Tuesday, 27 June 2017

The Development of the DKW F9

On 25 January 1935, director of sales, Dr Carl Hahn, addressed a meeting of the Auto Union board. “In my opinion, with today’s models, we can no longer be competitive in the long term. Fundamentally we will have to create new models that, right from the start, are designed for lower cost.”

Since his earliest days in J S Rasmussen and Co’s DKW, Dr Hahn had actively sought feedback from the company’s dealer network and was closely attuned to the ‘word on the street.’ DKW had made its name in the budget car market with its Front series of two-stroke motored light cars. However, in recent times DKW’s position had been steadily eroding against competition from more modern mass manufacturers, such as Opel and German Ford.

Additionally, a new threat had appeared on the horizon in the national ‘Volkswagen’ program. The specifications of the new ‘Volkswagen’ car were still in development, but it was already apparent that the new, modern ‘People’s Car’ would make DKWs wooden bodied, two-stroke cars obsolete at a stroke.

In 1938 the Volkswagen was unveiled to the German public, and tens of thousands of Germans immediately signed up to the purchase scheme. Almost half a million would have signed up by the start of the war.

Although the Volkswagen and similar projects targeted the budget car market, the threat to Auto-Union was existential. DKW sales accounted for more than half of the group’s total sales and contributed more than two thirds of its profits. There was a lot of prestige in the luxury market, but little profit and a lot of expense. Both Audi and Horch, who had served this market, had been incorporated into the Auto-Union group in 1932 specifically because they were insolvent. Even within Auto-Union there wasn’t room for two luxury brands and Audi had virtually disappeared, producing small runs of vehicles every three or four years from a corner of the Horch plant. Auto-Union depended on DKWs cash flow to remain afloat.

Dr Hahn outlined a completely new program for the group which would involve the development of a single, modern Auto-Union range that would include a budget entry, mid-class entry and a luxury entry. To save cost, the new range would use modern production methods, share common components and have an unmistakable ‘Auto-Union’ style. Once established, the existing model range would be retired, and production facilities rationalized. The Auto-Union board endorsed the program.

To reduce production costs DKW attempted to develop a mass-produceable F series car in 1936. Designated the F6, the project had stalled in the face of the company’s difficulties manufacturing a self-supporting steel body. It was evident that cost saving through mass production and steel monocoque construction would be essential, but in Germany, Ambi-Budd held an exclusive patent over welded unibody construction. Negotiations with Ambi-Budd failed to reach a satisfactory resolution as the royalties sought by Ambi-Budd threatened to make the venture unprofitable.

Auto-Union engineers were in agreement that DKW’s two-cylinder 700cc two stroke workhorse engine had reached its developmental limits. As the new car would be constructed in steel, a larger, more powerful engine would be necessary. Since 1930 DKW engineers at Spandau had been working on the V4 engine for the ‘Big DKW’ range. This complex engine, which used charging pumps rather than crankcase compression, had proven to be extremely problematic. Although it generated more horsepower than the two-cylinder engine, it had a prodigious consumption of fuel and spark plugs, as well as being prone to catastrophic failure. Despite years of development and improvements, the engine remained unreliable, so an entirely new engine was required.

The cutting edge of DKW's two stroke engine development was the DKW motorcycle racing department. Numerous experimental engines were trialed, some with outstanding results. The pinnacle of DKW’s motorcycle racing engines was a transverse mounted twin cylinder engine with a centrally mounted charging pump. Unlike the problematic V4, the twin cylinder charging pump engine was capable of tremendous power output for its size. It was, however, a difficult beast and transforming it from a racing engine into a practical power-plant would take some time.

In 1934, the Scott Motorcycle company of England had unveiled a new three cylinder two stroke motor. The engine drew the immediate attention of DKW engineers and an agent was sent to purchase three Scott triples from a Belgian dealership in 1935, shortly before Scott went bankrupt. The bikes and their engines were shipped to Germany for testing. It would not be correct to say that the DKW three cylinder engine was copied from the Scott engine, but DKW engineers certainly used the Scott in their studies and by early 1938 a triple cylinder engine was available for research. In keeping with standard DKW practice, the engine was laid out transversely, with a wet clutch gearbox mounted on the right-hand side. Bench testing showed it generated 24 HP and ran very smooth. In December 1938, the engine plant at Zschopau was given approval to commence production of a pre-production run of 50 engines for road testing. All these engines received the suffix ‘V’ for versuch (research).

