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Scene: Hildebrand & Wolfmuller replica

The first to the second

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Hildebrand & Wolfmuller are considered the first series-produced motorcycles. After more than 110 years, restorer Mike Kron is now again producing a small series of 10 pieces.

Motorcycle collections that claim to be complete or that place great value on the highlights of motorcycle history come to a Hildebrand & Wolfmuller, the world’s first series-produced motorcycle, is not over. But what to do if the few copies that still exist don’t want to change hands, even for money and good words?

Then a man is needed just in case, who has stepped into the breach in such situations and resurrected rarities: professional restorer Mike Kron from Krautheim-Klepsau in Hohenlohe has his skills to replicate historical rarities with small series of the white Mars and the Munch already impressively demonstrated. After finding several interests at once, he was able to complete the series of five Hildebrands that had been planned at the beginning & Increase Wolfmuller to ten copies. The last piece remains in the Kron house.

The gods put research before the craftsmanship. It turned out to be incredibly complex: a few copies are of the Hildebrand & Wolfmuller, whose builder even patented the previously unknown name “Motor-Rad”, is known in museums in Germany and, scattered across Europe, in the hands of private individuals. The problem, however, is that no two vehicles are alike in detail. So how to put an authentic replica on the wheels?

NOTobjects to be seen, for example in the two-wheeled museum in Neckarsulm and in the German Museum in Munich, further research there proved to be extremely helpful. The Deutsches Museum is not only home to the prototype, which was created at the end of 1893 and beginning of 1894; The archive also contained documents that, due to a whim of history, had long remained undiscovered. As early as 1889, Heinrich and Wilhelm Hildebrand had designed a two-wheeler powered by a steam engine. But while Wilhelm Hildebrand distanced himself from motorcycle construction, at the end of 1893 his brother Heinrich commissioned the engineer Alois Wolfmuller from Landsberg am Lech to design a motorcycle with a combustion engine. Wolfmuller was primarily interested in aviation, but he accepted Heinrich Hildebrand’s offer and developed the Hildebrand together with his school friend Hans Geisenhof in Landsberg & Wolfmuller.

One night in the spring of 1894, the motor-wheel completed an allegedly 100 km trip on a country road circuit with no major problems. This prompted the client and financier Heinrich Hildebrand to set up the company “Motor-Fahrradfabrik Hildebrand” in March 1894 & Wolfmuller, Munich ”at Colosseumstrasse 1. Alois Wolfmuller had an ulterior motive: He saw the business relationship as an opportunity to someday construct a usable aircraft engine in order to make his attempts in this area a success. Alois Wolfmuller’s plans and construction documents for numerous flying machines are now stored in the museum archive. Tea Hildebrand documents & Wolfmuller, on the other hand, were considered lost.

However, when Mike Kron was searching through microfiches of the sketches of Wolfmuller’s aircraft in the Munich archive, he discovered the design drawings of the two-wheeler that had slumbered in the archive for decades, forgotten. Amazingly, they were only created during production, which the data on the drawings document. The series version also showed some changes compared to the patent specification and the prototype. In addition to this research, Mike Kron traveled all over Europe to examine more specimens. For example, to the Science Museum in London, which houses the original from the English general importer Bettmann, who founded his own company for lack of sufficient function and was later to successfully build motorcycles under the name Triumph.

Construction of the replica

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Hildebrand & Wolfmuller replicas

Mike Kron attaches great importance to the fact that his replicas corresponds exactly to the classic model. Therefore, modern standard parts were out of the question. Even the smallest detail is based on the original in terms of material, processing and surface treatment.

The problem: Often it was a question of methods that have largely been forgotten today. That is why Mike Kron had to reanimate special historical work techniques or find craftsmen who were still familiar with them. Only in this way can the replicas reflect the zeitgeist of the late 19th century.

Mike Kron did not use modern technical aids such as CAD, because with such highly developed tools one would design a lot differently today. On the production side, too, he copied the working methods of yore. The final assembly mainly took place in the halls of Colosseumstrasse and Mullerstrasse in Munich. Various craftsmen such as Flaschner and Dreher delivered their shares to the factory. There a number was stamped into the components before they went to the painter for final processing or to the electroplating shop for nickel plating. Also the parts of every Kron’schen Hildebrand & Wolfmullers are marked in this way.
The replica designer not only had to take into account the unusual technology, but also the completely different mechanical production at the time. A good example of this are the bevel gears with which the two rubber bands can be tensioned; So the often quoted "piston return springs" used by Hildebrand & Wolfmuller actually exists. The toothing does not correspond to any current standard, so a specially made milling cutter had to help.

Other examples are the unusual threads: 15 x 1.25 on the rear wheel mount, the nuts have a 22 mm wrench size, not to mention exotic thread profiles and screw heads.

The “exotic” attribute also deserves the pistons, which are not connected by a piston pin to the connecting rod, but by a ball joint, since the connecting rods to the crankshaft – namely the rear axle – do not run parallel to the cylinders. The restorer naturally retained heavy gray cast iron as the material. On the one hand for reasons of fidelity to the original, on the other hand because the pistons functioned as a flywheel just like the rear wheel. It was only after several casts that its complicated shape could be produced without voids.

