Thursday, April 22, 2010

Das Kleine Wunder - the story of a remarkable engine

In 1906 a Danish engineer, Jorge S Rasmussen, founded a company in the little German mill town of Zchopau. In an old textile mill, the J Rasmussen and Co turned out machine parts and fittings for industrial steam engines. Jorge was a particularly driven and mercurial director. His interest struck out in many directions simultaneously. Wherever he saw an opportunity he snatched up businesses and by the 1918 he possessed an expansive array of companies.

Fuel shortages during the First World War had led Rasmussen to experiment with a steam powered car. This proved not to be a success and was abandoned by war’s end. In 1919 Rasmussen met engineer Hugo Rupp, who had been working on a small two-stroke motor. Rasmussen saw an opportunity and hired Rupp to develop the engine for commercial use. A 50cc demonstration engine was unveiled at an industrial show as a novelty engine nicknamed ‘the boy’s wish.’ Whilst a few toy engines were sold, it was quickly adapted for use as an auxiliary clip-on bicycle motor. The DKW ‘help motor’ sold extremely well in post-WW1 Germany, leading Rasmussen to begin building his own bicycles.

An DKW bicycle fitted with a DKW detachable engine.

The success of the bicycle engine led DKW to experiment with new designs. In 1921 DKW released the scooter-like Golem, powered by DKWs 140cc stationary engine mounted between the rider’s feet. It wasn't exactly a successful design but led in its turn to the improved Lomos in 1922, which featured larger wheels and the engine mounted beneath the rider’s seat. The Lomos sold a credible 2,500 units and turned DKWs attention towards building real motorcycles.

DKW's first real motorcycle was only a small step up from the motorised bicycles the company had been manufacturing to date. The stationary engine that had powered the Lomos was now mounted to the front frame of the bicycle with belt drive to the rear wheel. It wasn't a very efficient machine but it pointed the way to the future. Year on year the design was improved and sales steadily rose.

DKWs bicycle origins are clearly apparent in this 1922 machine. The 140cc engine was a real workhorse for DKW. It was sold in large numbers as a stationary engine but was also used in the Golem and the Lomos scooters, the first generation of DKW motorcycles, and the Framo and Phanomen tricycle delivery vehicles.

DKW’s engines of the 1920s had a good reputation but they suffered from a problem common to all two-strokes of the period of combustive efficiency and overheating. Two-stroke engineers everywhere experimented with changes to the port positions, domed, deflector pistons and split pistons in an effort to address this weakness. Hugo Rupp was an advocate of split pistons and would eventually leave DKW for Puch, where he would develop their lineage of split single ‘twingles.’ DKW experimented with domed pistons in their motorcycle range and went on to develop a V4 two-stroke with twin priming pistons for their large car range. The V4 proved to be an over-complicated failure that hamstrung sales of the ‘big’ DKWs.

Jorge Rasmussen was keen to find a solution as DKW had now begun building cars, which required bigger and more efficient engines. DKW’s first car, the P15 had used a water-cooled 600cc twin engine developed for the 1927 SB500 motorcycle. The engine was sufficient for the lightweight P15 but Rasmussen had grander ambitions for DKW. The next car was the ‘big’ DKW 1000 powered by the V4, specially developed as a car engine. Unfortunately, this engine failed to live up to expectations.

Meanwhile, in 1926 Doctor of Engineering, Adolf Schnuerle, had been experimenting with two-stroke engines. His solution of placing dual transfer ports on either side of the exhaust port effectively and effectively solved the two-stroke’s efficiency problems. Schnuerle was academic however, and did no more than patent his design and publish a paper. In 1927 Rasmussen stumbled across Schnuerle’s paper and instantly recognised its implications. Using Schnuerle’s ‘reverse loop scavenging’ removed the need for deflector pistons and complex porting in favour of simple, flat topped pistons. Rasmussen wasted no time and jumped on a plane and flew to meet Dr Schnuerle. This in itself was almost unprecedented as Deutsche Luft Hansa AG had only been founded one year previously. Rasmussen obtained from Schnuerle an exclusive license to use reverse loop scavenging in DKW’s engines. At a stroke DKW had made every other two-stroke engine in the world obsolete.

