Taming the cat – Utah gets a hard reboot.
The compact Jaguar saloons were landmark cars for the company and did much to raise the carmaker’s profile and profitability, but in its first generation form it was not a model which Browns Lane engineering staff viewed with terrific pride, owing to a number of significant compromises buried beneath its shapely envelope.
As development progressed upon the more powerful 3.4 litre version, the handling deficiencies consequent to its narrow rear track (acceptable in the lighter, lower powered car, but less so here), forced engineers to investigate ways to mitigate its malign effects. For its 1957 launch, the universal fitment of cut-away rear wheel spats modernised the appearance to some extent, also facilitating the fitment of wire wheels, aiding brake cooling.
But neither Bill Heynes, nor Bob Knight were content. In retrospect, perhaps further development of the sweeter, freer-spinning 2.4 unit by attention to its carburation, valve timing and breathing would have provided similar performance in a less nose-heavy package, but certainly the larger engine was deemed the cheaper, more expedient option, better suited to the American market. The 3.4 was a genuinely fast car, but it was one which required a skilled driver to extract its best at higher speeds.
Further experiments by the factory included the use of offset wheels and wider track widths, the latter being viewed the only really viable solution. Utah Mark 2 therefore came about largely from the engineering department’s determination to place their stamp upon a car which they felt had to some extent had got out from under them.
Hence, a mere four years after its debut, the car received a major overhaul; the changes being sufficiently comprehensive that while it was not strictly classed as a new model, it went a good way further than a facelift. Nevertheless, some legacy issues were not only retained, but were exacerbated by the extra weight gained in fittings and equipment, not to mention the heavier new 3.8 litre engine powering topline models.
But while the front-biased weight distribution could not be altered without significant changes to the structure, Knight and his fellow engineers focused their attention upon mitigating its effects. One significant finding saw the front suspension roll centre increased by 4″, brought about by inclining the front wishbones downwards, while increasing the distance between top and bottom balljoints.
This necessitated a longer wishbone, which also had the effect of reducing the swivel inclination of the steering, tightening up body control notably, while improving steering response. These changes, in conjunction with a 2″ increase in rear track made for a better behaved, more responsive car, especially in its more powerful forms. The heavy low-geared steering remained a notable bugbear however.
While Bill Heynes was putting his stamp on the Mark 2’s chassis, Sir William Lyons did likewise with the styling, in particular the restrictive outward visibility imposed by the original body design. Now that it was known where the major stresses of the Utah body were centred, the imposing screen pillars could be dispensed with. Lyons took an existing experimental Mark One body and literally marked up the new daylight openings with a yellow tyre crayon for Fred Gardiner and his tinnies to decipher.
Visual changes were largely confined to the canopy, where the larger glass area lent the car a far lighter appearance, not to mention vastly better visibility for both driver and passengers alike. Less obvious however was the reduction of the earlier car’s tapered rear-end, lending the Mark 2’s posterior a slightly heavier look.
In order to save time, Jaguar’s body technicians prepared no drawings for Pressed Steel Fisher to work from in devising the revised body tooling, simply providing a Utah bodyshell with a block of wood wedged into the rear wheelarch to illustrate the intended clearance. PSF, quite understandably were horrified, warning Browns Lane never to pull a stunt like that again.
But Jaguar being Jaguar, everything was done on the back of an envelope, and as the first cars were coming off the tracks, pavé testing at MIRA (which was still ongoing) threw up a potentially dangerous fault. As experimental cars fitted with the revised front suspension continued to pound the unforgiving Lindley cobblestones, cracks repeatedly appeared on the new-design upper wishbones, which eventually failed entirely. The car simply could not go on sale like this.
Having hurriedly lashed up a strengthened wishbone in experimental, it now fell upon Jaguar’s proving chief, Norman Dewis to put the requisite 1000 miles on a modified prototype. Driving non-stop on MIRA’s notorious pave over the weekend in atrocious weather conditions, with just two apprentices in support, they just managed it – the strengthened wishbone surviving the ordeal, ensuring that production could continue. Finished cars or those still on the tracks received strengthened parts, with the modified production wishbones being retrofitted under warranty.
It was a fortuitous escape, because the financial and reputational harm a suspension of production would have incurred at that point would have been quite damaging, especially with interest in the new car being so high. But this didn’t mean that Mark 2 owners didn’t feel the effects of Jaguar’s often casual approach to quality control. Having taken a well-fettled press car home one evening, Sir William reported back to his engineering chief that “on an indifferent piece of road”, the Mark 2 “sounds like it was falling to pieces”. Subsequent investigation determined that in places spot welding carried out by PSF on Mark 2 bodies could be as much as 60% short of specification.
