Zweitakt Motorrad Museum
Zweitakt Motorrad Museum
...For Two-Stroke Lovers Only
RICHARD C. RENSTROM
ONE OF THE WORLD'S unique museums, housed in a quaint old sixteenth century castle, is located at Augustusburg, in East Germany, behind the "iron curtain." The area, called Erzgebirge, which means the ore mountains, is a beautiful setting with a deep green forest, alpine meadows and tall mountains.
The Museum is dedicated exclusively to the two-stroke motorcycle, thus the name of Zweitakt Motorrad Museum. Its portrayal of the invention and development of the two-stroke motorcycle is probably unique in that it is the only museum in the world devoted solely to the two-stroke.
The man who first thought up the idea for such a museum is lng. R. Hiller, a friendly gentleman who was a service representative for the famous MZ concern for many years, lng. Hiller began by restoring a lew old bikes tor himselt, but soon got the go-ahead trom MZ to start an official company museum. This was all the encouragement Hiller needed. Immediately, he began looking about for a suitable building to house his beloved old two-strokes.
The MZ company is located in Zschopau, in East Germany. Ihis also happens to be the home ot the pre-war DRW factory, one of the greatest names in the history of two-stroke motorcycles. Wanting to remain in the same general area, Hiller finally settled on the old castle at August usburg.
The castle itself was constructed in the classical Renaissance architecture so popular then. Originally, the castle was intended to be a hunting resort for a wealthy baron, but today it is used by the state as a tourist attraction. 1'he Zweitakt Museum occupies only a few rooms in the castle, but the total setting is extremely impressive and memorable. The rest of the castle is devoted to cultural and historical displays.
Hiller began setting up his museum in 1961 with the goal in mind of displaying a series of engines, machines, charts, graphs, photographs, and technical data that would show the viewer the total evolution and history ot the two-stroke motorcycle.
Today, Hiller has dozens of bikes from the very earliest antiques to the very latest works racers, and he has also acquired a library of historical and technical information that is unequaled. The result is impressive and totally professional.
If you were to visit this colorful museum, you would begin by viewing the world's first motorcycle, the invention of Germany’s Gottlieb Daimler. This contraption, built in 1885, featured a single-cylinder four-stroke engine that turned over at 600 rpm. lop speed was 7 mph. The frame and wheels were made of hickory wood, and a belt drive was used to transmit the power. The Zweitakt model is actually a replica of Daimler’s bike, the original being in the Daimler-Benz Museum in Stuttgart. Germany.
There were, of course, many important inventions leading up to Daimler s bike, such as a steam powered bicycle in 1817 and the first internal combustion engine by the French inventor, J. Lenoir, in 1860. 1 hen came the tourstroke design of Dr. N.A. Otto in 1876, followed by the two-stroke design ot England’s Sir Dugald Clerk in 1881. These early inventions are all depicted by wall charts, giving an orderly progression through the years.
Next is the world’s first motorcycle produced for sale the Hildebrand and Wolfmueller. This C.ertnan concern produced an opposed twin-cylinder watercooled four-stroke engine that displaced 1487ce. The con rods worked directly on the rear wheel. The engine was mounted centrally, and top speed was an astounding 28 mph. These primitive motorbikes were produced trom 1894 to l 897.
During these early years the twostroke engine was developed along with the four-stroke, with the British, Trench and Belgians leading the way. In 1912 and 19 13. Scott two-strokes won the Isle of Man I T. but thereafter side-valve engines became too fast and reliable tor the two-stroke to remain competitive. By the early 19 20s the ohv design with a hemispherical combustion chamber was showing terrific speed and exceptional reliability. Two-strokes slipped away to being used only lor “utility” lightweights.
The next significant step came in 1919 when the famous DKW concern was founded in Zschopau. This company dedicated itself to the development of the two-stroke, and tor the next 40 years they were to lead the way in showing the world the advantages ot t he t wo-st roke design.
Also on display is a beautitully restored 1919-1923 DKW motor-bicycle, which had a 122-cc engine mounted above the rear wheel. Power output was 1.5 blip, and a straight belt drive was used in conjunction with pedals to be used on hills and for starting.
