Press Release
The presentation on 5th March 1955 was appropriate to the event. Without pomp and ceremony, but filled with quiet pride, the top management of BMW unveiled their latest product before the assembled press. In the opulent lakeside Hotel Bachmair in Rottach-Egern, the journalists were shown a two-seater, but one which was unlike any sports car. The configuration of the new BMW was something quite different. Fritz Fiedler, then BMW’s Head of Vehicle Development, summed it up in his opening speech: “With the BMW Isetta Motocoupé, the public are being offered an economical type of car and a concept that is quite novel in Germany.” Indeed, no vehicle like it had been seen before on German roads: a tiny, almost spherical car with windows all round – and a single door at the front.
Admittedly, the latest BMW hardly came as a surprise. The company had announced its new model back in the autumn of 1954, and six months prior to that the Isetta had been available for inspection for the first time at the factory in Milbertshofen. In the early 1950s, the Bayerische Motoren Werke were still suffering from the after-effects of the Second World War. True, in 1948 motorcycle production had been resumed with great success. Up until 1954 sales of the single- and twin-cylinder machines with shaft drive soared upwards. Nevertheless, it quickly became clear to the market strategists that the two-wheeler was only the first rung on the mobility ladder and the desire for a weatherproof vehicle was their customers’ prime consideration. With the big 501 Saloon, which had a pre-war six-cylinder engine under the bonnet, BMW was certainly offering a fast and luxurious car; but for a large part of the population it was several times too expensive. The company had no alternative to offer, since the resumption of car production after the war had been made extremely difficult by the loss of the Eisenach car plant. Production facilities as well as skilled staff had to be replaced. Not until the Frankfurt Motor Show in 1951 was the BMW 501 put on the road as the company’s first post-war car. The prestigious and extravagantly engineered saloon had even been improved by fitting it with the world’s first light-alloy eight-cylinder engine in time for the 1954 Geneva Motor Show, but the volume needed for profitable production could not be achieved.
1954 Turin Motor Show: BMW meets Iso.
At the beginning of 1954, shortly after the Board of BMW had proudly presented the new V8 on the shores of Lake Geneva, BMW’s main agent in Switzerland, C.A. Drenowatz, was visiting the Geneva Show when he discovered a “fully-faired motorcycle” called an Isetta and manufactured by the Italian firm Isomoto. He immediately reported his findings to the head of sales, Hanns Grewenig. Since BMW’s top management had already spent a lot of time thinking about a popular car that would represent the best possible value for money, they dispatched Eberhard Wolff, who headed the test division, to the Turin Motor Show which was held in late April and where Iso was again showing its Isetta to the public. There were two prime considerations: it was essential that the Isetta could be put into production a) quickly and b) at no great cost.
The first thing that struck one about the Isetta was its shape. Yet the “egg on wheels”, as the little vehicle was described right from the start, was remarkable not only for its unique profile, but also for its unusual technical features. For instance, the whole of the front end could be opened outwards – not even luxury saloons offered such a spacious method of boarding. The steering wheel and instrument panel were fixed to this door, which extended across the whole width of the car. A universal joint, which split the steering column a few centimetres above the floor panel, enabled one to move the steering column forward as well. Thus the driver and passenger merely had to clamber over the fixed foot pedals and could settle onto the two-seater bench without any contortions. Behind the seat was a generous space for the spare wheel and, if necessary, luggage. To the rear of the occupants puttered the heart of the little Italian job, a two-stroke engine with twin cylinders, which had a capacity of 236 cc and could deliver 9.5 horsepower.
BMW buys the name and the tooling along with it.
Wolff recognized that the simple and relatively easy-to-produce design of the microcar had exactly the potential that BMW was looking for. Even before the exhibition closed its doors, he got in touch with the head of Iso, Renzo Rivolta, who was already extremely interested in doing licensing deals. A partner with such a great name as BMW, moreover, seemed like a godsend. His offer was attractive: BMW could take over both the name and principal tooling for the bodywork. The BMW Board wasted little time and the then Technical Director, Kurt Donath, and Head of Development, Fritz Fiedler, drove to Milan to get down to brass tacks with Iso.
The Isetta: “It is deliberately not intended to be a saloon car…”
Almost exactly one year later, the BMW Isetta was launched. Many visual and technical details of the Italian original had been modified and improved by BMW. A first glance showed the bodywork had been altered by having detached headlights fitted at the top of the front-opening door instead of the bottom, and by giving it a new engine cover. In practical terms, Fritz Fiedler had no difficulty in justifying BMW’s bold decision in favour of the Isetta to the assembled trade journalists. In order to bring down the retail price, he said, many manufacturers would previously have tried to save costs in two ways: “Some of them want to achieve this objective by a nitpicking reduction of all the dimensions, following the simplistic calculation made by a lot of people that a hundredweight of car costs so much. The other method of getting the price down is crudeness. In extreme cases I picture the design as a tubular rod, to which some road wheels are attached which are steered by handlebars.” This kind of steering – others called it a joystick – was found, for example, in the Messerschmitt “cabin scooter”. “Between these two extremes,” Fiedler went on, “we now have the BMW Isetta. It is deliberately not intended to be a saloon car, but it is more than something to get you from A to B. It gives its occupants complete protection against the weather; you can get into it with greater ease than many a big car, and it can be driven with such supreme safety that even inept drivers put neither themselves nor others at risk.”
