Rennsport

Some time ago I shared a number of photos of BMW Works kompressor bikes.  These are mostly in museums, with a handful in private collections.  I thought I would also share some pictures of Rennsports or RS54's.

In 1953, BMW introduced a low number production race bike.  It was intended for serious privateer racers.  The machine ultimately produced was the evolution of a series of engines based on the overhead cam design. This design exercise began in the late 40's, and arose from the need to find a replacement for the aging pre-war kompressor motors, which ceased to be as effective when the FIM banned supercharging after the war.  For a nice description, reference the book "BMW Engines" by Dr. Karlheinz Lange.

The original production of RS54's consisted of approximately 25 bikes.  These were long stroke machines, having a bore of 66 mm and a stroke of 72 mm.  The bikes were originally equipped with a 4 speed gear box. 

Later developments lead to production of a short stroke machine with a bore of 70 mm and a stroke of 66 mm.  The shorter stroke motor revved higher and provided more horsepower.  The short stroke motor was initially used on the works bikes, but was successfully utilized later by quite a number of sidecar racers who took home a long string of championships in the 60's and 70's.

Here is an early photo of a pre-production or works model.  Several differences are evident when compared to the bike that was ultimately produced as what we now refer to as the RS54.  This particular bike is colloquially known as the "Zweibolzen".  Note that there are "two bolts" fixing the valve covers to the heads.  The later RS54 utilitzed four bolts.  The motor is actually quite different in form.  Also note the telescopic forks fitted here.  Ultimately, a decision was made to utilize the Earles fork on the production RS54.  A year later the Earles fork also showed up on the newly redesigned sport and touring models, the R50, R60 and R69.

Above pictured is a restored Zweibolzen from the collection of Franz Amering in Austria.  Photos from MVCA.at.   The frame pictured here appears to be a modified plunger frame.  As we will see shortly, the production RS54 utilized a totally new frame design with a rear swingarm that enclosed the driveshaft.  However, unlike later civilian models, the rear swing arm of the RS54 does not contain oil. 



Period photo of Zweibolzen Type 253 motor. Copyright Wil Elbers.

The Zweibolzen motor was further developed and refined, ultimately into the production RS54 of which somewhere around 25 were built originally. 

Perhaps one of the most original appearing bikes in existence today belongs to BMW and is housed at the BMW Classic building on BMW Allee just off Schleissheimerstrasse in Munich.  I had seen and photographed the bike there on a prior occasion.  I saw the bike again at the Saisonstart Open House at Niederlassung BMW.  Its a nice event they throw each year to kick off the riding season in March.

I do not know if this bike is one of the original 25 or not.  I suspect it isn't, but rather a very fine bike produced later but to original 1954 trim. This particular bike has a four speed gearbox.  The original long stroke bikes were equipped with a four speed gearbox, while later short stroke bikes are usually seen with a five speed gear box attached.

It is difficult to tell outwardly whether it is a long stroke, or short stroke motor.  I'm sure someone more knowledgeable than me might be able to tell. 

The tank is of beautiful form and held in place by a long metal strap running fore and aft, under which is a rubber strip which protects the paint from the metal.



Wonderful little VDO tachometer.  Many RS machines seen today have a Smiths ATRC tachometer mounted.  Perhaps they were more accurate or reliable.



The tachometer drive comes in two forms.  The solo machines most often utilized the a tach drive from the breather, while sidecar machines often drove the tach from the crank nose.



Earles fork front end.  2LS front brake.  Notice the spoke nipples are at the hub side, while the spoke head is at the rim side.  A unique feature not found on other BMW of the same period.



The carburetors are 30 mm Amal Fischer. 



Nice photo of aluminum tube housing the bevel shaft which drives the overhead cams.

Going on a diet

The motorcycle racers of today have at their disposal a host of exotic materials by which to make parts lighter, and even stronger as compared to the past.  Titanium bits and pieces are ubiquitous in todays paddock. 
Carbon fiber has revolutionized motorsport, and has even found its way into production bikes.  (ie the HP2 Sport). 

Guys racing before such exotic materials were available resorted to more practical solutions for decreasing the weight of a bike.

Of course a race bike would not have the routine road going accoutrements such as lights, horn, signals, etc.  Casting material for many bikes differed from the pedestrian models as well.  Elektron, a magnesium alloy, was used extensively on works bikes and even by privateer racers before and after the war. 

Any part on a bike that could be lightened, while maintaining its integrity, was subject to a diet.  For sheet metal parts, this often meant drilling holes to reduce the amount of material.  Simple things like changing a steel drain plug to an aluminum one, would amount to a small reduction in weight.   But when multiplied by the number of plugs on the bike, could add up to real savings at weigh in.

Pictured above are two drain/fill plugs. They are M14 x 1.5.  The plug on the right is a standard issue item found on most pre 1969 BMW motorcycles.  It is SW 19 (SW = schlüsselweite = width across flats, or wrench size).  Material is steel, cadmium plated.