The first road test engine was mounted in pre-series F8 chassis number 7294. Some modification to the engine and gearbox mounts were required due to the engine’s greater width, but otherwise the vehicle was indistinguishable from a standard F8. The test vehicle’s first drive lasted only 50 metres before the gearbox gave out. The motorcycle style, multi-plate wet clutch could not handle the greater torque of the new engine and was shredded. A technical report indicates that six motors and gearboxes were shuffled through chassis 7294 in rapid succession - three engines; 429286-V, 429289-V and 429291-V, being cycled through in one six-week period! The placement of the transverse engine was regularly altered, sometimes with the axles and transmission to the front, as in the F8, and sometimes with the axles and transmission to the rear, as in the post-war F89P. A technical report from August 1939 reveals that the longest distance the gearbox was able to travel was only 500 kilometres. New and improved cast iron gearbox cases failed to improve things and gearbox problems would continue to plague the test vehicles right through the development phase.

The surviving transverse engine, number 429296-V, is on display at the Chemnitz Fahrzeugmuseum https://fahrzeugmuseum-chemnitz.de/

Fresh thinking was required. Dr Ferdinand Porsche and Prof. Eberan von Eberhorst had faced similar problems with the gearboxes of Auto-Union’s ‘Silver Arrow’ racers. Not only did the gearbox need to handle the immense torque of the Silver Arrow’s engine, it also needed to be short enough to fit within the cars’ limited wheelbase. Porsche achieved this with a compact gearbox unit that doubled back on itself. The design team adapted Porsche’s gearbox for use with the triple engine. This required the engine to be turned 90 degrees and the gearbox mounted longitudinally, doubling back on itself to place the axles immediately behind the engine. With the gearbox problem seemingly resolved (although issues would persist through the early 1950s in the IFA F9), the new unit was returned for trials in the F8 test car.

By 1939 the development of a longitudinal three-cylinder engine and its gearbox were completed, which allowed the factory in Zschopau to begin preparations for series manufacture at the end of the same year. At least 49 three-cylinder pre-production engines were manufactured, with numbers 429801-429900 reserved as test engines. The test department described production up to engine number 429810 as "old execution" while other documents mention three successive stages in the production of prototypes. Like their transverse counterparts, each three-cylinder longitudinal engine remained in their test chassis only a few thousand kilometres before replacement.

The new car introduced a number of other new features of DKW. The engine received a distributor ignition system mounted at the front of the engine, driven by a 90-degree bevel gear. Another was the introduction of a mechanical petrol pump. Earlier DKWs had the petrol tank mounted in the engine bay and used gravity feed, but new German road safety legislation required the tank to be moved to the trunk. Once road testing began however, it was discovered that vibration from the fuel pump progressively disrupted the ignition timing. Changing fuel pumps and modifying the ignition did not seem to help so, under time pressure, the engineers abandoned the distributor in favour of DKW’s tried and tested motorcycle technology of breakers and ignition coils. This simple and fool proof technology would remain as standard DKW practice until the DKW Munga was retired in 1970.

The mechanical fuel pump was also abandoned in favour of a vacuum pump driven by crankshaft pressure. It was a simple solution but would be an ongoing point of weakness.

One final problem would trouble the engine team – the exhaust. Two stroke engines depend on finely tuned exhaust backpressure for efficient combustion and fuel economy, but the exhaust flow of triple engine proved a challenge. Development was outsourced to the well-known and recognized exhaust specialist, Eberspächer. A transverse prototype engine was assigned to Eberspächer for testing, but they were never able to develop an exhaust that combined acceptable sound dampening without negatively influencing power, torque and fuel consumption. After Eberspächer’s failure, the design office decided to entrust the manufacture of the exhaust system to a brand that was until that time completely unknown, Bertram. Bertram would ultimately succeed where Eberspächer failed, and although no one at the time would realise it, this side show would in take on great significance in the future.

While engine development was following its own trajectory, Auto-Union's central body development department under Albert Locke, began styling the new “Auto-Union” form. Like other German companies, Auto-Union had dabbled in streamlined car projects from the early 1930s. Streamlining specialist Paul Jaray had bodied a Audi Front in 1933, and a rear engine DKW streamliner. Neither projects were deemed satisfactory. The opening of Germany’s first Autobahn in 1935 gave a practical incentive to the movement and Auto-Union began to experiment more seriously. Improved Audi and DKW Jaray streamliners were tested in 1935 and these trials demonstrated conclusively that vehicle bodies with low air resistance were capable of faster speeds and lower fuel consumption than standard body designs. These findings were supported by independent studies performed by the Kamm Institute and Konig-Fachsenfeld.

