Imme R100 - Purity of Design

Image Source

There are rare moments of remarkable clarity and forethought in the realm of motorcycle design, when machines are produced with such innovation and beauty that they are scarcely credible as products of their time. These motorcycles can occupy one of two positions in subsequent conception: they can be held aloft as gamechangers, as the designs that pushed the goalpost forward and forced everyone else to catch up, or they can fade into obscurity only to be appreciated by a limited few who recognize how advanced they truly were. Many remarkable designs fall into the latter category, the genius of their creators only recognized long after they pass into anonymity once the rest of the industry has caught up to the future that was laid out well in advance. Appreciation of these machines is only possible in hindsight when we see how their details foreshadowed subsequent trends.

German motorcycle designer Norbert Riedel was one such forgotten innovator, and his Imme R100 proved to be a masterpiece of design that has only began to earn true appreciation in recent decades. Once a cheap and cheerful form of transportation that was designed and built within the restrictions of a postwar economy, the Imme became one of the most fascinating examples of motorcycle design to emerge during the mid-20th century – and would prove to be one of the most beautiful motorcycles of any era. They were a machine out of time, a vehicle that applied nascent principles that were still decades away from the mainstream, and a series of ingenious design elements unified into a coherent whole that has since earned the accolades of some of the world’s motorcycle elite. The Imme was not just a cleverly constructed motorcycle, it was one of the most beautiful pieces of modern industrial design that nobody has ever heard of.

Image Source

Norbert Riedel was born in 1912 in Jägerndorf, then a part of Austrian Silesia, to German-speaking parents who were among the significant majority in the region. Following the close of the First World War the city was ceded to the newly established Czechoslovakian state, under whose administration the region remained until it was claimed by Germany during the annexation of the Sudetenland in 1938. Riedel began a career in engineering which saw him join Ardie in 1935, where he cut his teeth working on various two-stroke designs produced by the Nuremburg company, eventually rising to the post of lead engineer. Powered by bought-in engines produced by various firms, mainly two-stroke, with some four-stroke models including some JAP powered singles and twins produced in the 1920s, Ardies were well respected and competitive designs during the interwar period. Riedel’s exact contributions to the company are vague (much like many details of this story), a fact compounded by the significant bombing the Ardie factory suffered during the Second World War that led to the destruction of most of the company records.

Image Source

What is clear is that in subsequent years Riedel would make a small but interesting contribution to the German war effort. Development of the modern jet engine began in Germany during the interwar period and eventually culminated in the production of the BMW 003 and Junkers Jumo 004 turbojet designs which would power the Heinkel He 162 and Messerschmitt Me 262, respectively. These early jet engines were fickle devices that taxed the metallurgy and engineering of the day, and required auxiliary engines to be fitted for the complicated multi-step start up procedure. At some point in the late 1930s or early 1940s Riedel, now working for Victoria-Werke in Nuremburg, designed a two-stroke, horizontally-opposed air-cooled twin which would serve as the starter for these production turbojets. This compact 270cc engine, named the Riedel Anlassermotor (starter motor), featured a remarkably oversquare design with a 70mm bore and 35mm stroke and produced 10hp at 6000rpm, with power transferred from the crankshaft through a series of planetary gears to a stepped gear which meshed with the central shaft of the turbine.

Image Source

This oversquare configuration was odd for a two-stroke, where longer strokes are favoured to provide more port area and longer timing, as the ports are cut into the cylinder wall. Common practice in two stroke design is the use of square (equal) bore/stroke ratios, or undersquare configurations with a stroke that is longer than the bore is wide. Short stroke engines are common today in four-stroke machines because in a four stroke cylinder port area is relative to the size of the bore, with a bigger bore allowing larger valves and bigger holes for the mixture/exhaust to flow through (and reduced piston speed via that shorter stroke, which means improved ability to safely rev higher and exploit the improved breathing characteristics of the large ports). The short stroke configuration of Riedel’s engine gave the device extremely compact dimensions, a feature borne of the necessity to allow it to fit within a cone-shaped nacelle fitted in the nose of the turbine while leaving space for a 3 litre fuel tank.

