Model history: Ferdinand Porsche moved from Daimler's Austrian subsidiary to company headquarters in Stuttgart to replace Paul Daimler as chief designer in 1922. His first task was to develop a new supercharged engine for Mercedes' top of the range models, which at the time were still powered by big and heavy airplane engines. Following his brief, Porsche created a new six cylinder engine that was available with a displacement of either 4 or 6.3 litre.
The new engines' first application was in big, heavy chassis that really were no match for the powerful 'sixes' in terms of both handling and braking. A racer at heart, Porsche was eager to develop a chassis that his engine more justice. Sadly resources were limited at the time but he did manage to create the 630 K (for Kurz or short). As the name suggested, this combined the largest of the two engine with a shortened version of the chassis that in its original form had been large enough to carry 7-passenger limousine bodies.
Additional funds finally did become available following the merger of Daimler and Benz in 1926. Porsche wasted no time and set about developing a brand new chassis that would do 'his' engine more justice. The new car was based around a pressed-steel ladder frame that kicked up over both the front and rear axle. This allowed for a much lower ride-height than the earlier Mercedes models. The suspension itself was of a conventional design with leaf springs and friction dampers on all four corners. The stopping power was provided by large servo-assisted drum brakes.
For this new application, the straight six was also further developed and enlarged to just shy of 6.8 litre. The sophisticated engine featured an aluminium alloy block with a cast-iron head. A single overhead camshaft was fitted, which driven by a shaft at the rear of the engine. Mounted vertically at the front of the engine was a Roots-type supercharger. This was only engaged when the accelerator pedal was pressed to the floor. It was advised to use the supercharger for no more than 15 seconds for reliability reasons. Once against, it freed up around 180 - 225 bhp depending on the tune of the engine.
Dubbed the 680 S, for Sport, the new Mercedes-Benz debuted at the June 1927 opening race at the Nürburgring. Fitted with a simple four-seater body and a high compression / high boost engine, the 680 S proved a race winner straight out of the box, winning the first ever race at the now legendary circuit as well as the German Grand Prix soon after. The new Mercedes-Benz not only impressed with its undeniable pace but also stood out from the rest of the field thanks to the glorious whine produced once the supercharger was engaged.
Soon after its victorious debut, the 680 S entered series production. It was available with factory or 'Sindelfingen' coachwork or as a rolling chassis ready to receive the custom body of the client's choice. Thanks to the relatively low chassis, the new Mercedes-Benz was a popular subject for the time's finest designers like Jacques Saoutchik. Even with the 'standard' coachwork, the 680 S was a striking machine in part due to the remarkably long engine cover.
By the end of 1928, Mercedes-Benz had produced close to 150 examples of the 680 S. At that time it was replaced by the slightly larger engined 710 SS. Further derivatives include the SSK and SSKL competition cars, which used a shorter chassis. Known as the 'White Elephants', the supercharged range that kicked off with the 680 S ranks among the finest and most desirable produced by Mercedes-Benz.
Ordered new by a retired British army officer, this 680 S was delivered as a rolling chassis to Cadogan Motors ltd. Similar in design to the factory four-seater Tourer bodies, the coachwork created by Cadogan was considerably lighter due to the extensive use of fabric for the skin. The car was completed in the Spring of 1928, the Captain used the car extensively on the road, keeping notes on how the car performed. In around 1931, the standard gearbox was replaced by a more driver friendly Wilson pre-selector gearbox. At around the same time, the Captain also had a special garage made to house the Mercedes.
This has been the home for the unique Cadogan 680 S for over 80 years now. It was taken off the road in 1952 and sat unused on axle stands until 2005. At that point in time, the car was carefully and in great secrecy brought back to life by the original owner's grandson as a 75th birthday present for his father. Marque-expert Alan Hancock did the work, which was mainly limited to general maintenance like a fresh set of tyres and tweaks to the brakes and transmission. Once restarted, the big six cylinder engine ran remarkably well and thanks to the aged exhaust system proved a throaty birthday present. The family has now decided to part with the car and the effectively one owner, highly original Mercedes will be offered in the 2012 Bonhams Revival sale on September 15th. The pre-sale estimate is GBP 1.5 - 2 million.