The 1938 rally and endurance racing season presented the company an opportunity to present a number of body designs for road testing. For the Rome to Liege endurance race, Auto-Union fielded a series of Wanderer W24s with streamlined aluminum cabriolet bodywork. Unfortunately, the Wanderers did not perform well in the race, but this was entirely due to their unsupercharged engines, which proved extremely unreliable. The team returned the following year with improved engines and performed better.

A more mature and practical design was applied to the 1938 Berlin Rome endurance race. A new aerodynamic body was designed by Albert Locke and manufactured in Spandau and fitted to pre-series F8 chassis  numbers 7301 to 7307. The cars were originally fitted with their original 700cc two-cylinder engines, but various test engines were swapped in and out regularly, including an 800cc V4 engine with charging pumps and pre-production transverse 3-cylinder engine.

In the body development department, stylist Gunther Mikwausch and modeler Wilhelm Bohm adapted these competition concepts for practical use. Sculpted models were tested in wind tunnels and the results assessed. They commissioned an expert opinion from the leading scientist in the field, Professor Wunibald Kamm. Kamm was able to share comparative figures of the ‘Volkswagen’ and the Adler Autobahn, and suggested some detailed changes to the body to reduce sensitivity to side winds.

By 1939, Dr Hahn’s vision of a modern ‘Auto-Union’ program had begun to crystallize. The first example was unveiled at the Berlin International Motor Show in March 1939. The Horch 930S was a far cry from the proposed DKW ‘Hohnklasse’ (high-class). The beautifully sculpted, streamlined body was cutting edge for the period. Fittings were luxurious. The most notable feature was a fold out basin for hot and cold running water that popped out behind the front wheel. The Horch 930S was not a mass production car however as the body was entirely hand crafted.

The Berlin exhibition car stunned motoring journalists and the motoring public alike.

The DKW Hohnklasse would not receive such an elaborate body, but its similarity to the Horch 930S was obvious. After mock-ups, a hand-built body was mounted on F8 chassis number 7350 with a transverse mounted engine numbered 429290-0 in 1939. Road trials demonstrated an impressive Cd factor of 0.42. The regular failure of the early gearboxes resulted in constant switches of engine and gearbox units. Longitudinal engine numbers 429804-V and 429817-V successively replaced the transverse engine.

Chassis 7350, with sunroof and two-tone paint scheme, was used in a promotional photo shoot for the new model, now designated the F9 in accordance with the DKW F nomenclature. A brochure was prepared for the 1940 production year but plans for series production were placed on hold by the start of hostilities in September 1939.

With all elements of the new car’s design were settled by the start of the war and Auto-Union had begun preparation for series production. The Zwickau engine plant was given the go ahead to manufacture another hundred engines. At least five vehicles were built and registered for the road by 30 September 1939. Apart from the original chassis 7350, the others were recorded in the archives as chassis 7294, 7344, 7347 and 7358, with chassis 7344 built as an open-topped limousine.

Dr Carl Hahn received one of these early cars and would clock up tens of thousands of kilometres, providing extensive reports on all aspects of the cars’ handling to the design team. Dr Hahn’s car constantly cycled back through the factory for improvements and repairs. One of the problem areas quickly identified by road testing was the inadequacy of the car’s brakes. The F9 was a much heavier car than the wooden bodied F8 and the F8’s cable brakes were not up to the task. Hydraulic brakes were installed as standard and, as these were sourced from the supplier who was gearing up for Volkswagen mass production, costs per brake unit actually decreased.

After Germany’s lightning victory over Poland in 1939, the expectation everywhere in Germany was that an accommodation would be reached with Britain and France and hostilities would come to end. Therefore, while Auto-Union and other auto companies were officially banned from developing new models, work progressed discretely behind the scenes. Several more pre-production prototypes were hand built in Chemnitz for expanded road testing.

By this stage, the early plans for monocoque, pressed steel construction were finally abandoned and a definitive decision was made use traditional body and chassis construction methods. Earlier, In 1938, Konrad Schulz and Dr. Rudolf Slaby from Auto-Union’s Spandau bodywork began discussions with independent vehicle designer, Friedrich Maier, in Berlin. Maier had been an aircraft engineer with Junkers before moving into vehicle design in 1934. He held a series of wide-ranging patents for things such as a height adjustable driver’s seat and, importantly, a manufacturing method for self-supporting steel car body. As a demonstration of his method, Maier built a single test vehicle, called the Maier Lightweight. This interesting vehicle was powered by a 600cc DKW two-stroke motor, mounted in the rear. It had a spacious interior, four doors, adjustable height seats and a single, centrally mounted headlight that turned with the steering wheel.


