Rear axle problems

Details

Tramping in Abingdon

In 1996 Paul Batho had the chance to speak to Peter Tothill, who worked at Cowley for 32 years from 1950, first in the experimental department and later in production engineering.
 He was told a fascinating tale:
 In the autumn of 1953 the ZA Magnette was about to be launched and Peter Tothill and a colleague were carrying out a road test on one of the three prototypes. This was a high speed run, and the practice was to use the Witney Road which, as it heads west from Oxford runs flat and pretty straight, parallel with the river. Discs on poles werde unofficially stuck into grass verge as distance markers, and timing was by stopwatch held by the passenger. Being part of the A40, this was, and remains, a major road and in those days was a three lane highway, with a central 'suicide' lane for overtaking in either direction. Traffic was a lot lighter than now, and the testers simply used to wait for a reasonable gap in the traffic before flooring it and getting a run on a clear road. Those were the days! On this occasion they allowed what they thought was a sufficient gap, but, on coming overm the bridge which spans the canal and railway, a slower car was unexpectedly met. The overtaking lane occupied with oncoming traffic and so it was hard on the anchors and hope for the best. "lt was terrifying" Peter told me " The car developed violent axle tramp which built up and up. lt became quite uncontrollable and we were all over the road." Amazingly, the car eventually slued to a halt without hitting anything but it was driven straight back to Cowley to try to sort out the problem. These prototype cars were fitted with the torque arm arrangement that is described above. Peter told me that this was principally because the Magnette was considerably lower slung than the Wolseley 4/44 with which it shared the majority of its body shell, and it had been feared that this would cause the prop shaft to strike the tunnel when the rear springs were fully depressed. The torque arm was designed to twist the nose of the axle down in these conditions, thus lowering the shaft. A further benefit was thought to be more positive location, but Peter's near accident had shown that the opposite was the case- heavy braking caused the axle to wind up on its forward mounting shackle and then release, with disastrous results. BMC had two concerns: time and money. The car was about to be launched, and production had begun. And as well as the delay, there was a marked reluctance to spend much more an development. So rather than doing anything fancy, out came the old fashioned U-bolts and the axle was strapped conventionally to the springs. The 50 or so cars that had already been built were modified and full production commenced, albeit rather delayed. But what about the tunnel problem? Easy, just lie under your car and compare the bump-stop arrangements with those in the diagram. The rubber cone is now mounted on the axle while to the chassis member above has been welded (if it hasn' t rusted away) a steel bump stop that stops the axle having that extra inch or so of travel. No doubt the bean counters at Cowley and Abingdon were delighted at the cost savings, though if you' ve ever thought that the ride in the rear of your car was a little stiff and joggly - well, now you know why! One other odd thing about this story - the designer of the Magnette, Gerald Palmer, also designed the Riley Pathfinder at about the same time. Or Ditchfinder, as it came to be known, due to problems with the location of the rear axle. Well, nobody's perfect. ..