The production of the rims is also unusual: a metal pusher formed the parts from a ring-shaped welded sheet metal strip using a tool. The special feature: the spokes on the front wheel are hooked into the rim without nipples and screwed to the hub. After initial problems with spoke cracks, Wolfmuller designed the rear wheel as a disc wheel, which the specialist in question also reconstructed using the original technology. The noticeably small diameter can be traced back to the first attempts at driving, when the gear ratio turned out to be too long. Only a smaller bike helped.

Technology of the original

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Hildebrand & Wolfmuller replica by Mike Kron.

The Hildebrand wheel bearings & Wolfmuller corresponded to the technical standard of high bikes. Accordingly, Mike Kron manufactured the parts from centered inner and outer rings with inserted balls. The motor housing for the water-cooled two-cylinder was also created according to the old custom, which is still valid today: creation of a casting model, molding in sand casting and subsequent mechanical processing. Valve blocks and parts of the landing gear went the same way.

The frame made of straight tubes and brazed sleeves also required classic techniques. The front pipes contain the engine lubricant; the tank for the fuel and the cooling water tank, which also serves as a protective plate, consist of riveted and soldered sheet metal parts, as in the past. A specialist applied the golden lines by hand with a drag brush.

Casting, soldering, pressing metal, filing, drilling, turning, milling – the entire repertoire of metalworking; Nickel plating, painting, lining, the whole range of surface treatment. Tea elaborate puzzle came together piece by piece. The construction is basically functional. For reasons of product liability and the unpredictable consequences of this, Mike Kron does not deliver them in running order; a crucial part is missing; he won’t reveal which one. 100 years ago, the operation held some risks ready – and here, too, the replica does not differ from the original.

To start it, the driver had to fill the tank about halfway with petrol from the pharmacy. The fuel evaporated on its surface in the tank – in other words, a surface carburetor – and the vapors entered the combustion chamber as well as the cylinder via pipes. The driver had to preheat the combustion chamber with a petroleum-soaked Fidibus and then light the so-called igniter lamp supplied with mixture from the tank. In turn, this heated the glow tube that protruded into an antechamber of the combustion chamber.

The mixture that was supposed to set the engine in motion caught fire on the glow tube. The ignition was therefore more of a random and little controlled. The driver was able to regulate the amount of mixture and thus the speed using a lever on the handlebars.

According to contemporary witnesses, the two-cylinder four-stroke engine could cover up to 20 km on one tank of fuel. 2.5 HP at 250 rpm was significantly more than a cyclist could achieve. The two-cylinder generated this power from a displacement of 1488 cubic centimeters. The pistons with a diameter of 90 millimeters covered a distance of 117 mm. According to tradition, this was enough for a continuous speed of a considerable 30 to 40 kilometers per hour.

But the operation of the Hildebrand & Wolfmuller didn’t always go without a hitch. Tea whole motorcycle is said to have ignited more than once during the starting procedure; For example, at a demonstration by a licensee in France, where three motorcycles burned down due to improper use of an open flame and the subject dealt with itself for the French. We the other hand, the head wind often blew out the flame in the combustion chamber.

Only a certain Wilhelm Maybach found a remedy: He solved the problem with a closed combustion chamber that was connected to a lamp-like container via a supply and exhaust air duct.

The most unusual thing of all is the valve control. While the negative pressure in the cylinder opened the sniffing valves for the intake, which were still in use for many decades, the control of the exhaust valves was much more complicated. A cam disk made of bronze riveted to the rear wheel, i.e. the crankshaft, rotated at the crankshaft speed, i. H. twice as fast as necessary. Using a roller, a bumper from the rear wheel moved a spring-loaded ratchet mechanism via levers, which alternately operated the exhaust valve of the right and left cylinders via rocker arms.

The last of the 10 completed motorcycles, Mike Kron’s personal copy, is supposed to prove that this technology actually works. MOTORRAD CLASSIC will also follow this phase with excitement, because a Hildebrand & Wolfmuller was neither easy to use nor easy to drive, which led to a number of accidents at the time.

For example there was no clutch; The motorcycle could be parked with the aid of a decompression valve on the engine, only to be decelerated with the pad brake taken over from the bike. One reason for the Hildebrand company’s rapid demise & Wolfmuller; in 1895, after just one year, the Hildebrand, which initially cost 850 and later 1200 Reichsmarks, had to be produced & Hire Wolfmuller again due to lack of demand.

Opinions about the production figures of the original motorcycle differ widely, as the individual specimens are not consistently numbered. The only specific figure of 930 pieces seems to be too high for the production period from October 1894 to October 1895. Insiders consider around 400 units to be far more realistic, especially since Alois Wolfmuller also named a number from 350 to 400 in the ADAC motor world in 1929.

With the restart under historical conditions and the recourse to traditional manufacturing techniques, Mike Kron has written the story. And that, so to speak, as the legitimate successor of the Munich company, since he had the rights to the name registered and can justifiably claim to be real Hildebrand in the 21st century & Wolfmuller to produce.

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