The Mark 2 also benefited from further experiments carried out by Bob Knight on noise elimination. Having carried out extensive soundproofing behind the dash area of a prototype 3.4, Knight offered the prototype to Lyons to sample. Highly impressed, Jaguar’s boss insisted it become standard specification immediately, arranging for the felt to be shipped to Browns Lane on trucks the same night. Often portrayed as tight-fisted, Sir William neither skimped, nor hesitated when he recognised a clear commercial advantage.
So, while the first generation of compact Jaguars could reasonably be described as something of a flawed gem, its Mark 2 iteration proved to be a good deal more than a simple polishing exercise.
5 thoughts on “State of Revision”
What a great story of British “garden shed” engineering! It speaks volumes of the skills and talent of those involved that they could have achieved so much by taking an intuitive rather than strictly scientific approach to the development.
Eóin’s piece has encouraged me to look properly at photographs of the Mk1 and Mk2. I won’t preempt the next instalment except to suggest that this must count as one of the most successful revisions ever, both in asthetic and commercial terms. It was on a par with the XJ Series II to Series III transformation, which was also, of course, an above the waistline job.
I was never totally convinced by the Mk 2.
The double chrome B post split the car in half vertically.
There were two cars here, posing as one:
1. A luxury saloon — with white-wall tyres.
2. A sports-racing car, with wire wheels. This latter incarnation went on to track success with Parkes and Salvadori, the former with non-standard front hub carriers!
The Flaminia, a bigger car, often matched them for reliability in races, but, being rarer, were not developed as much as the Jaguars, so have faded from today’s retro competitions.
“Now that it was known where the major stresses of the Utah body were centred, the imposing screen pillars could be dispensed with.”
This would have been one of the real problems in the pre-computer days with unit bodies. Until you actually built a prototype hull to test, even the load carrying behavior would not be accurately known.
For pre computer hand calculations, traditional frames or even truss space frames like the 300sl would have been a lot easier to deal with. Also, it’s a lot easier and less expensive to build a prototype frame or space frame and test it.
Yes, I imagine it cost very little for Maserati to build its Birdcage just by adding a tube at a time until two heavy blokes sitting on it didn’t bend it.
Of course, MB would never have done that, and the 300SL frame looks very well organised.
It all sounds a bit by guess and by golly, those suspension mods. If you follow eng-tips suspension forum where minutiae of Milliken chassis analysis are examined in detail, the consensus is that a narrow rear track tends towards oversteer, all other things being equal. So widening it a bit will promote understeer, and those front suspension mods seem to be in the same direction by raising the static roll centre height and reducing the kingpin inclination. Was the original 2.4 Utah an oversteering little devil? Of course, before real mathematical analysis of suspensions had been developed, it was all a bit rule of thumb except perhaps for Maurice Olley’s thoughts, although the C-type rear suspension was rather neat in cancelling out driveline torque and Utah seems to have some of that. I mean, Mercedes beat its brains out for two decades trying to make rear swing axles work, low pivot or not, when a decent stick axle would have been better, and Jag’s independent rear put Mercedes in the shade all around. Then BMW persisted with those awful rear swing arm rear axles for years as well, really nasty stuff.
But it was still all a bit amateur hour at jaguar in the 1950s the way it’s described, and Dunlop C41 tires of the era would be laughed off stage these days. Interesting how we’ve advanced from a slippers, pipe and baccy sit down with a nice cup of tea approximate calculations to more precision. Those body mods by tire crayon for PSF really sound like something professional engineers wouldn’t do. Knight seems to have been a whiz on active NVH reduction though, except again, you have to wonder on the passive sound-deadening felt. Detroit had been ladling that stuff into higher-end cars for some time, and there were adverts for DIY kits in the 1960s, so it wasn’t much of a secret how to go about things. And stick on Bostik panels with glue that only worked (stuck that is) for any length of time in the UK environment were available as well.
How much more did the extra inch or thereabouts of engine block height for the 3.4 compared to the 2.4 actually weigh? Can’t see why the 3.8 weighed even more, but who knows how they went about the 4 mm bore increase with the same exterior dimensions. All 3 litre or more iron sixes of that era weighed an absolute ton, or near enough 700 lbs anyway. Ford led the way on thinwall iron casting in the early 1960s with the 221/260/289/302 V8, and a fully dressed engine weighs only about 500 lbs even with iron intake and exhaust manifolds, and it comes naturally as a crossflow. How the Essex in particular and Cologne V6’s weighed so much following that must have been a case of Ford not transferring its tech to its European operations.
Fascinating stuff on the Utah. Timeless styling that didn’t age badly at all. But wide whitewalls on a Jag of that vintage just look so wrong to me. Ugh.
Good stuff, Mr Doyle.