end of each yoke consisted of a split, splined housing designed to accommodate a splined shaft. This was, in lay terms, a circular opening into which the splined end of the intermediate shaft was inserted. The splines on the shaft mated with the splines in the opening. The shaft was fixed into the universal joint by inserting the matching splined splint housing of the yoke and placing a pinch bolt (sometimes called a clamp bolt or clamping bolt) into a clearance hole in the joint so that the bolt intruded into the groove of the splined shaft. The bolt was secured in place by means of a nut. The bolt passing through the hole to a corresponding hole on the opposite side was to be tightened to a specified torque of between 45Nm to 50Nm. In that configuration the shaft was secured in its position within the universal joint by mechanical force exerted upon the joint by the tightened bolt and the marrying of splines on the end of the intermediate shaft with corresponding grooves upon the inner surface of the opening in the universal joint.
8 Prior to the collision the locking of the splined shaft into the universal joint had been compromised by progressive loss of the bolt volume due to wear of that part of the bolt within the groove. Some localised wear of the splined shaft was also evident, particularly in the section of the groove and the adjacent splines closer to the end of the shaft. The wear would appear to have occurred concurrently on both the bolt and the shaft and the wear was predominantly asymmetrical. The worn section of the bolt used to secure the spline of the steering shaft to the lower yoke of the universal joint was grooved in a pattern consistent with the contours of the splined shaft. Eventually the bolt became ineffective in locking the shaft and the assembly, consisting of the universal joint, the steering column and the steering wheel separated from the splined shaft.
9 The attachment of the upper yoke of the universal joint to the steering column was achieved in the same way. A short splined section 20mm long of a 25mm diameter shaft at the base of the steering column allowed connection to the universal joint. This shaft was also grooved circumferentially to allow a pinch bolt connection to the joint. Although on examination this joint was still intact, axial sliding could be effected over a distance of about 2mm, indicating that the securing bolt was not producing a snug fit in the groove of the splined shaft. Inspection of this bolt showed that wear had commenced in the region contacting the surface of the groove in the splined shaft and that it also contained wear grooves parallel to the splines that had been produced by relative motion between the bolt and the shaft. Some wear of the splined shaft was also evident. One of the experts described the condition of this bolt as in effect a "snapshot" of the condition of the failed bolt from the joint of the lower yoke at an earlier state of wear.
10 In the present case the vibration or slip was axially directed because the mating of the splines in the universal joint with the splines in the shaft prevented relative rotation. That is confirmed by the axial wear pattern on the bolts that corresponded to the shape of the contours of the upper and lower splined shafts.
11 Fretting wear was the main mechanism of failure. The essential feature of fretting is the presence of small amplitude vibrations in a nominally stationary joint. The upper and lower universal joints that respectively connected the steering column assembly and the splined steering shaft to the yokes of the universal joint were subject to vibratory forces during normal use of the truck by transmission from the engine and the wheels. Slip or relative motion between the mating surfaces resulted in adhesive wear due to micro welding and fractures of asperities on the surfaces of the mating steel components. As wear progressed, the amplitude of the movement also increased, producing significant slackness in the joint. In addition to increased sliding contact, impact loading of the joint components is also likely to have occurred. This would have increased the rates of wear caused by both adhesion and abrasion. The key cause of the failure in the present case was the relative motion between the bolt and the splined shaft. Professor Dunne originally opined that the possible reasons for this included poor fit of the mating components and insufficient tightening ("torquing") of the locking or pinch bolt. He appears to have resiled from the former contention during cross-examination. The second contention was accepted by all of the experts.
12 Secondly, the intermediate shaft of the steering mechanism passes through the firewall of the cabin of the truck and into the engine bay via a housing for a flangette and its fitted bearing. The shaft is secured or located axially to the bearing by two grub screws, so that they rotate together when turned. When examined following the collision at least one of the grub screws was found to be missing and the other was partially unscrewed and, according to one expert account, buried in a hard mixture of grease and dirt. The bearing itself was found to have seized. There were witness marks scored into the intermediate shaft at this location suggesting or demonstrating that the shaft had rotated within the bearing, instead of with it, and that this had been caused by the missing or ill-adjusted grub screws, which were not operating to locate it to the shaft. Rotation of the shaft in this way, unlocated to the bearing, therefore continued to occur notwithstanding that the bearing had seized. But for this behaviour, steering of the truck in any way at all would have been wholly prevented or at least significantly inhibited.
13 A conclave of experts on 29 January 2009 produced answers to a series of questions that included the question, "What [was] the likely cause as to the collapse of the steering column?" The answer given by the experts was in the following terms:
"1. The disengagement of the universal joint from the intermediate shaft was caused by gross fretting under the effects of normal operational vibration over a long period.