The next display features several rare bikes, such as a 1921 (¡olein ((¡ermany) that must certainly be the world’s first motorscooter. There is a 1922 LomosSesselrad, a primitive belt driven rig that few have ever heard of. A slightly more modern looking bike is the 1921 Stock ((¡erman), which used an American 119-cc Evans engine that produced 1.5 bh|'> at 3200 rpm.
During the middle 1920s several improved two-strokes made their debut. These sported heavier frames, twoand even three-speed gearboxes, chain drives and more spirited performance. The 1925 DKW 200 displayed still used a belt drive, while the more modern looking 1927 Dunelt ( British ) featured chain drive and a “saddle” tuel tank that went over instead ot between the top trame tubes. All of these models are accompanied by large posters containing technical details and drawings.
In spite of these improvements, the two-stroke tell to the lowest ebb in its history during the late 19 20s and early 1930s. In grand prix racing the only model capable of gi\mg a respectable performance was the 250-cc 1’uch. which was water cooled and used a piston-type supercharger. In the roadster field the two-stroke was used mostly for inexpensive “utility” lightweights that rated very low on the popularity list.
The problems then were spark plugs folding and pistons freezing up. This was caused by the use of a raised deflector on the piston crown, employed in an effort to keep the incoming fuel charge from traveling straight out the exhaust port. The uneven shape ot the piston crown caused the piston to distort as it heated up. resulting in piston seizure. The only answer was to provide excessive piston clearance, which resulted in a loss ot crankcase pumping efficiency and a subsequent loss of performance. In addition, the poor engine breathing resulted in touted spark plugs. Two-strokes were delmitely an inferior proposition.
DKW had been battling this problem in their 175and 250-cc racing engines since 1925 with little success. 1 heir supercharged 250 churned out 15 blip at 4000 rpm then, but the blinding speed was invariably followed by piston seizure.
The man who solved this thorny problem was Dr. Schnurle. In 1934. he invented the now famous loop scavvnging design in which the piston crown was flat and two transfer ports were located neai the front of the cylinder and inclined upwards. The fuel charge thus traveled across the piston, up the back side of the cylinder wall, and Hum looped over the top of the combustion chamber and out the bottom exhaust port.
This new system had the advantages of the fresh fuel charge cooling the piston, a better piston shape tor less distortion, less loss ot fuel out the exhaust port, and less carbon deposit on the spark plug and ports. DKW thus found they could run a closer piston clearance, which in turn maintained the crankcase pumping efficiency. Reliability was greatly improved.
This loop scavenging principle is, without any doubt, the most important innovation in the history of the twostroke, and it put DKW into the racing business with a bang. They were fabulously successful and were responsible for improved roadster design.
During the 1430s DKW raced a 250 that won the European Championship in 1455, 37. 38, and 34. 1 hese German models were unique, featuring a splitsingle design in which two pistons mounted on articulated connecting rods worked on one combustion chamber. The transfer ports opened into one cylinder and the exhaust ports were in the other cylinder. Water cooling was used as was a reed valve. Output was 25 blip al 4400 rpm. The large compressor piston was horizontally mounted at the front ot the crankcase.
ln 1 436 the engine was modified to a piston type compressor and rotary inlet valve, which allowed crankcase charging to occur when it would do the most good. In 1434 the design was again changed to an eccentric vane blower, which raised the output to 40 bhp in the 250, and 5b blip in the 350. lop speeds were 111 and 122 mph respeclively, but the machines weighed 400 lb.
Ttii'n en nu» Wnrld War II and racine
was put aside. After the war, racing resumed, but a new HIM formula prohibited superchargers. DKW accepted the challenge and began designing new engines using a perfected loop scavenging method. By 1453 they had a fast 125-cc Single, and by 1455 their 350-cc Three was churning out 45 bhp at 4700 rpm good enough for a cool 140-mph top end when used with full streamlining.
