DS-inspired prototype that spawned the Mini 1 ½-litre saloon BMC XC9001

Mini 1 ½-litre saloon BMC XC9001

The DS-inspired prototype that spawned the Mini. BMC’s abandoned future Issigonis’ forgotten XC9001 project. After the stillborn V8 he had designed for Alvis, and before the Mini, Alec Issigonis created a reardrive 1 ½ -litre saloon for BMC. Jon Pressnell tells the fascinating inside story of the XC9001 prototype. Photography Bmiht/Author’s Collection/Jan Simmons/Suzanne Hankey.

Issigonis managed project with small team. Below: full-sized mock-up outside Longbridge admin block. Neat lines of Mini are obvious in the profile.

Alec Issigonis didn’t hang around. Having returned to BMC in December 1955, as deputy engineering director, he was soon sketching new designs, exploring ideas for the corporation’s next generation of small, medium and large cars. Perhaps surprisingly, for someone who admitted that he had little interest in bigger vehicles, the first model to make the transition from sketchbook to reality was not the smallest of the family of cars he envisaged, but the largest.

This was code-named XC9001, and had it reached production it would have in effect replaced the Austin Cambridge and Morris Oxford. In engineering and in styling, XC9001 bridged the creative gap between the Alvis V8 and the Mini, drawing on the Alvis while offering clues as to how the Mini – originally XC9003 – would emerge, fewer than four years later.

Indeed, in many ways XC9001 was a shrunken Alvis V8. Stylistically it was not dissimilar, and it had the same long wheelbase. It also continued as a rolling laboratory for Alex Moulton’s rubber-and-fluid suspension, first tried, in a very rudimentary form, on the Alvis. Even the engine was derived from the Alvis unit. It’s a car that’s always fascinated me, and over the past three decades I have interviewed the key players in the project. They’re all no longer with us, but at least the story can be fully told, thanks to their recollections, and to the Issigonis notebooks surviving at the British Motor Industry Heritage Trust.

“XC9001 took one year to do,” according to body draughtsman John Sheppard, a former member of the Alvis V8 team, whom Issigonis had persuaded to join him over at Longbridge. “I started in January 1956 and by the end of the year we’d got the car made – we built just the one. I was absolutely flabbergasted by the efficiency of the Experimental Department bodyshop. It was an eye-opener for me. We had chaps in the shop who could interpret drawings so well. It was a brilliant department. I drew the thing – taking Issi’s sketches, cleaning the lines up – and we had a little quarter-scale model made. At first it was just the Old Chap and myself, and two ordinary drawing boards with T-squares. He had one and I had the other. He did all of the mechanicals and left me to do the bodywork.”

Described as “pretty plain” and “typical Issigonis” by Doug Adams, the future head of the Experimental Department bodyshop, the original mock-up clearly hints at the Mini, not least in its rounded rear and in the shape of the radiator grille. Observing in one of his notepads that ‘simple shapes if well balanced last longer’, Issigonis was leaving behind the consciously ‘styled’ look of the Morris Minor in favour of a form-follows-function approach. ‘[The] basic envelope is governed by engineering,’ he wrote. ‘If this is not right no amount of additional styling will put things right.’

As with the Alvis, there were pronounced mouldings around the wheelarches and sills, but unlike the Alvis these were part of the side panels rather than being bolted in place. An elegant detail is the way the round tail-lights are ‘frenched’ – sitting in neat circular chromeembellished recesses. When it was built for real, the rear of the car was further cleaned-up, according to Sheppard, by the hinges for the bottom-pivoted bootlid being concealed within the bumper over-riders. “I said to Issigonis that if anyone bumped the over-riders, you wouldn’t be able to get into the boot,” he recalled in 2015.

In stance there is something of the Citroen DS about the car, which as built had a monocoque body with – or so it seems – one-piece sides. “For quite a while, and from pretty early on, Issigonis had use of a DS,” Sheppard once told me. “He ran it for several months, I’d guess, and thought it marvellous.” He confirmed that the Citroën influenced several details on XC9001. Firstly, there was a bolt-on glassfibre roof, and secondly, the door hinges were directly copied from the threaded fully adjustable items of the DS. Sheppard also recalled experimenting with a bolt-on rear wing secured at its forward edge by two prongs – just as on the Citroën.

