Adler model 2 a special motorcycle

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Adler model 2 a special motorcycle
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A dream for hobbyists: Adler model 2

Looks like a bike, but runs with an Adler single cylinder

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If gifted craftsmen have an engine, they don’t have to worry too much about everything. They build it themselves: Dietmar Berg accidentally got hold of a naked Adler single-cylinder from 1903 and recreated the motorcycle that went with it. Little by little, in just under four years.

A comfortable study inspires thoughts, everyone who has to write, plan, calculate knows that. To make his office even more cozy, Dietmar Berg put a pretty single cylinder on the shelf six years ago. Inlet sniffer valve and bottom-controlled outlet identified it as an early work of motorization. Fits, said the passionate motorcyclist and was therefore inspired from now on.

In terms of driving, he feels obliged to modernity and regularly drives a BMW R 1100 GS or Ducati 750 Supersport, and occasionally a self-restored 350 MV or 125 Morini. But his joy in complicated sheet metal work always takes him back to the first decades of the last century. In his free time, the 51-year-old builds tanks for motorcycles, and in 2005 he exchanged the said motor for two of them.

A.dler is written on the crankcase, and of course the master electrician quickly found out that it was the very first engine of the Frankfurt company’s own. It came out big with bicycles. When this market flagged shortly before the turn of the century, typewriters, cars and motorized tricycles were also produced on the Main. The first motorcycle followed in 1901, powered by a De Dion single-cylinder. Two years later, the then popular French built-in engine was replaced by the same two-horsepower design that adorned Dietmar Berg’s study.

The Internet spat out three or four pictures that showed the motorcycle and its engine in its original state. Adler Model 2 – built for only one year because the rapidly growing market required constant technical innovations and rapid model changes. Not infrequently, but very rarely, such a part had to be meanwhile, and somewhere close to this statement Dietmar Berg’s inspirations got out of hand. Instead of correspondence or tax returns, when looking at his engine it occurred to him more and more often to build a motorcycle around this single cylinder. The Adler Model 2, as true to the original as possible.

The parts search confirmed Berg’s assumption that he was interested in an extremely rare motorcycle: no carburetor, no wheels, no exhaust – nothing, after months of research. He was still looking at the bare engine, but now the idea had become a challenge. Berg wanted his Model 2, so he would have to build more new things than originally planned. Namely everything.

To warm up, the frame and tank were first created in the well-stocked hobby workshop (see box on the right). Familiar terrain for Berg, who had also reproduced the load-bearing parts of a motorbike. He also took care of the engine. At top dead center it measured a clearance of almost 0.25 millimeters between the piston and cylinder – far too much even for a pair from the pioneering days. So he had a piston made. An engine overhaul bored and honed the cylinder and coated the new piston to minimize friction. Berg was able to replace the malade exhaust valve with an auto part by slightly reducing its plate diameter. Then he made a new valve guide out of gray cast iron and ground in the valve. The radial play on the gunmetal plain bearing bushes of the full-flanged crankshaft was negligible, only the axial play was optimized with appropriate spacers.

The astonishingly good condition of this single cylinder is a clear indication of Adler’s outstanding position in the automotive industry at the time. Company founder Heinrich Kleyer was a missionary bicycle friend. But he was also a passionate entrepreneur and recognized early on that his rapidly growing company needed several pillars. His auto engineers developed special talent: before the First World War, Adler advanced to become one of the leading brands in Germany; in 1914, every fifth car sold in Germany came from the imposing Frankfurt factory.

Adler vehicles aroused the public’s interest with remarkable regularity, which is why the suspicion is that PR was already being used in Frankfurt when it didn’t even exist. As early as 1902, the poet Otto Julius Bierbaum had explored Italy in an Adler automobile; his report is considered the first German-language car travel book. The German nobility flew on eagles and were constantly photographed with the bodies from the Main metropolis.


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Adler model 2.

But Adler motorcycles also gained some fame: To thank the Prussian Prince Heinrich for his membership in the German Motorcyclists Association, the latter organized a relay trip from Stuttgart to Kiel in 1904. Such competitions answered the most pressing question from the general public – “Will these new vehicles hold up?” – and were accordingly popular. Two Adler pilots successfully responded and presented the prince with their association’s letter of thanks after a 20-hour drive at an average speed of 53.5 km / h. Whereupon Your Royal Highness took up pen, praised the outstanding qualities of an Adler motor two-wheeler model 3 that she had tested and bought the same.