Image Source

Regardless of the peculiarities of the design, Riedel’s Anlassermotor proved to be a reliable and effective design that earned Victoria a contract for series production of the engine, beating out competing designs from BMW and Hirth. While all the initial designs were rejected by the Reichsluftfahrtministerium (RLM), Riedel/Victoria’s engine was approved and given a production contract following a second round of trials. Officially designated the RBA/S10, RLM design number 9-7034A, the engine could be started externally via pull cord (visible at the tip of the nose cone of the engine) or with an integrated 24 volt electric motor activated from the cockpit, accomplished in the Me 262 by a plunger on the pilot’s right hand side. The raspy, unmuffled unit would be fired and run to spin the turbine up to 800 rpm, at which point the pilot would activate the injection of the fuel/oil starting mixture and ignition systems on the main engine. Once the turbine hit 1800 rpm the starter motor would be shut off and the remainder of the starting procedure would be controlled by the pilot. The Anlassermotor would only be required to run for about one minute – a good thing considering the air-cooled engine was completely shrouded and would likely overheat if run for much longer, though an integrated fan was fitted at the forward end of the engine to improve cooling within the confines of the tiny nacelle.      

Image Source

Following the end of the war Riedel found himself a free agent with the benefit of some positive notoriety among the Allied victors due to his contribution to the Nazi jet program, which had been intensely scrutinized and reverse-engineered by the Allies during and after the war. Legend has it that it was the Allied appreciation of Riedel’s starter motors that earned him some favouritism that would enable him to establish his independent motorcycle manufacturing operation not long after the war, though concrete details outside of apocryphal statements are scarce. In peacetime Riedel Anlassermotoren found their way into other civilian projects, and some examples survive with sprockets attached to their output shafts to drive a chain in a homebrewed go kart. Ingenuity in the postwar period, fed by a steady supply of cheap military surplus, was often limitless in its potential despite the austerity present in a continent ravaged by a violent war, a reality that would inform many of the design ideas Riedel would adopt in his later work. Considering their particular application (and the limited number of jet turbines produced by the Nazis during the war), and the attrition rate you'd expect for surplus items from a losing nation, a surprising number of Anlassermotoren have survived into the present with a few caring enthusiasts restoring them to running order. You can even purchase an example right here for under 1000€.

Image Source

Victoria-Werke suffered significant bomb damage during the war and would not resume motorcycle production until 1946, making them one of the fortunate companies that managed to survive the conflict (and their association with the Nazi war machine) to resume civilian production. By this time Riedel was already formulating ideas for a complete motorcycle of his own design, and in 1947 he would set out on his own to develop his proprietary machine.

Image Source

In April 1947 the first contract documents were filed in the founding of Riedel Motoren GmbH, marking the genesis of Riedel’s motorcycle company as a private legal entity. Work on the prototype machines began in Muggendorf in 1947, with the first chassis hitting the road in December, but with facility space limited and production aims ambitious an expanded Riedel factory would need to be established in a new location. In June 1948 Riedel Motoren AG would be established in the Bavarian Alpine town of Immenstadt, encouraged by the support of the local government which wished to provide employment to the area’s skilled workers, who had previously been employed in the now defunct aero industry.

Image Source

Postwar Germany was, like most of continental Europe, going through the agonizing process of rebuilding their society after a disastrous conflict that left their industries in literal ruins, their economy in shambles, and their people starving and scarred by years of conflict. It was a time of austerity and small steps towards recovery, and in the years following the end of the war simple, inexpensive transportation was in high demand. This was the era when small, cheap motorcycles flourished as an economical alternative to cars, providing the modest beginnings for many nascent motorcycle brands across Europe. The existing companies that had survived into peacetime retooled their factories to produce goods that suited the new economic reality of Europe.

Image Source

Norbert Riedel had the foresight to recognize the growing demand for cheap and cheerful transport, and put his skills as an engineer to good use by designing a remarkably well-thought out machine that was as innovative as it was inexpensive to build. It was a masterpiece of good design. And it was beautiful.
His creation was dubbed the Imme R100, a colloquial German term for “bee”, and given a cheery mascot in the form of a stylized bee with windswept wings riding a motorcycle. The origin of the Imme name has been debated. While it would be obvious to see the name as an abbreviation of the factory’s home in Immenstadt, it has been noted that the name and bee logo had already been determined while Riedel Motoren was still based in Muggendorf. Some sources suggest that the name was provided by the workers who noted the little motorcycle sounded like a buzzing bee. Curiously an attempt was made to market the R100 in Belgium as the “Golbi”, but aside from exhibiting a Golbi-branded R100 at the 1949 Brussels Motor Show no evidence of a rebadged Imme survives.