On the left is a "lightened" racing version.  While still the same thread diameter and pitch, the length is slightly shorter, and it is SW 14.  The material is aluminum.  

The steel plug weighs in at 29.3 grams, while the aluminum plug weighs 6.8 grams.  (A 77% reduction in weight.)  If you multiply by 5 (the number of plugs on a transmission, final drive and oil sump), the weight savings is a quarter pound.  Not huge, but the effect is additive when other weight saving meaures are employed.

BMW R68 Operating Instructions

As most BMW motorcycle aficionados are aware, the R68 is arguably the most sought after vintage post war production motorcycle.  With it's introduction in 1952, BMW brought onto the motorcycle scene a 600 cc sport bike that would do over 100 mph off the show room floor. 

Produced in relatively small numbers (total production for 3 years was 1,452), the model was discontinued, or rather evolved with the introduction of the R69 in 1955. While the R69 motor was more or less maintened in its original form from the R68, a new gearbox was fitted, finally doing away with the auxillary hand shaft on the starboard side.   The chassis was significantly overhauled to include the Earles fork front end and hydraulic dampers in place of spring-only rear suspension. 

When the R68 originally came out in 1952, there was no owners manual specific to the bike.  As such the owner was given a manual for the R51/3 and R67/2, along with a cardboard fold out supplement specific to the R68. This changed late in the production run when a proper hardbound R68 manual was printed. 

The paper "supplements" are extremely rare.  The photo below depicts the English and German versions.  I have included photos of all of the pages from the English version. 

If there is interest, I may be persuaded to invest more time in making proper digital scans. In the meantime, enjoy the photos.

The "Operating Instructions for the BMW Motorcycle R68" outlined all of the specifics that were unique as compare to the R51/3 or R67/2.

Unique to the early bikes from 1952 are the black front fender stays. Metal shrouds as opposed to rubber gaiters on the forks.  Eberspacher air filter and swallow tail mufflers.  The bike has half hub wheels with chrome rims.  These features change in later iterations of the bike.

Magura rennhebel und gasgriff

The MAGURA company has been around for over 100 years and has been partnered with BMW since the first motorcycle rolled of the line in 1923.  The company, which is now involved in mountain bike components as well, has long supplied the clutch, brake and throttle controls for all manor of BMW motorcycles.

Beginning in the 50's (and possibly before), MAGURA controls were used on race bikes, in addition to civlian models.  While the civilian models were often heavier, clunkier cast or forged pieces incorporating various switches and levers. The race models were considerably lighter, and served a single purpose. 

The clutch and brake levers (hebel) were made of flat aluminum stock, bent over a form and drilled, whereas the civilian models were a heavier forged part.  The perches where light, and almost delicate in appearance, and the throttle was simple, but effective.

Seen here is a racing or quick throttle, brake lever and kill switch mounted on the aluminum drag bars of the R51/75 racebike.

Note the rather simple and lightweight brake lever mount, with a simple clamp to attach to the bars.  You can also see from the picture the hollow nature of the lever itself.  Adjustment was rather simple.

"Sport" version

"Race" version

Pictured above are two version of the adjuster mechanism.  I'll refer to them as the "sport" version on top and the "race" version on the bottom.

To adjust the clutch or brake cable with the sport version, one simply loosens the knurled ajustment sleeve until the correct amount of play in the cable is achieved, then the larger diameter knurled nut is loosened away from the hex nut and is used to lock the adjusting sleeve in place.

The "race" version allows on-the-fly adjustment without the rider needing to stop, or even slow down.  The cross shaped adjustment wheel has 4 detents, such that 4 clicks will move the adjustment sleeve in or out by one thread length (depending on whether its moved clockwise or counter-clockwise). 

NOS Magura racing throttle

Notice that the tip of the lever comes to a point.  It's actually surprisingly sharp, and one could imaging that in a bad motorcycle accident, especially on the track, the lever could easily impale someone.  Whether or not this actually happened, I have no idea, however by the late 60's, the sanctioning bodies outlawed the use of these blade type levers. 

Rather than replace them, enterprising racers would weld a ball onto the end.  Civilian models were changed to add a ball on the end as well.  With the BMW R50 and R60's, the changeover occured somewhere around 1967 or so.

Note the round, aluminum balls welded to the tips of the Magura racing levers on this 1954 RS54.

ISDT VDO Clock

When it comes to post war BMW accessories, none seems more coveted than the VDO handlebar clock.  This rare accessories is found is a couple of different styles including gold face, or as pictured here, with a black face. Originally used by racers of the day, today they seem to be the holy grail of the "BMW Bling Hound".   Rarely do you see one mounted to a bike that isn't also accompanied by a tachometer, and a Hella spotlight/mirror. 

The five (5) jeweled movement was housed in a rubber ring to help decrease shock from the bouncy ride.  Note the red hand on this model actuated by the center nob to help record section or lap times.

