mk1 cox and cob

[TLegate]

Tell it to the judge....

[rstainer]

'After 126th car the Ace Bishop worm and sector steering box was replaced by a Cam Gears rack and pinion system' [Cobra Register Introduction].
   
   Nick's maths are beyond reproach: 2125 is the 126th car and 2126 the 127th.
   
   Of more interest is the timing: 2126, the first R&P car, left AC on 31 January 1963 but AC made another 46 Worm & Sector cars in February to July 63. Why did Shelby customers keep buying W&S cars when R&P was on the cards? Two reasons:
   
   

First, although the first AC R&P car left Thames Ditton on 31 January for US approval, Shelby and FoMoCo didn't give the go-ahead until later in February and the next two AC R&P cars (2127 & 2128) only left Thames Ditton on 7th March for air-freight to Los Angeles.
   

   

Second, though, and more importantly, Shelby didn't start marketing R&P cars to the general public until  most previous stock had been sold and the demand for R&P race cars and Shelby/FoMoCo demonstrators and PR cars had been met. The first 22 R&P cars (not exhaustively checked) were race cars, demonstrators and PR cars so the lowest-numbered true 'customer' R&P car was 2148,  ex Thames Ditton on 11th July 63 and sold by Shelby American to Julian Harrison Inc on 12th September 63.

   
   In summary, AC shipped their last W&S cars on the 1st and 2nd July 63 and their first R&P customer street cars on 2nd (2150), 10th (2151, 2 & 3) and 11th July (2148 & 9).
   
   And what of the COX/COB cars, the subject of this string? They didn't start till October 63 and are all R&P: AC's W&S production ended three months earlier.

[riverside]

Thankyou Robin.
   Thats more like it.Any idea what brought the change? ie pressure from Shelby or Turner, who had the other cars to compare to, or just the parts bin just drying out?

[rstainer]

'The parts bin' argument is, I believe, wheeled out in order to (a) avoid the messy business of examining evidence and assessing motives and (b) improve the self-image of the arguer by implying that he would have done a better job than the managers, designers and craftsmen who built the cars in 62 and 63:
   

There is no evidence that AC overstocked components and materials; to the contrary, the evidence is that their stores operation was well run

   

There is no evidence that AC management made anything other than proper engineering decisions

   

The Ace Bishop worm and sector steering assemblies would have been racked, not kept in 'the parts bin'.

   
   I don't think we'll ever know what triggered the change; theories are always welcome, but only if preceded by thought and accompanied by evidence!

[TLegate]

Surely r&p was adopted due to feedback from from racing and noteables such as Ken Miles and Phil Remington? (I think) As evidenced by quotes from Peter Brock and Phil Remington: "The worm and sector cars had such bad bump steer that you'd steer left and, as the front wheel went up, the right one would want to turn right and they'd just tear everything apart" .... "When they came out with the rack and pinion car it started to make a little more sense, but the original worm and sector had over five-eighths-inch toe change. It was really bad".
   
    I guess this is why a number of early Cobras that are used in competition have changed to r&p (2051 et al)?

[rstainer]

I tend to be slightly shy of an argument that starts with 'surely' and finishes with 'guess'.
   
   Unfortunately the 2051 point tells us something about modern 'historic' racing but nothing about period competition. All 2051's extensive period competition history was with worm & sector steering and 2051 was one of the best-preserved of all early period race cars for almost forty years, as could be seen at Silverstone in 98 when the car arrived in the UK.
   
   Its new owner, a fully paid up member of the 'if it makes it go faster, why bother with historical accuracy' persuasion, then revised the car's entire suspension and steering geometry, installed rack and pinion and made numerous further modifications that appeared to shed weight, add stiffness and improve handling.
   
   Simple observation shows that those who race historically correct cars are several seconds a lap slower than the 'why bother with historical accuracy' persuasion. I'd like to illustrate my point with a photo of 2532 (see the register) but the Forum technology defeats me; if anyone emails me the procedure (rstainer@radcothouse.co.uk) I'll post the photo and you'll see a steering assembly (and many other components) unlike any product of AC/Cam Gears or any other 60's supplier.

[TLegate]

No argument here, merely an observation, to be considered and discarded as one wishes.
   