Image Source

Whatever the case of the nomenclature of the company’s product, The Imme was a remarkably advanced machine that offered budget-conscious buyers an exceptionally handsome and cleverly designed motorcycle for their money when production began in mid-1948. The base model cost 775 DM, and that netted you a 99cc, 52x47mm, Schnürle-ported two-stroke single producing a healthy 4.4hp at 5800rpm with a 7:1 compression ratio – a modest figure by modern standards, but nearly double what the contemporary competition was squeezing out of their 100cc engines.

Image Source

The engine was stylized and streamlined, with an oval-shaped profile to the horizontal cylinder, the tiny Bing carburettor hidden behind a polished cover on the right hand side while the magneto resided under a cover on the left. The cylinder head and barrel were cast as one piece to simplify production. The unit gearbox was a simple three-speed unit that lacked a neutral position, saving some complexity but forcing the rider to keep the clutch disengaged at a stop or on startup, aided by a simple wire loop that could be flipped between the lever and perch to lock the lever in position. Riedel developed a linear-shifter “draw key” transmission to further simplify construction. Rather than having a shift drum operating forks within the gearbox, the main gears were hollowed out with detent balls set within their hubs. A shaft with wedges machined into it sat within the hollowed-out countershaft. When the shaft was moved in and out, the wedges spread the detent balls outward to mesh with notches cut into the hub of the gears, locking the gear and engaging the desired speed of the transmission. A twistgrip on the left bar connected to the gearbox via a cable linkage which pushed and pulled the draw key. First gear was in the central position, twisting down selected second while twisting up engaged the direct-drive third.

Image Source

The throttle was controlled as you would expect via the right hand grip, but doubled as the kill switch – pushing the grip all the way forward shut off the engine. One of the most interesting features of the engine was the asymmetrical crankshaft, which featured a single-sided crankpin mount and one counterweight. The big-end bearing was secured to the crankpin with a circlip and the whole bottom end was supported by a single main bearing on the left side – a clever bit of cost saving, but one that would ultimately prove to be the fatal flaw of the design.

Image Source

To keep manufacturing simple and material use minimal the frame, front fork leg and rear swingarm used the same diameter steel tubing. The engine was rigidly mounted to the swingarm – thus the power unit was suspended along with the rear suspension and moved in unison with the rear wheel, much like a modern scooter powerplant. An Imme on the move was a curious sight, with the engine bobbing up and down in harmony with the rear suspension.

Image Source

One of the most forward-thinking elements of the chassis was the suspension arrangement. Both front and rear wheels were suspended on single-sided arms, a single-sided girder fork on the front and a monoshock swingarm on the rear. This rather modern arrangement was a product of the material shortages in postwar Germany – the single sided design meant that half as much steel was needed to manufacture the front and rear arms. The front suspension is reminiscent of the unusual suspension fitted to the Gilera CX, which used a single-sided arm connected to a single telescopic fork leg – 40 years after the Imme was introduced. The rear swing arm doubles as the exhaust pipe, a unique element that would not be recreated until Confederate designer JT Nesbitt used the idea in his second generation Hellcat introduced in 2003, more than 50 years after the Imme hit the streets. The rear suspension uses a horizontal monoshock in a straight-rate configuration bolted to pressed steel mounts attached to the frame and fender, triangulated through the reinforced fender mount that supported the left side of the rear axle - a good 30 years before cantilevered monoshock rear suspensions came into vogue (if we conveniently forget the contemporary H.R.D Vincent chassis, anyway). Rudimentary adjustable friction dampers at both ends kept things under control. The front and rear wheels were interchangeable, and an optional spare wheel could be mounted beside the rear wheel on the mudguard support bracket.

Image Source

The whole package was clothed in simple, elemental bodywork that left the fascinating chassis and engine unhindered by flashy baubles or useless styling exercises. You had mudguards, a fuel tank, a headlamp nacelle, and sprung saddles for the rider and passenger (if so equipped). The curved backbone of the frame and the shapely engine took centre stage. It was simple and beautiful, a product of the limited means that determined many of the design elements - without looking like a cut-rate budget machine, despite its modest sticker price. The first examples were available in one colour only, a deep oxide red with the only ornamentation being that cartoonish riding bee taking pride of place upon the tank.    

