«

»

1939 BMW R12

1939-bmw-r-12_2

The BMW R12 and R17, both introduced in 1935, used unique pressed steel frames and may have been the first production motorcycles with hydraulically-damped telescopic forks. Steel pressing equipment BMW used for automobile manufacturing led the company to this chassis design solution through about 1942. It also offered interesting “art deco” styling possibilities. Practical, these bikes had interchangeable wheels.

BMW, or Bavarian Motor Works, was formed about 1916. The first products were aircraft engines. The “boxer” engine layout worked for aircraft keeping the cylinders exposed to cooling airflow. This layout also worked well for motorcycles and BMW built their first in 1923 but previously supplied engines to then current motorcycle manufacturers.

The in-line layout, crankshaft in line with the motorcycle’s length, made it a natural to use a direct connection between the engine and transmission, then a shaft to the rear wheel. In a sense BMW’s time with aviation designs set its path, with few deviations, for the next 75 years. Now BMW uses in-line and transverse fours, transverse twins and singles and even belt drive! But shaft-driven boxers, now even liquid cooled, remain a mainstay in the model offerings.

With the introduction of the R11, BMW began using a new frame made of left and right side pressed steel halves riveted together. With common use of sidecars previous frame designs sometimes fractured. Though it’s pressed steel design reminds us of the earlier leading link designs, with the R12 also came hydraulic front suspension. Sprung seats were all that was offered to damp bumps at the rear of the motorcycle.

When you visit the National Motorcycle Museum you can view many great European bikes including early BMW’s, a rare Opel Neander, a Husqvarna V-Twin, Ducatis, Moto Guzzis and Aermacchis including the 175cc Chimera which won the motorcycle class at the Pebble Beach Concours d’Elegance in 2011.

Specifications:

  • Engine: Four Stroke Opposed Twin
  • Induction: Side-valve Heads
  • Bore & Stroke: 78mm x 78mm
  • Displacement: 745cc’s
  • Carburetion: Amal 6/406SP
  • Lubrication: Pressurized/Wet Sump
  • Horsepower: 16HP
  • Clutch: Hand Operated
  • Transmission: 4-Speed/Hand Shift
  • Ignition: Battery/Optional Magneto
  • Electrics: Bosch Generator
  • Frame: Pressed Steel/Double Loop
  • Suspension: Telescopic Fork/Rigid Rear
  • Wheels/Tires: 3.50 x 19 / 3.50 x 19
  • Brake/Front: 200mm Drum
  • Brake/Rear: 200mm Drum
  • Wheelbase: 54.5 Inches
  • Weight: 410 Pounds
  • Top Speed: 68 MPH
<
>

5 comments

Skip to comment form

  1. Daniel Kutt

    BMW was ahead of its time. It was a beautiful machine. I ride a 2004 R1150RT today and it is a beautiful machine.

  2. Mark

    Please add some more information to this article. What is the procedure for shifting with both hands? Hand clutch, hand shift, hand throttle? Also, the speedometer shows the top speed in second gear to be 65. Is that KPH? If so, the red line is only 83 KPH or 51.6 MPH. The performance for a 750 cc. twin with a four speed gearbox should be much better than this even in 1939. The top speed is 68 MPH? Thank you for the articles.

  3. Mark

    Mark,

    Thanks for the note. I have not ridden this motorcycle, but I’ve ridden hand shift/foot clutch Harleys and Indians; they both require a lot of coordination, maybe the BMW moreso as neither foot is part of the shifting operation. Like the big antique American bikes, shifting was more what you’d imagine in an old truck; slow and deliberate and throttle was pretty much closed to shift. Right hand is on shift lever, left hand on couch lever. Luckily along the line “inventors” have brought us foot shift, smooth throttles and clutches and shifting is quick and smooth. I suspect not so in this 80 year old machine.

    18HP moving 410 pounds sounds like about 70Miles Per Hour (Speedo in KPH, I believe.) I think to exceed 100mph on this heavy a bike you’d need at least 30HP and be tucked in.

    Also, the data in most of our Featured Bike stories is derived from published material, books, websites, manuals and such. Most of the Museum’s bikes are “mothballed” so we do not weigh them, and go out and make a run looking for top speed. That would be nice, but there are not enough hours in the Museum day. When we do get a chance to ride old machines we take advantage of the opportunity. Like this BMW, they are so much more engaging and demanding of concentration and experience to make them work well. Involving, which is a good thing in today’s world.

    Thanks for writing. I hope I’ve shed a bit of light on your questions.

    Mark
    National Motorcycle Museum

    1. Mark

      Mark,
      Thank you for your insight into this fascinating world. When you do have the opportunity to start, ride, and shift a museum piece I’m sure we would love to see a video of the “event”. An instructional video or a tutorial would be intriguing to some of us who only know left hand clutch shifting techniques. My own personal experiences with variations in shifting include some different shift patterns and some Triumphs with right foot shift levers.
      Sincerely,
      Mark

  4. Chuck Thomas

    I rode with the AMCA on a San Diego County ride a few years back, and was impressed with the skill set it takes to ride a 1930′s technology motorcycle. Right throttle, hand shift, Left throttle, hand shift, foot clutch’s…. ( IT WAS FUN TO WATCH ) OH YEAH !!!!!!

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>