   Along with everyone who contributes to this forum, I was not a employee of AC Cars Ltd., nor Shelby American, during the 1960s. Therefore everything one writes needs to be qualified due to the fact I/we were not there and not party to the decisions that were made.

[B.P.Bird]

Well this is a most interesting thread and touches on the origins of the second style of chassis used on the Cobra. First off can we dispense with this 'worm and sector' description: I believe the Ford Model A (and others) used a steering box that could be described as worm and sector. In any event this incorrect description of the Bishop 'box seems to come from over the pond and is, perhaps, just a carry over from common usage there? Bishop used a system which they described as Cam and Peg and whilst I agree that their cam is in the form of a worm there is no sector, only a peg. So it is Cam and Peg to be absolutely correct - worm and peg if you must.
   As Robin says the system at Thames Ditton was pretty well organised and the whole stores empire, run by old hands like Doug Taylor, did not go in for 'parts bin' engineering any more than did the drawing office. You have to remember how unusual A.C. were at that time: They were a big manufacturer grown small - the opposite progress to marques like TVR or Lotus. A.C. still had all the systems you might find at a Ford or a Jaguar works. So when a steering box, or a steering rack, or a door handle was needed a supply would be negotiated from the likes of Bishop, or Cam Gears, or Wilmott Breeden. The designers and engineers, like Alan Turner, did not look around other car makers parts bins for useful bits and pieces which might do. They obtained specified items from the specialist suppliers and designed them in to their cars. Those specified parts might also be sold, by the parts supplier, to another manufacturer, but as many have found to their cost the A.C. specified part might be different, in essential particulars, from batches produced for other customers.
   The whole question of how Alan Turner revised the Ace 2.6 into the Ace 3.6, subsequently named Cobra, is at the heart of this discussion. It seems clear to me that the short timescales which applied put a deal of pressure on the engineering and therefore A.C. did the job in two 'bites.' Broadly speaking the Ace 2.6 got a new back half, pdq, which went straight into production with the briefest of testing (omitting the ill advised and Shelby inspired inboard rear brakes.) It is informative to work on one of these early cars. The contrast between the sturdy simplicity of the rear hub, upright and wishbone and the fussy detail of the fabricated parts making up the front equivalents is a good lesson in engineering. It is blindingly obvious that two designers have been at work - Turner and Tojeiro.  A short time later the front half got replaced in a style matching the earlier back half. Beginning to sound like a Pantomime Horse. Anyway I believe this was as soon as Alan Turner had completed the design. The idea that the rack and pinion is the only change is a bit wide of the mark. The whole suspension upright and wishbone, wishbone mounts, hubs,discs, calipers, steering and steering column is changed. It is a major redesign of the Ace 2.6 front end, not just the modification to incorporate a rack and pinion. Just producing the steel cast front uprights to replace the entirely different fabricated Ace uprights would need some significant lead time. I find it implausible that the front half design resulted from early competition feed back - no doubt that feedback occurred, but surely Alan Turner was already well advanced in working up the completion of the front half design? He had completed the Greyhound project and done some work on LM5000 in 1958 and 1959, both machines having coil springs all round and rack and pinion steering.
   It has always intrigued me exactly how CS2030 fitted in to this sequence. The time scale fits with the need for a test vehicle for the second Cobra chassis configuration. It would be unheard of for Thames Ditton to put such a radical alteration in to production with no testing and such testing would take a little while would it not? Once completed and accepted then the new chassis could be productionised - new jigs produced, pattern work completed and foundry work set in hand. In those days A.C. could work at amazing speed, free from the parasitic drag of modern institutions like our beloved HSE or VOSA, but not so fast that this kind of change to an existing production line could happen without a development period.
   I remember being told by Jock Wright and Fred Larimore, in period, that 2030 was a development car. I suppose that Thames Ditton would hardly be able to justify a 'demonstrator' to Shelby or Ford given that no early Cobras were sold in the home market. So if either of them picked up the bill for 2030 maybe this was the real reason? I have never looked 2030 over and so my post might well be be misleading, but I wonder if in fact 2030 was the 'mule' for the second Cobra chassis design ?