Image Source

In 1948, the first year of production, a mere 80 machines were assembled. By 1949 the Immenstadt factory had 370 employees producing up to 500 Immes per month, for a total of 5000 examples by the end of the year. Margins were slim on the relatively inexpensive R100, and Riedel hoped to make up for the meagre profits with significant volume. Small changes were made throughout the production run, some to simplify production even further, such as a combination headlamp-rectifier which converted the alternating current of the magneto to direct current through the filament of the headlight bulb. Solutions like this would come to define the ingenious ideas behind the Imme, where simplicity was key and the often-referenced-but-rarely-executed engineering ideal of multiple uses for a single component was evident throughout the design. It is this purity of form and function, the result of the thoughtful consideration of practical details, that have earned the Imme a degree of appreciation that is completely disproportionate to its obscurity. The Imme was remarkable because compromises didn’t hinder the design – it was those very compromises that made it brilliant.

Image Source

In January 1950 a more upmarket “Export” version of the R100 was introduced, retailing for 850 DM. This upgraded Imme was available in green or black in addition to red, with hand-painted pinstriping to distinguish it from the base “Standard” model. For your extra 175 marks you received decadent luxuries such as a battery, a horn, a speedometer, a centrestand, an improved seat, and some chrome trim pieces. In May a “Luxus” model was introduced for 865 DM, adding some more chrome trim to the horn cover, rims and hubs in addition to the options present on the Export. The popularity of the Imme was such that 1000 machines were now being produced per month, with over 10,000 sold before the end of 1950. R100 powerplants were also sold to the Fritz Fend company to power their third generation of Flitzer three-wheeled microcar, a single-seat machine marketed as an “invalid carriage” - an unfortunate reality in a nation with an overwhelming number of citizens wounded and maimed during wartime.

Image Source

Aside from being beautiful and inexpensive, and backed by a successful marketing campaign, the R100 offered good performance and an extremely compliant long-travel suspension which was an asset in various forms of small-bore competition. Top speed was claimed to be better than 50 miles per hour, while netting up to 150 miles to the gallon. Immes successfully competed in European events on and off road across the continent and earned a reputation as reliable and sprightly little machines. Riedel was also notable for offering a manufacturer’s payment plan on the Imme  – with a minimum downpayment of 250 DM you could finance the balance of the purchase price for up to 12 months, which worked out to 50 DM a month for a Standard, 75 DM for an Export, and 90 DM for a Luxus. Everything added up to the Imme being a winner, a machine that should have propelled Riedel into the history books – but trouble was on the horizon.

Image Source

Work began on an enlarged R100 named the R150 and advertised as the Neukonstruktion Imme. This new design retained many of the characteristics of the R100 with the extra power of a parallel-twin cylinder engine; the chassis was unchanged aside from the fitment of slightly wider 2.75x19 inch tires, and prototypes were pictured in what appeared to be R100 Luxus specification, with only the position of the carburettor and the presence of twin spark plug leads giving away the new zweizylinder engine. The engine was heavily reworked but was still clearly an evolution of the R100 architecture. As on the R100 the cylinder and heads were cast as a single component, with the intake and exhaust runners placed between the two cylinders in a downdraught configuration, with the single carburettor placed above the engine. Bore was 48mm and stroke 41mm, with 6 claimed horsepower at 5000 rpm. A conventional four-counterweight crankshaft supported by two main bearings was used instead of the single-sided setup of the R100. Gear ratios were revised compared to the R100 but the gearbox was still a three-speed draw-key design shifted by twistgrip, and it was still devoid of neutral. Brochures and advertisements were printed to herald the arrival of the new, much improved Imme, but ultimately only three prototype R150s would be built.

Image Source

In an attempt to diversify the product line, a step-through scooter called the Till was developed in late 1949. While not as well-known as the Imme the Till offered several innovations of its own. Using an R100 powerplant with duplex chain drive and enclosed bodywork, the Till was notable for using part of the rear frame as the exhaust pipe and having an adjustable rear suspension that compensated for the weight of a pillion - a mechanical switch connected to the passenger pegs engaged an extra spring to support the load of a passenger on the rear suspension. Five examples were built in 1949-1950, along with a single prototype using the R150 twin cylinder engine with an integrated cooling fan. Interestingly a Till 100 was used as a prop in the 1950 West German film “Schwarzwaldmädel” (“The Black Forest Girl”), a sappy bit of romantic entertainment that was part of a genre of escapist movies made in postwar Germany.

