I worked for British Leyland after joining as an Austin Apprentice, and specialising on suspension systems. Along the way, I have been involved in some interesting projects. I helped build the Morris Marina simulators, which were constructed by welding an elongated Morris Minor floorpan onto the underside of a Vauxhall Viva HB bodyshell, and installing an A-Series engine and gearbox from a Spridget.
But a fascinating story for me was how the rear suspension system of the Rover 200 (R3) came about, and how important the Austin Maestro was in its development.
The story goes back a long way. The philosophy of suspensions in general, when narrow wheels and tyres were universally employed on normal saloon cars, was one of great attention to vertical dynamics to achieve a nicely comfortable ride, with very little attention paid to the kinematics and elasto-kinematics, which govern the handling performance of the car.
One of the results of this had been the ever spiralling costs, complexity and reliability of systems, notably at the rear, where such systems of interconnected Hydragas had become commonplace at Longbridge. It was for this reason, I would suggest, that the Minor was re-introduced under the banner of the Morris Marina, but with the cheaper Standard-Triumph rear axle.
However, this was seen as rather retrograde, so work was commenced on Maestro, which rather resembled the Volkswagen Golf in many respects including the inexpensive rear axle. There were many difficulties encountered in the ‘H’ frame design, which looked rather vulnerable, and exhausted many hours of development time in their resolution, perhaps leaving too little time for ride and handling development.
The resulting car worked tolerably well on its fairly unresponsive 145 R13 tyres. However, later developments like the MG, and the heavier Austin Montego with wider, lower profile, more responsive tyres, showed up a weakness in its sideforce steer characteristics, which began to concern us, exacerbated by Volkswagen’s modifications to its ‘H’ frame bushing utilising a wedged bush, in order to improve this aspect of performance.
At about this time we got involved with hydraulically modified bushes (hydrabushes) principally on Rover 800 front suspension, and which excited my mind to the possibilities of using similar technology in other applications such as Maestro ‘H’ frame. I therefore initiated some work on Maestro to divorce axial from radial compliance using solid sliding bushes and soft end snubbing in the one case, and soft bushes with tight clearance solid snubbing in the other.
The result was interesting in that the vehicle handling was far more tolerant of an arrangement allowing significant lateral movement to the frame, than that allowing more longitudinal (and hence steer) movement. Therefore, I started thinking of ‘H’ frame bushes which would contain an oil-filled void in the side snubbers (ears), interconnected to a void in the radial direction at the back of the bush, which would impart a corrective steer movement at the expense of some side travel.
So, we started doing some ‘pull’ tests to establish the magnitude of the undesirable sideforce steer angles, and correlated with the specially adapted bushes as assessed on the road. It was from this work that we estimated the ideal magnitude of required ‘good’ sideforce steer, being about as much as measured ‘bad’, but in the opposite direction.
It was then that I communicated the findings to Spike Hawthorn to see what he thought of the proposal. We worked with Avon Rubber Company, during which it was decided that, whilst a hydramount type bush could work, a conventional bush angled in plan view to the vehicle centreline would be a more cost effective feasible solution.
So, Spike set to designing a suitable bush and angle, to achieve the desired characteristics, whilst experimentation continued on Maestro and Volkswagen Golf with its wedged bush to refine the requirements.
A Rover 200 (R8) car was modified to accept a suitably modified Maestro frame to Spike’s recommendations (5:1 stiffness ratio at 25 deg), and was evaluated on the road and test rig. The graph (below), found by Spike (lining a drawer!), illustrates the kind of results, plotting side load on the horizontal axis, and steer angles on the vertical axis. The lower pair of curves depict typical behaviour of the angled bush – presumably both rear wheels, while the upper is thought to represent the Volkswagen performance.
The points of flexure on the lower curves represent the point of contact of the end snubbing of the bushes. It was established with Thyssen that there were no serious frame manufacturing problems posed by this angling, and various ancillary work like tyre clearances proved acceptable, so there was sufficient confidence to restart the R3 project, with the considerable cost savings identified by Dave Beadle.
At this point Jonathan Cox (Design) and Derek Irving (Development) did some considerable work to take the project to its final design during which a crosswind stability problem was identified on road tests, which related to this point of flexure, and identified and implemented means of its amelioration. The overall steer performance of the car was seen to represent a big improvement over Maestro, and suitable for R3.
If you were at the coalface and have a tale to share, please do get in touch!