Recognisably a BMW, but a rather rare sight today. Alan Cathcart tells the tale of a very early flat twin
Recognisably a BMW, but a rather rare sight today. Alan Cathcart tells the tale of a very early flat twin
The early days of BMW AG exactly a century ago saw it born of a struggle for survival, after the 1918 Treaty of Versailles which ended World War 1 banned the manufacture of aircraft in Germany. BMW (as in Bayerische Motoren Werke AG) had been founded two years earlier in a reorganization of Rapp Motorenwerke, a Munich-based aircraft engine manufacturer, so to stay alive it was forced to turn to making industrial engines, agricultural machinery, toolboxes, office furniture, and then finally, in 1923 – motorcycles.
BMW’s successful struggle to survive was largely funded by Italo-Austrian banker Camillo Castiglioni (no relation to the current owner of MV Agusta), who was acclaimed as the wealthiest man and most influential financier in Central Europe during WW1, and who until 1929 was President of BMW AG. In 1921 BMW had begun manufacture of its M2B15 flat-twin motor, originally designed by its chief engineer Max Friz as a portable industrial engine. It was also used in motorcycles such as the Victoria and the Helios, which gave
BMW the inspiration to build its own bikes. So in 1923 the R32, the first motorcycle to be badged as a BMW, was launched. It featured a 486cc wet-sump side-valve engine with horizontally opposed cylinders and shaft final drive, a flat twin layout which would forever be associated with the marque.
The R32 was the prototype for all future Boxer-engined BMW motorcycles, and employed a tubular steel rigid frame, like its successor models the R42 and R52. These also featured 500cc side-valve motors like their ancestor, but BMW also developed the higher performance ohv R47 and R57 500cc duo. 1928 saw the appearance of BMW’s first 750cc models, the side-valve R62 and ohv R63. The latter remained the sportiest BMW built until the end of the 1920s, with an output of 24bhp and a top speed of over 75mph, while like its humbler sister still maintaining the tubular steel frame, with leaf-spring front suspension.
Unhappily, this frame design was increasingly causing reliability problems across BMW’s entire model range, particularly when a sidecar was fitted. This was becoming increasingly popular, especially on the R62, both for family use, but especially by the Wehrmacht (the German army), even in the days before Hitler came to power in January 1933. The increased power and especially torque of each new generation of BMW engines, coupled with the extra weight of the sidecar’s payload – which in military use frequently saw two armed soldiers being carried aboard the motorcycle, and often a third on the sidecar, complete with the weight of their rifles and sometimes a machine-gun and ammo – led to the frame fracturing, usually around the steering head, where the welds just weren’t up to the job of supporting all that extra weight. The girder forks also had a propensity for collapsing, so something definitely needed to be done.
At the Berlin Show in November 1928 BMW displayed an entirely new method of constructing its motorcycles’ frames, the origins of which lay in its acquisition the previous year of the Dixi car company, then making Austin Sevens under licence from the British manufacturer. Dixi’s factory in Eisenach – later, after ending up in the DDR post-WW2, to host production of Wartburg cars powered by a three-cylinder two-stroke engine derived from the British Scott-3 motorcycle’s powerplant – also produced railway equipment and track, which necessitated the installation of massive 1000-tonne hydraulic presses.
So not only did BMW continue making the Austin Seven – rebadged as a BMW Dixi, which thus constituted its entry into the car
market – but it also evolved a completely new range of pressed-steel chassis made at Eisenach for its motorcycles, both twins and singles. It would continue using these right up until 1942, when it reverted to circular and oval-section steel tubing for its motorcycle frames.
These new much more robust pressed steel chassis equipped the two new 750cc models launched at the Berlin Show, production of which began in September 1929 at a retail cost 5% higher than the steel tube-framed R62/R63 models they replaced carrying the same engines, albeit with a 10kg weight penalty for the more durable construction of their double-cradle rigid frames. One of these was the 735cc R16 ohv twin replacing the R63, 1106 units of which would be built in the next five years, alongside its sidevalve sister, the 30% less expensive 745cc R1, which superseded the R62.
Progressively improved year on year, in an early demonstration of what would become BMW’s traditional development strategy, the R11 was built in five different series up to 1934. Exactly 7500 examples of this relatively austere but workmanlike model were manufactured for both civilian and military use before it was replaced in 1935 by the R12. This used the same 745cc sidevalve motor, and as such it represented BMW’s first volume production model. The workforce at BMW’s Munich factory rose to 3000 by the early 1930s once R11 production was in full swing, coupled with a further 1500 at Eisenach, albeit also building Dixi cars and railway equipment.