Image Source

Even more obscure than the Till was the Zircon moped presented at the Brussels Motor Show in 1950, which used an R100 power unit mated to a bicycle-like chassis made in gents and ladies configurations – whether this machine made it past the prototype stage is unclear, with only a blurb and a drawing from the French magazine “Le Cycle” surviving to prove the existence of this unusual bastardization of Imme components.

Image Source

Despite all appearances of success there were problems brewing at Riedel. The single-sided crankshaft design of the R100 engine was proving problematic – it was fragile, and notorious for destroying its single main bearing. Engine failures while the machines were still within the factory warranty were becoming a major liability for Riedel, and the kickstart mechanism in the gearbox was also proving troublesome. The slim profit margins meant that any warranty repairs, particularly ones that involved major engine work, were incurring significant losses - enough to warrant a redesign of the bottom end of the R100 motor that dropped the single-sided crankshaft in favour of a conventional two-main bearing setup.

Image Source

It proved to be too little, too late for Riedel. The writing was already on the wall, and the company books were suffering under the weight of warranty claims. Mismanagement of the company finances compounded the losses. Despite healthy sales and a total of 12,000 machines rolling off the line Riedel Motoren AG was in receivership by the end of 1950. Norbert Riedel stepped down and company executive Fritz Philipps took control, continuing R100 production into 1951. The Immes produced under Philipps’ direction were christened the Neue R100/D and featured the updated twin-main crankshaft as well as an improved kickstart gear, but were otherwise identical to earlier R100s.

Image Source

While the R100/D addressed the major flaws of Riedel’s engine design it wasn't enough to save the floundering company. Debts in excess of 1 million Deutschmarks crippled the company and there was little that Philipps could do to keep the banks at bay. Production continued until November 1951, when Riedel Motoren AG was finally liquidated. Philipps purchased most of the tooling and founded his own company, Zweirad Motoren und Getriebe (ZMG), to continue limited production of the Imme and provide spare parts support for existing machines. The ZMG Immes used the same chassis as the R100 but introduced an enlarged version of the R150 prototype engine featuring a 174cc, 52x41mm twin-cylinder configuration with a claimed 8.5 hp. Only 25 complete R175s would be built over a period of several years, with a few examples put together in later years by combining R175 engine with R100 chassis. Production of spare parts and a few complete engines continued until 1956, by which point ZMG had produced fifty 125cc singles based on an enlarged R100 D engine, along with ten 195cc, 55x41mm, 12 hp “R200” twin-cylinder engines which would prove to be the ultimate evolution of Riedel’s design. Production of modified gearboxes continued after 1956, and ZMG became Philipps Getriebebau in 1958, which subsequently became Antriebstechnik Roland Schwarz GmbH & Co. in 1995. The company continues to operate today as gearbox specialist RSGetriebe GmbH in Sonthofen.

Image Source

After leaving his namesake company in 1951, Norbert Riedel returned to Victoria where he headed design on the KR 21 Swing motorcycle and Peggy scooter, both released in late 1954. Both were interesting and advanced machines that featured some elements that were clearly a product of Riedel’s design process, an evolution of some of the ideas introduced on the R100. Much like the Imme the Swing and Peggy had their power unit rigidly mounted to the rear swingarm, pivoting within the frame and bobbing up and down in line with the rear suspension - hence the name “Swing”, which was soon nicknamed “das schwebende Motorrad” (“the floating motorcycle”). Both machines used a 197cc 65x60mm horizontal two-stroke single mated to a four-speed transmission with a fully enclosed chain final drive, with the cast alloy chain housing doubling as a structural element of the swinging arm, but differed in their chassis designs – the Peggy had a step-through frame and fully enveloping bodywork (with a fan providing cooling to the enclosed air-cooled engine) while the Swing had a more traditional duplex cradle frame with a half-bathtub rear fender and an exposed powertrain.

Image Source

Both the Peggy and the Swing were notable for offering electric starting* long before the “electric leg” became commonplace in production motorcycles, as well as introducing a unique electromagnetic push-button gearshift integrated into a gearbox that applied the linear shift mechanism introduced by Riedel on the Imme. The system, dubbed Swing-Blitz-Schaltung (SBS), used a four-button gear selector switch mounted on the left hand handlebar which allowed the rider to select individual gears. Four doughnut-shaped electro magnets were arranged in line around the draw-key shaft. When a button was pressed on the selector, one of the four magnets energized and pulled a cylindrical barrel threaded onto the end of the shaft into the position needed to engage the individual gears. As on the Imme the gears were engaged by detent balls arranged within their hubs, pushed outward by a bulb-shaped wedge on the end of the selector shaft to lock the gear.  Neutral was selected by activating both the 1st and 2nd gear magnets, which would hold the wedge between the two positions and allow the gears to freewheel. While ingenious and unique, the system was fragile and prone to failure, easily accomplished if the rider selected the wrong gear at the wrong time.