The wheelbase was a key factor in XC9001 not being front-wheel-drive, despite early sketches showing FWD installations incorporating a flat-four ahead of the axle line and a narrow-angle V4 mounted transversely. In his notepads of the time, Issigonis wrote of how a long wheelbase was necessary for Moulton’s interconnected suspension to work effectively and that this called for large front-wheel steering angles. ‘This puts FWD in an impossible position,’ he wrote. This wasn’t necessarily true, but having not arrived at his transverse-engine layout he wasn’t prepared to compromise internal packaging by solving the problem via a spaceinefficient in-line front-drive installation. In any case, he was happy to record that the long wheelbase would allow BMC to offer a ‘new look’ in car design, as well as promoting stable roadholding and maximum internal accommodation.

Packaging was indeed one of the key tenets of XC9001’s design remembered by Sheppard: “It was exactly the size of a Morris Minor. It was a five-seater, 12ft long and maybe 60in wide. I was running a Minor at the time, and Issigonis asked me to bring it up to the styling studio so they could see how much room we could get into a car the length and width of the Morris.”

If XC9001 eschewed front drive, Issigonis still sought unconventional transmission solutions, but members of the team had hazy recollections of the exact configuration. “I seem to remember a split propshaft to an independent rear,” recalled Jack Daniels, right-hand man to Issigonis, in 1999. “We certainly had difficulty with the propshaft.

I’ve got a suspicion that the gearbox was at one time up on a crossmember fairly near the engine, with a short shaft connected. Another time I think we simply put a split propshaft in, and probably the gearbox was then at the back. I certainly worked on a complete gearbox and what-have-you at the back.”

This tallies with the memories of Moulton – and of Chris Kingham, another member of the Alvis V8 team who joined Issigonis at BMC during 1956. “I have a feeling the gearbox was at the rear end, because we had problems with a long propshaft, which we had difficulty balancing,” Kingham said when we spoke back in 1998.

Pulling this together, it seems likely that both a central gearbox and a ’box at the rear, in unit with the axle, were tried, the latter layout having been found on the Alvis. According to Kingham, who went on to design the Mini transmission, the geartrain would almost certainly have been a standard BMC four-speed set-up, and he had memories – as did Daniels – of a Smiths electromagnetic clutch being used. As with the engine, aluminium seems to have been used for the gearbox and axle casings, to keep down weight.

Sketches by Issigonis show both a central gearbox and one in-unit with the back axle. In one notebook there is also an outline specification of the car. The section on the transmission reads ‘Gearbox location should be between front seats to avoid complicated control shift problems’.

This meant linking the engine to the ’box by a tube extension, and there was reference to use of a rubber coupling, in order to suppress vibration. Emphasising how the various elements of the design were intended to work together, Issigonis observed that the central gearbox and ‘central passenger loading’ would offer nearly 50:50 weight distribution and ‘minimise trim changes with interconnected suspension’. However, a later notebook has an entry reading ‘Gearbox dismantled to find cause of howl noise in neutral and noisy final drive’ – proof, surely, that at this stage a transaxle was being tried. Elsewhere there is mention of the option of two-pedal Manumatic transmission – in other words, the ill-loved Smiths electromagnetic set-up.

As for the engine, according to Kingham it was “half of the alloy V8 engine that we did at Alvis – although at 1½ litres, it was in fact slightly down on half of the 3½-litre Alvis unit – and it had skew drive to a single overhead camshaft. There were wet liners and three main bearings”.

Another detail was recalled by Daniels: “The flywheel itself was the generator. I remember that it was no bloody good. Well, it partly worked.” In all this, memories consistently were of an engine with disappointing performance, incapable of pulling the skin off that clichéd rice pudding. “It couldn’t, at least at first,” Daniels was able to confirm. “We never spent much time on it. It was there, that was all.”

Corroboration that the engine was down on performance comes from one of the notebooks, in which there is mention of a power output of just 33bhp on a single SU carb. At the time, the 1489cc B-series in the Austin Cambridge developed 50bhp, so clearly something wasn’t as it should have been. Maybe, despite acknowledging in an aide-mémoire that the car needed to weigh less and have more power, Issigonis wasn’t as bothered as he should have been, providing the engine met his criteria – laid down in one of the notebooks – of offering economy and a long life. “He wasn’t a person who knew anything much about engines at all,” former Motor editor Charles Bulmer once remarked to me. “He didn’t claim to be an engine man.”

Issigonis was in fact far more interested in the suspension of XC9001, and in his blossoming collaboration with Moulton, sealed in May ’1956 by a tripartite agreement between BMC, Moulton and Dunlop. The fluid-and-rubber system used on the Alvis had been relatively crude, with two conical rubber units joined together at each wheel and filled with fluid, and a simple copper tube providing front-to-rear interconnection. For XC9001, this arrangement gave way to a pair of centrally positioned rubber-and-fluid springing units – called ‘cheeses’ by Moulton.

