quote:
Originally posted by BEX308
... Shelby American came to when they convinced AC to change over to R&P.
With respect, I would be very interested to see any evidence that Shelby American had to persuade AC Cars to fit R&P steering. It is more likely, in my view, that the changes came as a result of professional engineering discussions and an agreed programme of progressive improvement.
Well before the Cobra, AC Cars had significant experience of the use of R&P, even as early as their first 4-wheeled car in 1911! The general motor industry understanding of the workings of independent front suspension and different steering systems had moved on leaps and bounds since the days of the Ace design in the early 1950s, and the evidence points to AC being very well aware of any limitations in the cam and peg steering design and, perhaps more importantly, the transverse leaf suspension design, when work started on the Cobra.
There are a number of factors which lead to this point of view. In the 8-year period between Ace and early Cobra designs, AC had completed at least two new "clean sheet" road car designs. Both designs had R&P steering and much more sophisticated suspension than the Ace/Cobra. The 1959 AC Greyhound was in production well before the start of Cobra production, and the early 1960's MA200 was almost certainly designed and probably built some time before the Cobra R&P update. In the case of MA 200, the steering design was completely different, at that time an innovative solution to the inherent problems of R&P.
The earliest Cobra was of course a rapidly introduced update of the much earlier mid 1950s Ace design, which was quite possibly due to be superceded when Carroll Shelby knocked on Thames Ditton's door. But, Shelby and Ford were in a hurry and changes to the old Ace design was probably the best solution for a number of reasons. For the earliest Cobras, in order to get series production underway quickly it is reasonable to assume that the minimum changes necessary were introduced, and perforce concentrated in areas other than the steering type.
As can be seen from the posts on page 2 of the 'Cobra (Thames Ditton) Forum mk1 cox and cob', the later conversion of the Cobra to R&P required AC Cars to undertake a major re-design of the front suspension, front uprights, steering and brakes, and other changes to the spring tower and main frame. For series production this required modified jigs and tools, possibly including forging tools, and testing. This was a considerable amount of engineering work with significant production lead times. The changes were so extensive they formed the basis for what is euphemistically, but incorrectly, termed the 'MKII Cobra'.
Chronologically, this all followed the AC Greyhound and probably the AC MA 200 design. No doubt, the Cobra re-design benefitted accordingly. Even then, the fundamental change to a more sophisticated suspension design, more akin to the Greyhound and MA 200, was not introduced to the Cobra line until AC's next major design change, the 1964 MKII coil-spring chassis used for the Cobra 427, the AC 289 Sports and, with a 6" longer wheelbase, the AC 428.
One final question. Is R&P so superior? Currently there are plenty of manufacturers out there who choose not to specify that system.