The new Schnuerle engine was introduced in 1928 and soon the company had become the biggest motorcycle manufacturer in the world, producing 65% of all motorcycles in built in Germany as well as supplying engines for many other German marques.

DKW soon expanded its motorcycle range to cater for every market niche, ranging from budget singles of 100cc capacity through to top of the range 600cc twins.

Part of the DKW motorcycle range in 1937.

The new Schnuerle engine was implemented into DKW’s new automobile range. The DKW Front series featured a 600 or 700cc two-stroke water cooled twin that put out between 18 and 25 horsepower (depending on size and spec). This engine would remain in production virtually unchanged until 1954.

The DKW range of two stroke cars in the 1930s.

In 1934 DKW introduced the RT100 motorcycle. Unlike other motorcycles in the lightweight class in Germany, the RT100 dispensed with pedals in favour of a proper kick start, had three gears and decent suspension. It was a lightweight, fast and stylish machine. DKW's advanced, production line construction techniques meant that DKW were able to pump out a record 60,000 units per annum. Despite its small size it was a robust and reliable design that influenced motorcycle design for years to come.

In 1939 the RT100 received an update and an entirely redesigned engine that gave it a significant improvement in power for a notional 25cc increase in capacity. The bike could hit 80kph and carry a passenger on the pillion seat.

The RT 125 - DKW's "little wonder" would become one of the most influential motorcycles in history.

The bikes nimble performance drew attention from other manufacturers around the world. With tensions rising in Europe and war imminent, the British Royal Enfield company attempted to get their hands on an example. They purchased three motorcycles through an agent in Holland and smuggled them back to England before war was declared. The bikes were examined and reverse engineered as the Royal Enfield Flying Flea. Due its light weigh the Flea was even used as a paratrooper bike during the war.

In Germany, the army had never showed any real interest in DKW due to their two-stroke engines, instead preferring the heavier 750cc BMW R21. Nevertheless, the RT125’s qualities as a light dispatch bike were obvious and military spec RT125 was built between 1940 and 1941, before being discontinued in favour of the larger DKW NZ350-1 as a dispatch rider's bike. The NZ350 saw service in all theatres.

An Afrika Korps NZ350-1 at the Audi Museum. Between 1939 and 1943 DKW simply produced its civilian NZ350 for the army without making any changes to design or build, but in 1943 lack of aluminum led them to produce the NZ350-1 with cast iron pistons.

Ironically, by 1943 the army was finding that the NZ350 was too heavy to operate as a light dispatch motorcycle and production of the RT125-1 was resumed. 12,000 RT125s were built for the Wehrmacht by the end of the war.

Post-war dismemberment...

Before the war’s end the Allies had agreed to annul all German technical patents and divide the German technologies between them. DKW's Zschopau factory wasn't damaged at all during the war but by fate found itself in the Soviet occupation zone. The Soviets stripped the factories of everything of value and shipped it back to the Soviet Union as war reparations. The Soviets shipped the NZ350 production line to Izkevsk and between 1946 and 1951 the Russians built 127,000 NZ350's under the IZH trademark.

The Minsk Moskva - the start of a long and venerable line of Soviet 125ccs.

The IZH 350 wasn't the only DKW knock-off the Soviets produced. They also began manufacturing a version of the RT 125 as the M-1A Moskva in a factory outside Moscow. In 1951 the plant was relocated to Minsk in Belarus. From then on Minsk specialised in 125cc motorcycles, exporting hundreds of thousands all across the socialist world. The collapse of communism and direct competition with cheap Japanese exports placed the company under extreme financial pressure however, and in 2005 the Belorussian government intervened to prevent the company going into receivership. Although its survival remains tenuous, Minsk continues to produce 125cc motorcycles today.