Nevertheless, Auto-Union management could not convince themselves that Maier’s small-scale operation would be able to meet their requirements for mass production. They were also fearful of any infringement of Ambi-Budd’s patents which would embroil them in costly litigation. The company postponed making any decisions on monocoque construction. In fact, it wouldn’t be until 1957 with the DKW Junior that Auto-Union finally adopted monocoque construction.

Panel bucks were manufactured at the body development facility and passed to the industrial tool company Allgaier to build the industrial presses necessary to commence series production.

The early plans for monocoque, pressed steel construction were finally abandoned and a definitive decision was made use traditional body and chassis construction methods. Panel bucks were manufactured at the body development facility and passed to the industrial tool company Allgaier to build the industrial presses necessary to commence series production.

Against domestic expectations, the military situation rapidly escalated with the German invasion of Denmark and Norway in April 1940. After a hard-fought German victory, an invasion of France and Low Countries followed in March. It took the Germans only six weeks to defeat the French army and push the British Expeditionary Force across the English Channel. In the short pause that followed peace feelers were put out to Britain and there was hope in Germany that the war would end. The British however, doggedly refused to negotiate and the path was opened for a long war. Government bans on new civilian vehicle production remained in force and would become progressively more restrictive as the war went on.

In 1941, the German government began to wind down military production and another round of discrete production began at Auto-Union. Although officially penalties for breaching the ban were severe, an internal report from 1943 suggest that at least 15 F9s were built during the second half of the war, including six other experimental chassis. All the F9s built to date had been improved through multiple iterations of improvements identified by extensive road testing, including the detailed reports and recommendations provided by Dr Hahn himself. Dr Hahn was to observe that in the DKW F9, Auto-Union finally had a car that could hold its own against all other auto makers.

As a sidenote, its important to understand how this fitted within Dr Hahn’s overall program. Having settled the body design with DKW’s budget offering, attention focused on Auto-Union’s mid-range car brand, Wanderer. Auto-Union had begun cross branding Wanderer products in the later 1930s. In 1936 Wanderer W24 sedan bodies were fitted with the unreliable DKW 4=8 engine and sold as the DKW ‘New’ Sonderklasse. The Sonderklasse received a different radiator grill and fittings were downgraded for the lower-mid range market, and despite the DKW’s inferior and troublesome engine, the new Sonderklasse still managed to outsell its Wanderer counterpart. Nevertheless, the Wanderer/Sonderklasse was always recognised as a stop gap until the new Auto-Union range hit the market in 1940.

Auto-Union’s new mid-range offering would be the Wanderer W31, which was basically the new Hohnklasse body fitted with a four-cylinder Wanderer engine. A mock-up was prepared, followed by at least one prototype for road testing.

A six-cylinder engine version was also considered as optional upgrade. Thus, by the end of 1941, the new Auto-Union program for the post-war period appeared to be clear. At the top of the range would be the luxurious Horch 930S. The mid-range would be serviced by the Wanderer W4 (with the 6 cylinder engine as an upgrade option), and the lower mid-range would be serviced by the DKW F9 Hohnklasse. The small engine 600cc F8 Reichklasse would remain in production as the sole budget priced competitor to the Volkswagen, until the Volkswagen reached full production levels. All other classes and models would be retired. The obvious streamlining and simplification of production would ensure Auto-Union would remain a viable automobile manufacture in a post-Volkswagen world.

But it was not to be. By 1944 Germany’s position was dire and all industrial resources were diverted to war production in a vain effort to stave off inevitable defeat. Despite this, at least one more F9 was built in early 1944 as the personal car for technical director William Werner. This car, the very last built, incorporated all of the improvements and modifications made to the pre-production series, but was fitted with a very early pre-production engine. The use of the earliest surviving longitudinal engine in the build is suggestive.

