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Designing the Biggest small car M.I.N.I.

If the British Motor Corporation had set out to design and build a sporty little coupe with superb handling, it is doubtful if they would have come up with anything like the Mini. Instead their design brief was to build the largest car possible using the smallest amount of materials and budget. In 1956 the British motor industry was in a period of recovery after the war when the Suez crisis struck. Once again Britain suffered oil shortages requiring severe petrol rationing. The need for a small economical car was never more apparent.

In the late 1940's Sir Alec Issigonis, while working for Morris, designed the Morris Minor. This car was to become the first British car to sell over a million. Later Sir Alec joined Alvis and worked on designing a big 3.5 litre V8 sports saloon. It was during this project that Sir Alec further developed his ideas for hydrolastic suspension from his early work with single seater racing cars. In 1955, before the car went into production, the project was cancelled and Sir Alec was given a month's notice. The newly formed BMC eagerly hired Sir Alec and two of his design team, Chris Kingham and John Sheppard. In 1957 Sir Alec was given the task of heading a design team of eight to develop the new car. He was given a very small budget and an even smaller time frame, the car had to be in production within two years.

Sir Alec's ideal was to build a people's car suitable for the everyday worker. The goal was to have a car about ten feet long, four feet high, four feet wide and that could carry four average sized adults at a reasonable speed. The size of the car ruled out the traditional layout of an engine at the front driving the rear wheels. Both Volkswagon and Fiat were successfully producing rear engined cars. From his racing experience, Sir Alec was aware of how unstable this layout was at high speed, especially in crosswinds where the rear weight distribution would cause the car to veer off course. Front wheel drive was not uncommon at that time as it featured in a number of Citroens.

Design Sketch
An early sketch of Sir Alec's design shows the side mounted radiator and petrol tank located behind the engine

The small car's design dictated a small engine. Tests were conducted with a two cylinder engine, but it was far too rough and gutless. A larger engine was needed. With limited time and budget a new engine design was out of the question, an existing four cylinder engine would have to be used. With minor modifications BMC's A Series engine could be adapted. This engine, which had powered such cars as the Morris Minor, Austin A30 and Austin Healey Sprite, was a fairly old design and it's inclusion in the Mini's design was only intended as a stopgap measure - something radically better would be designed when there was time.

Now that the engine had been decided upon the problem was how to fit it in the car. Fitting the engine in the traditional North South orientation presented two problems. First it would require about five feet of engine bay - not very good in a ten foot long car!. Secondly the engine would have to overhang the front wheels by a least two feet to accommodate the front wheel drive transmission - again not good in a ten foot long car.

The only way to solve these problems was to turn the engine sideways. This was a radial departure from car design at the time but it still presented one problem. The engine with transmission bolted on the back (or now the side) was about five feet wide and would not possibly fit between the wheels of a four foot wide car. Sir Alec came up with the radical solution of putting the gearbox in the sump under the engine. This compact engine and transmission package fitted neatly (only just) into the space available and was an unique engineering solution for that time.

Sir Alec's work with Alex Moulton on rubber cone suspension had been quite successful at Alvis. The system's small space requirements made it ideal for use in the Mini. The need to maximise space in the boot meant that a simple beam axle was not feasible for the rear. Sir Alec designed a simple trailing arm suspension that proved highly successful. The Mini was one of the first cars with four wheel independent suspension and set new standards in road holding. Space constraints also dictated the use of rack and pinion steering, then only found in exotic sports cars.

The effective suspension system was essential to compensate for the harder ride given by the inevitably small tyres. Sir Alec initially demanded wheel rims of only eight inches but, when it was pointed out by the horrified engineers that there would be no room for the brakes, he compromised on ten inches. The small tyres also presented problems with high temperatures and wear. Reports were being received from Germany of the problems experienced on the new motorways by bubble cars which were always blowing tyres. Dunlop, who had a close working relationship with BMC, took up the challenge of developing a suitable tyre.

The monocoque design of the body shell was another unique feature, as most cars at the time still had separate chassis and body. There was so little money available that they couldn't afford to build the body up on jigs, which is why Minis have external seams. The external seams allowed the body to be spot welded together without the aid of a jig. When it came to the body styling, Sir Alec was just plain practical. When asked by the Italian designer, Sergio Farina, if he could restyle the Mini, Sir Alec replied "Look at your cars, they're like women's clothes - out of date in two years. My car will still be in fashion after I've gone."

 

Engine Cutaway
A cutaway of the Mini's A series engine and transmission

 

During testing the engine continued to give trouble. Oil leaking from the primary gear caused the clutch to slip and the carburettor, which was positioned at the front of the car in the prototype, was prone to icing up. Sir Alec solved the carburettor problem by turning the engine around 180 degrees and tucking the carburettor behind the block and above the exhaust - a radical solution only months before the release. Unfortunately it didn't rain much during the testing so no-one realised how susceptible the distributor would be to water. The clutch problem wasn't really solved until after the car had been released.

The car was launched on 26 August 1959 through both Austin and Morris franchises around the world. It was priced at 496, which was about the same price as the (wrongly named) Ford Popular, and nearly 100 cheaper than the Ford Anglia, neither of which had the speed, handling or advanced technology of the Mini.

After it's release only a few minor problems were experienced including leaking floor sills and the exposed distributor. All in all the Mini was relatively untroubled considering it's untried technology. Unfortunately the working class, for whom Sir Alec had primarily designed the car for, were not taken by this little box on wheels with all its technical innovations.

engine2.jpg (14044 bytes)
Pre-production engine layout

The people it did interest though were the tuners and racers. To them the Mini was a small low box with a wheel at each corner, superb handling with rack and pinion steering, and used an engine that they were experienced with. The most prominent of these people was of course John Cooper, the Formula One car constructor. Two of his drivers, Jack Brabham and Bruce McLaren, drove Minis on the road and were wildly enthusiastic about them. John Cooper knew all about tuning the A Series engine and he discussed with Sir Alec the idea of building a special. Sir Alec was still locked into the idea that the Mini was an everyman's car and resisted the idea. Finally Cooper went to the then BMC chairman, George Harriman to ask if he could build a run of four seater GTs. After a brief meeting Harriman agreed to a trial run of 1000 cars. The deal, whereby Cooper received a 2 royalty per car for research and development, was settled on a handshake.

Cooper enlarged the engine capacity to 997cc and fitted twin SU carburettors and a three branch exhaust manifold. The engine was strengthened to cope with the 55bhp output. The gearbox saw altered gear ratios and a remote gear change fitted - a vast improvement from the 'magic wand' gear change of the early Mini. Top speed was a thrilling 85mph.

By far the biggest enhancement was to the brakes. Lockheed took up the challenge of producing a set of seven inch disk brakes that fitted inside the ten inch wheels. It was regarded as a technological marvel to get disk brakes on such a small car.

The first Mini Cooper was release in October 1961, just two years after the launch of the original car. Badged in both Morris and Austin marquees, Morris Coopers always outsold Austin ones. Over the next 10 years nearly 145,000 Mini Coopers were to be made.

by Dean Cording

 

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