BMW’s relatively vibrationfree flat-twin engine was already noted for its smoothness and refinement. Coupled with its three-speed shaft-drive transmission and new, more rugged frame and front suspension, this made the sidevalve R11 one of the most popular large capacity motorcycles of its time in Germany, especially with its vaguely Art Deco styling with a black paint scheme and white pinstriping. Notwithstanding its reduced horsepower compared to its ohv sister – the R11 produced 18-20bhp depending on the year, against the ohv R16’s 25-33bhp – the more humble of the two models sold best. It was no doubt aided by that lower price in delivering substantially increased torque versus its ohv sister model, as well as the reduced manufacturing costs of a simpler sidevalve motor and easier servicing thanks to the reduced complication of its valvegear.
Besides the frame, BMW also used steel pressings for its new bike’s trailing-link fork. The F66 chassis for the R11 consisted of two large pressings, one for each side of the frame, riveted together at the steering head to form a twin-loop double-cradle chassis, with strengthening cross members mounted across the top of the engine. Substantial gusseting further reinforced the steering head, and provided a place for BMW to position its already famous blue and white roundel badge. The separate 14-litre fuel tank was positioned within the frame and
protected by the large gussets, so it was well shielded in the event of a fall in any of the arduous cross-country trials and races the bike was entered in, often with a sidecar attached, let alone in military use.
Fitted with what would become BMW’s familiar transverse kickstarter that had been introduced on its Boxer twins for 1928, the R11 also featured many neat touches. These included the toolbox contained within the gearbox casing, just below the kickstart mechanism, and the cast alloy footboards front and rear – the latter in case a passenger seat was substituted for the luggage rack fitted as standard. BMW was also a pioneer in the use of a central stand as on the R11, rather than the less convenient rear stand which had to be clipped onto the mudguard before departure. 19-inch wheels were fitted front and rear – again, an avant-garde decision by the standards of the day, rather than the more commonplace larger diameter but narrower rims.
The R11’s trailing-link fork was also composed of steel pressings, with a tubular steel loop running from the axles, up and over the substantial and quite deeply valanced steel front mudguard, to operate the sixleaf laminated spring which constituted the front suspension. There was initially no damping, before the fitting of an adjustable friction damper to the fork for 1932. Braking was provided by a 200mm single leadingshoe front drum, but rather than a rear brake located in the wheel, BMW curiously mounted one acting on the transmission final drive shaft, initially with 37mm shoes in a three-rib housing before these were increased in size for 1930 to 55mm, in a fourrib casing.
Weighing 183kg dry, with an unusually forward-looking 53/47% frontal weight bias, in spite of its increased cubic capacity the robust and solid-looking R11 was however somewhat of a sluggard, with a top speed which never exceeded 62mph during its five years of production, against its costlier ohv R16 sister’s eventual 78mph in 1932 guise onwards.
The Typ M56 flat-twin sidevalve engine powering the R11 measured a very modern square 78 x 78mm for 745cc, and was a carryover from the previous tube-frame R62 model, with cast iron cylinders mounted on a light-alloy crankcase, and the 2.5-litre
oil supply carried in the sump, rather than in a separate oil tank as was then almost ubiquitous elsewhere. Running a lowly 5.5:1 compression ratio and originally fired by a Bosch magneto (lighting was an optional extra) it produced just 18bhp at 3400rpm, albeit with plenty of low-down torque. That torque was a key reason for the R11’s popularity, especially in sidecar use, coupled with a 3-speed gearbox with hand-shift on the right and shaft final drive via a singleplate clutch.
Initially, the R11 was fitted with BMW’s own triple-jet 24mm carburettor serving both cylinders, although for 1932 and the thirdseries model this was replaced by a bought-in same-size Berlin-made SUM CK3/500 carb, which aided cold starting by having preheated secondary air drawn through a tube from the exhaust manifold. In due course, in 1934 the final version of the bike finally featured twin carbs, a pair of 25mm Amals made under licence from the UK by Fischer in Frankfurt. This also had the hand gearshift lever mounted closer in to the fuel tank, operating within a pad attached to the top of the frame.
The R11’s lengthways crankshaft originally featured twin-row big-end roller bearings, but for 1933 this was replaced by singlerow caged rollers. The following year the final fifth-series version of the M56 engine saw the camshaft now driven off the front of the crankshaft by a quieter roller timing chain instead of gears, and it also featured battery and coil ignition for the first time on a BMW motorcycle. Coupled with the twin Amal carbs this increased power to 20bhp at 4000rpm (there was still a less powerful single-carb version made for the Wehrmacht), and a few R11 Series 6 motorcycles were also built with a four-speed transmission, as a precursor to the R12 which replaced it for 1936 – still with a pressed-steel frame, but with the added benefit of the first telescopic fork with hydraulic damping.
With 7500 examples built over its five-year production span – a significant number for any manufacturer back then – the BMW R11 isn’t that much of a rarity nowadays, but it is an important landmark in the development of Germany’s largest manufacturer. It even has a recent claim to movie stardom, with an appearance in Wes Anderson’s 2014 film
The Grand Budapest Hotel set in the 1930s, as the bike ridden by Willem Dafoe’s hoodlum character J.P. Jopling. A fine example of the first series 1929 model is to be found in the Sammy Miller Museum on Britain’s South Coast bearing frame no. P1450 and engine no. 65542 – early numbers denoting that it comes from the very first year of production.