And meanwhile in England
In Britain, the designs for the RT125 were handed over to BSA, but initially no one knew what to do with them. Such a small engine just seemed to have no market in Britain where four strokes dominated. In 1948, BSA took a leap and developed the RT125 as the BSA Bantam in response to a potential export contract for India. The contract however fell through and so the Bantam was sold in Britain. To BSA’s surprise, the Bantam’s low cost and reliability made it an instant winner. The Bantam would go on to become one of the best-selling British motorcycles of all time, with a production run from 1948 to 1973 turning out almost half a million units.

For many in post-war Britain, the 'little rooster' was their first ride.

Across the Pond
In the US, Harley-Davidson had also received the designs for the RT 125 and in 1948 released their version as the Model 125. For Harley-Davidson, who specialized in big twin four strokes, this was their first foray into two stroke engines. In 1953, the engine size was increased to 165cc, but in 1955, they reverted back to the 125cc engine and renamed the bike the Hummer. It would continue in production until 1959.

Not quite the whole hog... and a two stroke to boot!

In 1960 Harley-Davidson used a 165cc DKW two-stroke in their scooter, the Harley-Davidson Topper. The engine was built by the Italian motorcycle manufacturer, Aeromacchi, whom H-D had partnered with to build the Topper. Ultimately it wasn't a successful venture.

Long regarded as a failure (it was), the Topper is now quite sought after due to its rarity.

And in the far east
Even in far away Japan the RT 125 was making its mark. In 1955 Yamaha reverse engineered an RT125 and releasing it as the YA-1. Exactly where they acquired their pattern is uncertain. It could have been from a German import, a Soviet version picked up in China, or even a copy of a Harley-Davidson Hummer acquired from US occupation forces. Regardless, the YA-1's design origins were clear. In later years Yamaha would copy the NZ35o and other German machines, like the Adler 250cc. Parallel twin two strokes following the DKW/Adler design would be copied by other Japanese manufacturers including Honda, Suzuki and Kawasaki and be produced in their millions right up to the present day.

Dejavu.... again.

And Resurrection.
After the loss of its Zschopau factory DKW re-established itself in Ingolstadt in West Germany and in 1949 began manufacturing the RT125W (W meaning West) from stocks of spares scattered around West Germany. By 1951 improvements to the design had been made, such as telescoping front suspension. Year on year DKW’s motorcycle range made its return with larger and larger machines re-entering the market. By 1955 even the RT350 twin was had returned, but sales waning.

In 1955 DKW attempted to break into the booming scooter market with the Hobby. Powered by a small 75cc engine, the enigmatic little scooter featured automatic, variable speed drive that gave it a surprisingly nimble performance. But the Hobby didn't sell as well as DKW hoped so they sold the manufacturing rights to the French scooter company Manuhurin which continued producing it into the early 60s.

I almost bought this gorgeous 1955 Hobby when I bought the Troll in 2008. It was very tempting but I decided that buying three scooters would just be a little too extravagant.

In 1957 DKW entered the moped market with the technically advanced 49cc Hummel. The Hummel was the first moped on the German market with a three speed gearbox. It sold well for a couple of years before sales slumped. Motorcycle sales were in terminal decline all across Europe as the post-war boom period was in high gear. Consumers wanted cars, not motorcycles. In 1958 Mercedes-Benz became majority shareholder in Auto-Union DKW and a condition of their investment was that DKW divest themselves of their loss-making motorcycle division. In 1960 DKW's motorcycle division was sold to Victoria, who merged with Express to form Zweirad-Union. ZU continued with the Hummel and various derivatives for a number of years.

The DKW Hummel was space age in its styling but never a big seller.

Mercedes-Benz would sell their share in Auto-Union to Volkswagen in 1964. Volkswagen wound up DKW and their two-stroke engine cars in 1966, reviving the Audi brand instead.