The suspension used a triangulated wishbonelike arrangement at the front, as far as can be ascertained, while the independent rear set-up used two lower arms to give a semi-trailing layout – in conjunction with Moulton rubber joints for the driveshafts. It seems that there were anti-roll bars at both front and rear, despite which an unstable transition to oversteer in high-speed bends was to remain a concern.

“Most of the time we were working on the suspension side,” Daniels admitted. “Our first shot was a canister of about 8-10in diameter, like a big frying pan, wide but not very deep, with a rubber element in it, and we mounted it solidly onto the floor, one per side,” he told me, evidently referring to the Moulton ‘cheeses’.

“There was a rubber-diaphragm displacer at each wheel, pushing the water into this one canister, big enough to take the suspension movement from front to rear. It worked, but there was a very pronounced hydraulic lock – a ‘bonk’ almost. We didn’t know how to suppress that, and it sounded worse because it came up through the floor. So we dumped it.”

Moulton conceded in a 1992 interview that he was very much feeling his way. “In those times we were very fundamental and not scientific,” he confessed, recalling various experiments with fluid-suspended Minors that were concurrent with XC9001. During 1957 the ‘cheeses’ were briefly replaced by ‘flying-saucer’ gas springs, but whether these were tried on XC9001 is not clear. According to Daniels, in any case, the next move was to front-to-rear rubber piping.

He added: “We then tried a full-length sausage from the front to the rear – a rubber thing almost like a gear wheel on the outside – more like a spline – and all wrapped up in a cotton or nylon covering. That was tucked inside the sill. The trouble was that, despite all the bindings around the outside, it expanded end-wise as much as the other way, and there were bits of rubber thrashing around in the sills. You could hear it going ‘clump clump’ all the time. It rode quite passably, but it wasn’t really an improvement.”

The piping was called the Python – “because it seemed to be alive,” according to Moulton. “When a Minor with the system was being driven down to Issigonis and myself in Monte-Carlo, it had to be tamed by being tied up with wire from a wine cask. It gave a very floaty ride, but it was wonderfully flat and comfortable.”

The first test runs of XC9001 outside the factory took place in February 1957. Notes by Issigonis confirm that suspension harshness was a continuing problem, as was high-speed rolloversteer – although one note records the rear-seat ride as being better than that of an Austin A55. At one stage a pneumatic element was introduced into the system, but this made no worthwhile improvement. Another recurring issue was boom and roughness from the engine.   ‘Car is still coarse and noisy even though rear end has been sound-damped,’ wrote Issigonis in March 1957, after his eighth sortie in the vehicle.

One of the last references is to XC9001 being tested at Chalgrove airfield in August that year. By that time Issigonis and his small team were concentrating full-time on pushing the Mini forward, following BMC boss Leonard Lord’s well-documented trial run in the first prototype, on 19 July. XC9001 probably remained ‘live’ until about September, but from the moment that the Suez Crisis had kicked in, at the very end of 1956, the project had been overtaken by the pressing need to develop a small economy car.

From then, the main value of XC9001 was as a testbed for Moulton’s fluid-based suspension, which both he and Issigonis initially hoped could be used on the Mini. This wasn’t to be, because it wasn’t until August 1959 that Moulton Developments would arrive at a satisfactory prototype unit, suitable for manufacture under the Hydrolastic name. But the process of experimentation on XC9001 helped to form Alex Moulton’s ideas – and ultimately 11 million or so cars would be fitted with his springing. For that alone, the project deserves a modest place in history.

BMC- XC9001

Alvis V8’s styling and running gear informed design of car. Below: scale model of an early proposal for the large saloon has something of the Series II Oxford about it, but with less fussy detailing. Issigonis sketch shows the mechanical configuration; note central gearbox and interconnected Moulton suspension. Right: John Sheppard (on left) and Jack Daniels, probably at around XC9001 time.

BMC- XC9001

Issigonis with the sole prototype, probably testing at Chalgrove airfield in late 1957 – by which time the Mini had become the main priority. Left the revolutionary Citroën DS very much influenced Issigonis. Elements, such as GRP roof and adjustable door hinges, appeared on the XC9001. Below: a DS-like sketch done by Issigonis. From top: Mini mock-up featured the same black-over- red colour scheme – an ‘Issi’ favourite; XC9001 was intended to have the same envelope as Minor.

BMC- XC9001

Left: mock-up of smaller XC9002, the future 1100, with that for the XC9001. Below: Farina proposed sharper styling, similar in appearance to the 1100. From right: re-started and re-orientated, the project ultimately became 1800; meanwhile, BMC launched a range of conventional Farina-styled mid-sizers (here an Oxford Series V).



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