However, the prince did not feel the need to moderate the rules of motor vehicle tax that came into force in 1907, according to which motorcycling in Germany became almost unaffordable. And Heinrich Kleyer did not feel obliged to build more motorcycles – he could also be a very sober entrepreneur and stopped building motorcycles in the same year.

Back to the predecessor of the royal vehicle. Model 2 had battery coil ignition, and magnetos only became standard a little later. Prince Heinrich should have had one, but Dietmar Berg didn’t want one. A chain sprocket on the right stump of the crankshaft proved that its engine – like many others at that time – had been converted to an external horseshoe magnet. In the interest of the desired original condition, however, Berg milled a new base plate and ground an ignition cam that moves a modern interrupter. In the middle of the tank is a Bosch high-performance ignition coil and a powerful battery. This should allow more than the 2,000 to 3,000 kilometers promised in 1903 per battery charge.

Berg devoted himself to all the details that make such an old motorcycle seem so wondrous today. The pull and push rods for the brakes and engine control took some time. In the end, everything should be aligned nicely in parallel without the rods and levers colliding with the tank or motor. The handlebar offset had to be exactly the same as the original. So Berg filled a seamless steel pipe with an outer diameter of 25 millimeters, heated it and bent the desired radii. Then the handlebars were hard-soldered with the connection to the head tube, finally – like all bare parts – sanded and polished for hours, as with the original in a specialist shop, copper-plated and finally nickel-plated.

In the meantime, the recreational restorer had broadened his view of the Internet and found two contemporary bicycle hubs. One of them was intended for the rear, but was suitable for the front because it has a matching external thread to accommodate the drum of the characteristic external band brake. Of course, they weren’t available online, so Berg sat down at his computer and designed. From the solid he turned the basic shape and then clamped it on the rotary table of his milling machine. He milled six uniform recesses by transferring the respective coordinates from the PC drawing to the infeed of the rotary and milling table. The three graceful levers with ratchet mechanism for valve lifter, ignition adjustment and intake rotary valve as well as the lamp holder with the Adler logo and the ingeniously designed belt tensioner were created in the same way.

The final spurt was approaching, an exhaust was needed. Berg had long been in contact with the owner of a Model 2 through the Adler Club, but his machine does not have an original exhaust. The striking piece consists of many deep-drawn and then welded individual parts. Berg calculated the length on the basis of some original measurements that his friendly colleague had given him. These were then compared on photos with the part to be manufactured. He also did the same with the special accessories: In an Adler catalog from 1906 he discovered a clever stand that functions as a luggage rack when folded up. He wanted it, built it out of stainless steel – and polished again for hours.


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Leverage: in front the belt tensioner, behind the valve lifter, behind it the mixture throttle and ignition adjuster.

Now the paint was still missing. Berg experimented with contemporary paint, but decided for practical reasons for modern acrylic paint from the spray can. He deliberately refused to give his sweetheart a high-gloss finish because, in his opinion, it didn’t go with this era of vehicles. Then he changed his trade because he wanted to build the pretty saddlebag himself. Made of thick leather and, of course, with the Adler lettering, for which he specially made a press die.

About 500 of the total of 700 planning and handicraft hours are described here. Admittedly, this is insufficient, but a novel was required to portray Dietmar Berg’s obsession with craftsmanship. Incidentally, that would also have two tragic chapters. One about how he failed to build a belt rim and had to hire a Dutch specialist. One thing about the engine not wanting to run. Everything was ready, a historic Adler bicycle saddle was quickly mounted and the candle lamp was attached, then the motorized early days should rise. But that consisted entirely of misfires, until Berg removed the side cover of the engine and found that the markings on the steering wheels were wrong. Botchy in the Adler factory?

It doesn’t matter, now Model 2 is chugging, and a mission has been fulfilled: In Dietmar Berg’s opinion, far too many engines in museums are falling silent. His is saved.

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