[rstainer]

Barrie makes some very interesting points and the central proposition, a design in two halves, is correct in both senses: two halves (back, then front), and a proper design, test, production set-up etc for each half. Rinsey Mills' 'AC Cobra' gives a useful account of the front-end changes on pages 40 & 41.
   
   The 2030 suggestion is very interesting, but only inspection would answer it definitively; unfortunately the car was last heard of in a dismantled state thirty years ago and I suspect it may have been destroyed. However the historical facts and timing tie in with Barrie's suggestion:
   

The AC Factory Ledger is noted 'Instructions issued 12 Sept 62', the car was finished towards the end of October and registered in Nov 62. I wonder what the instructions were?

   

The Shelby American ledger lists it as 'AC Test Car'

   

Per my records the car was paid for by Shelby but remained in AC's hands for a year until sold to a Mr Dent on 18 Nov 63.

   
   As Barrie writes, although listed in the Factory Ledger as a 'Demonstration Car', AC had no reason to demonstrate anything. Finally, worm and peg it is: Register Introduction amended.

[riverside]

As per my original question I had visualized that some of the early mk1`s ie cox 6001 to 6062 possibly had started life as cam & peg AND the developement to R&P done on them. Ie This way it did`nt involve Shelby`s orders at all but might well have been requested by Miles, Remington because of the racing experience. As I don`t know COB & COX cars I was`nt sure how the early ones started as . ie R&P or cam & peg as None of my references actually stated R & P altho` their delivery dates are after 7/3/63  ie csx 2126
   Never read about 2030 and put together what I`ve learn`t from this thread.Most informative and I thank you.

[Flyinghorse]

If we are going to be pedantic,the  "worm"  is technically a helical cam of constant diameter. Worm would be slang surely?
   
   Good piece here from the morgan club,where they note a change from Burman to "Bishop Cam" allegedly due to poor manufacturing quality in the Burman boxes.
   //http://www.morganownersclub.com.au/patent_prattles.htm#Bishop Cam//
   
   A lot of Traction steam engines used rack & pinion steering so it was not a new concept.
   
   Also Citroen used it in the 1937 FWD traction Avant 7CV.
   The Triumph herald used it in 1957.
   
   Quite what the cataylst was for its increasing use in cars in the late 50's & early 60's is not clear. Certainly not likley American as in general they were slow to adopt R&P.
   There may be something in the "feedback" argument from R&P from a racing perspective. From a manufacturing perspective cost is the likely answer-no helical machining.
   The radial tyre was also starting to make an appearance and was perhaps showing up limitations in chassis/steering. I dont know if Cobras had radials to start withm,but it all sounds like solutions to getting that V8 power to good use.
   FH

[ACOCArch]

A logical and well-informed discussion by Robin and Barrie about AC's design, development and engineering practices, which accords with my father's experience of dealing with AC in the 1950s. I would add only that AC often purchased bought-in items in quite large batches by their standards, sometimes 100 off, and this could have been one influence on the timing of introducing some changes.
   
   Just to scotch any notion that rack and pinion was a new idea in the 1950s, rack and pinion systems are as old as engineering. One nice example can be seen on the Snowdon Mountain Railway!
   
   AC used the R&P concept for steering on their first 4-wheeled cars, the Fivet and the Cyclecar, in 1912. This is illustrated in the photo, below, of the steering mechanism on the AC Cyclecar in Moscow. The known surviving Fivet is almost identical.
   
   As can be seen, in this design the steering force is applied from one end of the rack, probably to better accomodate the geometry of a beam axle located by an 'A' frame.
   
   

[rstainer]

Re previous post: 'Simple observation shows that those who race historically correct cars are several seconds a lap slower than the 'why bother with historical accuracy' persuasion.I'd like to illustrate my point with a photo of 2532 (see the register) but the Forum technology defeats me; if anyone emails me the procedure (rstainer@radcothouse.co.uk) I'll post the photo and you'll see a steering assembly (and many other components) unlike any product of AC/Cam Gears or any other 60's supplier.'
   
   Here it is (I hope):
   

[rstainer]

[A-Snake]

quote:Originally posted by rstainer
   

   

   
   Why that looks so well preserved one would
   think it was built yesterday [:o)]