Werner did not get to enjoy much use of this car as it was badly damaged during a bombing raid over Berlin in late February the same year. The car was transported to Chemnitz in the spring of 1944 for repair and was probably the non-running car found there at the end of the war. As part of an attempt to evacuate Auto-Union technology, plans and tools out of the Soviet zone, the car was transferred to the Auto-Union branch in Hanover. In 1946 the British Ministry of supply seized the car as part of the Allied program to confiscate and evaluate German technology and shipped it to the School of Tank Technology in Cobham, Surry for evaluation. An article from July 1946 indicated that no detailed technical assessment was made although it was briefly mentioned in BIOS report 21. (‘The Motor Car Industry in Germany during the period 1939-1945’, pg. 21), which noted:
“the F9 car was developed solely to meet competition offered by the Volkswagen. The Volkswagen (subsidised) was cheaper than their F8 model and had more room and was faster. They reckoned that in producing the F9, which had a much better appearance than the Volkswagen and was about 15 kph faster, they would hold the market somewhere between the Volkswagen and higher priced cars.” (quoted from Karl Ludvigsen’s “Battle for the Beetle” page 373.

The car was repaired in England but dismissed after early testing and handed over to Australia for assessment. The war had convinced the Australian government that the country needed to develop an indigenous automobile industry and in 1944 proposed that Australia begin manufacturing “a car similar to the German low priced two-stroke DKW.” However, by the time the vehicle arrived in Australia a deal with General Motors had been agreed for domestic vehicle manufacture by GM Holden. Additionally, the complex legal web of patent ownership that was soon to play out between East and West German successor companies was sufficient to dissuade the Australian government of any plans to build an Australian DKW. In 1949 the car was sold by public auction of surplus military vehicles along with two 1946 Volkswagens that had also been shipped to Australia for evaluation. The car passed through various hands the car was purchased by Mr Leo Redfern of Victoria in the 1960s. Given the known fragility of the gearbox, and without any possibility of spare parts, it was inevitable that the engine would one day fail. This forced Mr Redfern to make significant changes to the car, transplanting the body onto a F89P chassis and engine. The original bonnet and radiator screen was replaced with that of the F89P.

The Werner car in the 1980s when owned by Peter Thorogood.

The car changed hands a couple of times before it was tracked down by DKW collector, Peter Thorogood in the 1980s. Peter also obtained the original chassis and engine (which was stored and dismantled in a box) and planned to do a full restoration. However, when the economy turned bad at the end of the 1980s, he was forced to put the car up for sale. By this stage Audi AG had become aware of the car and were keen to obtain this important vehicle for their collection. Forty odd years after it had left Germany the prototype finally returned home. Audi Tradition undertook the long awaited restoration. An early IFA F9 bonnet and grill replaced the missing original. The engine however was not fully repairable. The car is now on display at Audi's Ingolstadt museum where it can be enjoyed by everyone.

The Werner car has been exhibited at many auto shows.

The car gets a thorough inspection at an exhibition at the Chemnitz Fahrzeugmuseum in 2015.

The fate of the other cars:
Surviving photos of the cars allow some cross referencing of their registration numbers with their chassis numbers.

Chassis 7347 was originally registered as IA-230889 in Spandau before going to Chemnitz where it received the license number IV-73330.

As for 7350, despite the registration number IV-34564 appearing in the press photos, it was actually registered at the Audi factory in Zwickau as V-12126. The registration number IV-34564 appears on a number of different vehicles in a number of publicity shoots.

Chassis 7352 was owned by the Spandau testing department under registration number IA-228349. Chassis 7353 was registered in the district of Chemnitz as IV-4267.

Chassis 7358 was also registered in the same district as IV-4410.

This car, chassis 7358 would be presented to the Soviet Administration in Leipzig before being shipped to the USSR in 1946 under the number Proba 13-10. This very early car would be discovered in Estonia in 2016 and has since been shipped back to Germany for restoration.

We do not know which chassis were hidden under the registrations IA-34561, IV-5188, IV-0630 and IA-225868. The chassis number of the only 4-door prototype which, like 7350, seems to have been destroyed during fighting in Saupersdorf in April 1945, remains unclear.

By 1946 neither the new Auto-Union in the west nor its East German counterpart had an F9 in their possession and it seemed that all the pre-war development was lost. It would take a miracle for this particular phoenix to rise from the ashes. Surprisingly, the F9 would be ressurrected twice.

The ressurrection of Auto-Union: https://dkwautounionproject.blogspot.com/2020/05/collapse-and-reconstruction-history-of.html
The DKW F89P: https://dkwautounionproject.blogspot.com/2017/06/dkw-f89p-new-meisterklasse.html

This post incorporates detailed information from the historians Ralf Friese and Frieder Bach published in German. Frieder Bach's books are available here: https://fahrzeugmuseum-chemnitz.de/das-museum/publikationen/

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