Image Source

Details of Riedel’s career following his work at Victoria are scant. At some point he left the company to start his own business in Lindau called Amarturen GmbH. There have been suggestions that Riedel faced significant problems in securing royalties and recognition for his designs, with much of his work at Ardie being unrecognized and his draw-key gearbox allegedly copied by several companies, most notably cribbed by one Hermann Hagenmeyer - the founder of GETRAG, which has grown into one of the largest gearbox manufacturers in the world.

Image Source

Norbert Riedel was killed in February, 1963 in an avalanche while skiing at the Zürs alpine resort in Vorarlberg, Austria. He was survived by his seven year old son Steffen, who would go on to write a well-reviewed German-language biography of his father detailing the difficulties he faced as an engineer in postwar Germany.

Image Source

Following the closing of Riedel Motoren and the end of ZMG production, the Imme faded into obscurity. R100s were always cheap, economical transportation and were treated as such – which is to say badly. As the decades passed attrition claimed many of these unique machines, their delicate engines and advanced chassis’ succumbing to the use, abuse and neglect of uncaring owners. A small but loyal fanbase remained in Germany, where the Imme earned a cult following that persists into the present, but most of the 12,000 machines that rolled off the Immenstadt assembly line were lost to history and indifference. This has made the Imme a particularly rare and under-appreciated piece of design, a forward-thinking and beautiful motorcycle that often baffles oblivious onlookers who have never heard of this “bee” machine. Few are aware of the innovative design elements it featured decades before they were re-introduced by mainstream manufacturers.

Image Source

A few modern designers quietly uphold the Imme as a masterpiece of motorcycle design. Former Ducati (and current Confederate) designer Pierre Terblanche holds the Imme in high regard:

"...It is a bike of its time, but it really is a fantastic piece of design... It is simplicity of design at its best, spectacular and simple at the same time. Hopefully someday I’ll track one down to buy and place in my living room as a piece of sculpture."

Bienville Studios JT Nesbitt is happy to expound the virtues of the Imme to anyone who will listen:

"It inspires me, and informs all of the decision making on the current project. The Imme represents the most beautiful economy of design that I have ever seen on a motorcycle. Unfortunately it comes at the expense of real world considerations like unsprung weight, exhaust tuning, and suspension damping... But none of that really matters when I consider that it is the only motorcycle that I truly, truly, want to own. If asked, I would choose it over all others."

Image Source

The Imme received a significant boost in credibility and appreciation after it was featured as one of the centrepieces of the Guggenheim’s “The Art of the Motorcycle” exhibition in 1998, where it was displayed on the merits of its beauty, its design, and its historical context. Today the Imme remains relatively obscure but greatly appreciated by the few who are familiar with it, and the value of surviving examples has been steadily rising (if not threatening the traditional blue-chip hierarchy). Despite the recent rise in appreciation the history of the Imme has been largely lost over the course of decades of anonymity, and few are aware of Norbert Riedel’s contributions to modern motorcycle design. Thus the Imme is one of the greatest motorcycle designs that no one has heard of, a machine out of time and the product of a brilliant man who remains tragically underappreciated.

Image Source

*In 1953 Norbert Riedel patented a combination starter-generator, but it’s unclear if this system was utilized in his Victoria designs. If anyone has any experience with Swing or Peggy engines, feel free to chime in.

Interesting Links
The "Imme Circle of Friends", the most comprehensive source of documentation and information about Immes online
Steffen Riedel's biography of Norbert Riedel
Motorradonline article on the Imme R100
Rebuild of a ZMG R175 engine
ZMG R175 for sale
Imme R100 featured on Bring a Trailer
Norbert Riedel's patent for a combination starter/generator motor
Victoria KR21 Swing Fan Page
Details and photos of the Riedel Anlassasermotor
Riedel Anlassermotor for sale
Synopsis and reactions to "The Art of the Motorcycle" exhibit