Ihis DKW was rather unusual with its two vertical cylinders and one horizontal cylinder. The idea was to get a narrower engine than a transverse in-line Three. DKW dropped rotary valves and went back to piston-port control of the crankcase charging, due perhaps to the extra bulk required to house three rotary valves.
The following year the DKW works lost interest in racing. It was left to Walter Kaaden at the East German MZ factory to carry on the work. Kaaden can truly be called the “father ot contemporary two-stroke technology for putting the two-stroke in the winner's circle.
The first thing Kaaden did was to design a rotary disc inlet valve which allowed him to time the crankcase charging independently from the stroke of the engine. With a conventional piston-port engine the port opening and closing is symmetrical, opening the same number of degrees before top dead center as it closes past top dead center.
This, of course, is not the most desirable feature, since the crankcase vacuum is at its peak earlier in the stroke. By using a rotary inlet valve it is possible to time the inlet charge asym-
tage of the greater duration of crankcase depression to get the maximum fuel charge possible.
Kaaden found, for instance, that he could open the inlet port 154 degrees before TDC and close it at 58.5 degrees after TDC a duration of 212.5 degrees. About the best that can be had with a piston-port engine is lbO degrees, so a definite performance gain is available with the rotary valve. We might mention here that the only reason the inlet port can be held open on either engine after TDC is because the incoming charge of fuel has so much momentum that it will keep ramming in after the piston begins its downward travel and the crankcase compression is increasing.
1'he next Kaaden idea was the expansion box exhaust system that DKW had played around with on their 1 hree. 1 he idea is that the exhaust gas has great momentum as well as sound waves while traveling out the pipe. I his will cause a depression in the combustion chamber if properly harnessed, which in turn will help pull the incoming charge ot fuel from the crankcase. 1'his fuel charge has a tendency to travel right on out the exhaust port, though, so the pipe is designed to reflect a positive pressure wave back up the pipe late in the cycle which will pop the charge back into the combust ion chamber.
The third idea Kaaden pertected was the third transfer port in the skirt ot the piston. Originally it was thought that it helped lubricate the wrist pin bearing, but the extra port was found to provide a substantial boost in power as well as improve reliability. Since then additional ports have been added that have provided an even greater gain in power.
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Despite having been such a great pioneer in two-stroke design, Walter Kaaden has never been able to win a world championship. In 1958 the MZ 1 25 staggered the experts with its flatout speed, but Ernst Degner w'as not quite able to defeat Carlo Ubbiali and his MV Agusta. In 1959 the MZ 250 Twin made an impressive showing, and since then the hast German bikes have been in and out of contention from year to year.
Walter’s failure to capture that elusive world championship has probably been due to the limited budget under which he has been forced to operate, since MZ isa rather small company with lilt le capital to mount a massive racing campaign. As a result. Walter has witnessed the Japanese firms use his ideas to win countless world titles, only proving that it still takes money to develop a brilliant design into a winner.
As a fitting tribute to Kaaden, the Zweitakt Motorrad Museum has many examples of his work sleek racers as well as the ESDI-proven production models.
Today, if you are fortunate enough to obtain a visa to travel behind the iron curtain, a tour through this museum will reveal the very first motorcycle in the world, and then the first of the twostrokes. There will even be some surprises. such as the 1930 G TP Veloeette a 250-cc Single with an oil tank and positive oiling to the crankshaft 35 years before the Japanese thought they had “discovered" a new ideal And then there is the early DKW with Schnurle’s loop scavenging, plus all of Kaaden’s ideas in pictures and steel before your eyes.
Perhaps the finest display, and one that most perfectly represents the spirit of this museum, is the display of the 1939 DKW grand prix machines. Before you are the actual machines in concourse condition and their description in drawings and pictures.
Several posters show the immortal riders Ewald Kluge and Sigfried Wunsche. The DKWs are in full flight the rear tire smoking and the loudest exhausts ever to grace a classical course are screaming their defiance for all to hear. The supercharger is gasping for more air to feed that rotary valve, and the rider is poised over the foot pegs as the water-cooled beast takes to the air over a jump in the cobblestone road. In a flash he is gone and you are again standing before a silent display thinking about all that has gone before.