The chance to take it for an afternoon spin provided a window on the world of the early-30s, when robustness and durability were keen attributes of BMW’s line-up that were appreciated in export markets like Italy and France, as well as in Germany – and the UK, where this bike was delivered new, as attested by its MPH speedo by VDO.
To start the R11 you must follow a procedure introduced only the previous year by BMW, which later became commonplace on all their models. Put it on its easy-on/ easy-off centrestand, then stand on the left side of the bike, tickle the single carb until it’s properly flooded, retard the ignition via the left twistgrip, pull out the kickstarter attached to the rear of the gearbox from its place tucked away under the seat above the large Exide battery, then kick with your right foot while working the right twistgrip’s throttle to catch it as it fires into life. With its lowly 5.5:1 compression the R11 is easy to start, with a pleasant but subdued though still distinctive crack from the exhaust, which could only be from a flat-twin BMW with its 180° crank.
Climb aboard the comfortable Ragusa rubber seat, which has enough travel in its springs to obviate the lack of any rear suspension, look for the cast-alloy footboards nestling beneath the well-finned cylinders, grasp the wide handlebar which gives heaps of leverage for hustling the BMW through city streets and winding country lanes, grab the light-action clutch lever on the left, and engage bottom gear by pulling the gearchange lever up and back with your right hand. However hard I tried I couldn’t avoid graunching the gear as it went in, but being super low – probably to take account of carrying three soldiers and a tommy-gun! – it was soon time to change up to second by pushing the lever down and away from me, and that was much smoother, ditto the shift to third (top) gear. The R11’s sidevalve engine is so torquey that it was very happy to stay in top gear even for slow 15-20mph bends, requiring no clutch slip to motor cleanly away from a slow speed, up to the comfortable 50mph cruising speed.
I’d expected this vintage BMW to have a relatively modern feel, but instead the riding position was a little curious, with the seat down low and handlebar quite high. Although the long footboards let me put my feet where I wanted to, there wasn’t quite enough space for me to use the forward section, else the toes of my boots would have been burned by the heat off the cylinders as I wedged them in. Not sure how Wehrmacht
feet could fit in there – sorry about the spit’n’polish toecaps on your boots, Fritz!
You want to avoid bumps in the road surface wherever possible, with no rear suspension and a practically rigid front end as well. Those laminated leaf springs didn’t have a lot of give in them, so the BMW front end would hop in the air if you hit a serious bump. The 200mm front brake worked pretty well, which was fortunate since the rear transmission brake was quite ineffective – no wonder they increased the width of the shoes after this first-year model.
The debut of the R11 model exactly 90 years ago this year came at a time when the onset of the Great Depression in the USA had produced a severe shockwave in Germany. Unemployment grew rapidly, reaching 4 million by 1930, and it’s something of a miracle that as many as 7500 examples of this model were manufactured – and sold – during a period of massive recession in its home market, up to and including the end of its production in 1934, during a time when Germany’s post-war Weimar Republic was crumbling. But the fleets of such BMWs in military guise equipped with sidecars became an ever more regular feature of Hitler’s rule – such as the 400 R11 sidecar outfits carrying 1200 Wehrmacht soldiers between them, which paraded past the Führer in Berlin on April 20, 1936 to celebrate his 47th birthday. Within four years they would be used on the battlefields of Europe, many of them never to return. Sammy Miller’s survivor has spent all its life in Britain, as a demonstration of German series production excellence at the most difficult time economically in the modern era – well, up until 2008, at least…
Imagine, if you can, riding one of these on UK roads in 1929. Continental machinery was considerably different to most of the home offerings A glimpse inside to show the workings
Above: Power is delivered by a sidevalve flat twin, while rider comfort is provided by awesome cast alloy footboards and a sprung saddleRight: Lots of bikes get described as ‘motorcycle art’. Well… we reckon that this is certainly that! Inside the engine. Simple enough, and neatly effective
It might be true to suggest that operating the BMW’s hand shift did not come entirely naturally… The 1930 Italian BMW enduro team, with two ohv R63 750s on the left and a solitary R11 sidevalve to the right
That front end again, showing the trailing link design and the 200mm front brake worked ‘pretty well’ Above: Shaft drive (of course), hand shift for the three speed gearbox driven by a big twin. All wrapped in a pressed steel frameLeft: Possibly the most remarkable feature of all lives at the front, where the wheel’s suspension is provided by a laminated leaf spring controlling the trailing link
Right: The rear wheel itself doesn’t carry a brake. Instead, there’s a transmission brake living inside the finned casing where the drive shaft attaches The fuel tank contains both the fuel filler (complete with an internal filter) and the speedo, and is itself contained inside the top frame rails
Some concentration is required until familiarity begins to grow. Chilled ankles would never be a problem here…