A life at half speed - East Germany
In East Germany, the Zschopau factory was resurrected by VEB, the state-owned auto conglomerate in 1948. In 1950 they began producing versions of the RT125 and NZ350 under the name IFA (Industrieverband Fahrzeugau AG).

An IFA and a MZ version of the RT 125cc at the East German Motorcycle Museum in Berlin.

IFA even resurrected DKW's racing heritage to compete in European championships.

In 1956, IFA was renamed Motorrad Zschopau, or MZ for short, and were soon producing a range of engines for their motorcycles varying in size between 125, 150, 175 and 250. MZ supplied the engines for the IWL range of scooters and Simson mopeds. In fact, VEB cancelled all four-stroke engine development for cars and motorcycles in favour of DKW’s cheaper and simpler two-stroke engine technology.

IWL's Pitty and Wiesel featured the DKW 125cc engine. Whilst it could push the little RT 125 along at a cracking pace, the engine really struggled to move these heavy beasts. In 1959 MZ increased the engine size to 143cc for the IWL Berlin and Troll. They were still under-powered though.

In 1962 the DKW 125cc engine, now more than 30 years old appeared in a new generation of MZ motorcycle - the ES125. The ES range led on to the distinctive styling of the MZ Trophy, East Germany's successful export motorcycle.

A group of early MZ ES and ETS models at the East German Motorcycle Museum.

MZ stuck with its two strokes until 1990 when it introduced the MZ 500-R four stroke. Unlike other Eastern European motor companies, MZ had built a strong export market for their motorcycles which enabled them to survive the transition from socialism to capitalism a little better than most. However, by 1993 MuZ (as it was then known) had pretty much lots its domestic market to Japanese imports and went into receivership. Its motorcycle production facilities were sold to the Turkish Kanuni motorcycle company, which still produces new bikes and spares for almost the entire range of MZ machines - which makes restoring an IWL or MZ bike far less taxing than it could be!

Here is a German video documentary about DKW and MZ.

The IFA brand name did not disappear with the name change to MZ in 1956. IFA took over the Audi production facilities at Zwickau and revived car production. Initially the factory build copies of the pre-war DKW F8 and F9 cars, both powered by water cooled two-stroke engines. In 1956 both pre-war models were replaced by a new car, the AWZ P70. At least it appeared to be a new car. It was in fact a prewar F8 chassis and running gear clothed in a modern style ponton body made of Duraplast. The P70 was a stop gap however and in 1958 was replaced by an entirely new car called the Trabant. The Trabant was powered by an 600cc air-cooled, two cylinder two-stroke engine based on a pre-war DKW design (it was developed by the Framo company for use in light trucks). 3 million Trabants would be built before production ceased in the mid- 1990s.

The infamous two stroke Trabant engine was the direct descendant of DKW's two-stroke motorcycle engine developed in the 1930s.

When it comes to longevity, there is little to compare with DKW's two-stroke engines. Their 125cc really was the first modern, reliable two stroke and its modern derivatives are still manufactured by Honda, Suzuki, Kawasaki and Minsk today - almost 80 years after they were first invented.


  1. Unfortunately the section relating to the DDR operations is confused and inaccurate (eg. MZ did not make engines for Simson, who were a completely seperate operation in a different area (Suhl, Thuringia)& there was no "organisation" called VEB (Volkseigener Betrieb - or "State owned enterprise), hence VEB Motorradwerk Zschopau, VEB Pentacon Dresden (cameras) VEB Filmfabrik Wolfen (camera film) VEB Automobile Werk Eisenach (Wartburg cars).
    IFA was the organisation that oversaw all vehicle production in the DDR, from bicycles to tractors.
    Kanuni has not produced MZ motorcycles for years & unfortunately neither has MuZ, which was closed by their bank some years ago & is the subject of ongoing legal processes as a result.

    1. You are right. The section on East Germany was written a long time ago when I could find little information in English. I've since realised some of it is quite wrong and I need to revise this. Thanks!

  2. Interesting read trying to find out who developed the berini