The Isetta’s five trump cards.
Fiedler summed up the advantages of the Isetta in five bullet points:
“1. The cost of the bodywork is decisively influenced by the number of doors. You can get by with one door. The door is not hung in the outer skin of the bodywork, but stands proud of the front end and hence is accident-proof.
2. Three wheels may be cheaper, but they are not nearly as good as four. Putting the drive through a single rear wheel overstrains it. That’s why we opted for two rear wheels. The narrow wheelbase saves us fitting a differential and means that one brake is enough.
3. It has been possible to locate the engine in front of the rear axle, achieving an ideal weight distribution.
4. Thanks to a transverse double cardan shaft, the suspension of the axle and the engine is independent.
5. The egglike shape of the body is taken from nature. It requires least expenditure on materials to enclose a given interior space.”
This catalogue contained numerous BMW ground rules which still apply today – passive and active safety, optimum distribution of axle weight, driving comfort. And there was something else in the new “Motocoupé” – a BMW engine. The original noisy and underpowered two-stroke had already been available at the time of the negotiations between the BMW Board and Renzo Rivolta. If the bodywork was to be bought in, at least BMW could supply its own power unit. And anyway, in Munich there was a proven, reliable and perfectly suited power source: the single-cylinder engine of the BMW R25/3 motorcycle.
A tried and tested motorcycle engine for the new Motocoupé: the single-cylinder 250.
This vehicle set new standards in its class: from a cylinder capacity of 245 cc the single-cylinder generated 12 horsepower at 5,800 rpm. Its construction was as robust as it was simple. The crankcase and cylinder were made of cast iron, the cylinder head of aluminium. However, the head was rotated by 180 degrees compared with the motorcycle engine. The twin-bearing crankshaft was also different in the Isetta power unit, being larger and featuring reinforced bearings. One of the reasons for this was the heavy Dynastart unit which combined the dynamo and self-starter. The laterally located camshaft was driven by a roller chain, and transmitted its control impulses via pushrods into the cylinder head, where the overhead V-shaped valves were activated by rocker arms. The fuel mixture was provided by a Bing sliding carburettor. In addition to further changes of detail, the BMW engineers enlarged the sump for installation in the car and cooled the engine by means of a radial fan.
Economic motoring: top speed of 85 km/h (53 mph) and around 80 mpg.
To quote from a press release at the time of the launch: the engine “gives the BMW Isetta excellent acceleration, with help from the well-chosen ratios in its four-speed gearbox, which also has a claw shift and reverse gear. Gradients of up to 32% can be surmounted with ease. Fuel consumption is as little as 3.8l/100 km (approx. 80 mpg). The maximum speed of 85 km/h (53 mph) can be exploited without anxiety in view of the hydraulic brakes on all four wheels.” With this braking system the Isetta set new standards in the “bubble car” class, since the competition were still fitting cable brakes as standard. Incidentally, the braking arrangement was as follows: each of the front and rear wheels had a drum brake. Admittedly, only the left rear drum was connected to the hydraulic circuit of the service brake. The right-hand drum was connected by a cable to the handbrake lever, which stuck up vertically by the driver’s foot. And in the mid-1950s, by no means every car could boast four forward gears. With a torque of only 14.2 Newton metres at 4,500 revs those gears were sorely needed, even though with a full tank the Isetta only tipped the scales at 360 kg.
Safe roadholding despite a short rear axle.
Initially the wheelbase layout aroused deep suspicion. The two front wheels were mounted at each corner, 120 cm apart, whereas the two rear wheels were tucked in centrally with a track of just 52 cm, making the “darning ball”, as the diminutive car was sometimes dubbed, look like a three-wheeler. The power train from the four-speed gearbox to these two wheels was unusual enough: fixed to the gearbox output drive was something called a Hardy disc, which was a cardan joint made of rubber. On the other side of it was a cardan shaft, and finally a second Hardy disc, which in turn was located at the entrance to a chain case. A duplex chain running in an oil bath led finally to a rigid shaft, at each end of which were the two rear wheels. Thanks to this elaborate power transfer, the engine-gearbox unit was both free of tension and well soundproofed in its linkage to the rear axle. This paid off in terms of a surprisingly comfortable drive and very well-balanced roadholding.
Yet at this point no journalist, let alone a customer, had ever driven the Isetta. Development boss Fritz Fiedler anticipated the scepticism and tackled it head on: “There will probably be heated arguments among experts and laymen about the rigid, uncompensated rear axle with a track significantly narrower than the front one. But there is nothing new about this. These vehicles are said to perform particularly well in hill-climbs on bad and winding roads. We found exactly the same thing in our test drives. No-one who hasn’t seen it for himself can believe how well and how safely this vehicle handles.”