These occaisionally come up for auction or sale.  The black face seems more desireable than the gold, as they obviously match better with other instruments on a classic BMW such as the speedometer or tachometer.

For more pictures, information and discussion of VDO clocks, check out the website of fellow collector James Young by following this link. http://www.earlesfork.com/gallery_3.html

Dana Point Concours

The Dana Point Concours d'Elegance was held at the St. Regis resort this past weekend here in lovely Southern California.  The weather was spectacular.  The event is an up and comer with the motorcycle crowd.  It has been a fantastic car show for the past 29 years.  Last year they added motorcycles to the event for the first time. 

Being that the show is practically in my backyard, I decided to bring a bike to the event.

The R60/2 pictured below languished outdoors on the side of a guys house for about 25 years.  This is a case of being in the right place at the right time.  The guy offered the bike to me free of charge if I would haul it away.

It was not in too bad of shape.  The top end was missing and the tank was gone.  All numbers matched, and I figured it worthy of restoration.  Luckily whoever obsconded with the top end left some oily rags to plug the sides of the crankcase.  Oil was left in situ, whiched helped to preserve the crank.

I restored the bike using many NOS parts.  It is a correct restoration down to the original fasteners.  I opted for the high bars because all of my other bikes have the lower bars, and these were in fantastic shape.  The paint is single stage Glasurit, and the stripes are hand done.

I generally don't add excess "bling" to bikes, but the Hella "eyebrow" style headlight bezel looks sharp.  I acquired it along with some other parts a few years ago, and figured it would look best on the R60. 

Aftermarket hubs for BMW plunger frame bikes.

In the 50's and 60's there were several companies in Germany and the US providing aftermarket parts for BMW motorcycles.  Notables from Germany include the firms of Ernst Hoske and Georg "Schorsch" Meier.  Both turned their passion for racing into business ventures.

One of the parts offered by both Hoske and Meier were aftermarket hubs.  As the plunger frame bikes up to 1954 utilized a 200mm half hub design, the width of the brakes on the stock machines was quite small.

Hoske offered a replacement full width aluminum hub.  Unlike the factory hubs which were fitted with drive splines front and rear, the Hoske front hub deleted the drive spline to save weight. 

The Meier hubs are also full width and made of aluminum.  The front and rear hubs are identical with a drive spline in both.

Hoske also made lightweight versions out of Elektron (a magnesium alloy).  However when found today, these are often very corroded or have cracks in them. 

Complete wheel with 19" high lip Weinmann rims, and half polished Meier hub.  Note the center is the same rough cast finish as the motor, trans and final drive.



Notice from the Meier Prospekt that the hubs were offered in three varieties, matte finish, partly polished or polished. 




Here is an example of the Meier full width hub in full polished form.


 Below is a photo (albeit not a great one) of the Hoske firms Prospekt for racing parts.  I have shown the page describing the available wheels, hubs, brakes, etc.

Here is a front hub and brake setup. This is a dedicated front hub as you'll note there is no drive spline.  Pictured is a standard simplex front brake plate.  The shoes are wider than standard.

Hoske rear hub.

Same hub as above from the outside.  I have seen two variations of this hub.  Some have the bolts going all the way through with cap nuts on the outside.  I have also seen variations where the bolts don't go all the way through, thus from the outside, the front and rear hubs look the same. 

You will notice that the Meier hubs use a bent spoke, while the Hoske hubs use a straight pull spoke.  Both the Meier and Hoske hubs are equally desirable. 

Schorsch Meier R51/2

Here is a project I am currently working on.  The posted pics are of the bike at the time I purchased it a few years ago.  Its an interesting bike, one that I like to refer to as a gentleman racer.  Obviously not a works machine, it started life as a civilian model, but then had some nice, and interesting upgrades added.  It looks to me as though someone went through the Schorsch Meier catalogue and bought nearly one of everything and put it on the bike.  It has high compression pistons.  The final drive gearing is standard.  I haven't yet torn open the gearbox, though I suspect it may be standard as well. 

For now I will post pictures of the bike as I found it.  I will later add some photos of the restoration that is underway.  Comments welcomed and encouraged. 



Schorsch Meier full width aluminum hubs front and rear.  Schorsch Meier racing fender.  Faltenbalge in place of metal front shock covers.  Rare Schorsch Meier/Lugauer racing gas tank.



Patina!

Note the matching front and rear hubs.  These came with either a rough cast center section or full polished.  These have the rough case centers which look nice, and match the engine and transmission cases.  The keen eye will spot the Magura Rennhebel (racing levers).  Don't think I'll be keeping the high bars!

Rare 19 inch high lip Weinmann rims.  I've never seen another pair of high lip in the 19 inch diameter.  Obviously wrong valve covers.  I'm looking for original ones in good shape if anyone has any.



More patina.




Grease is a great preservative.  I am thankful that people don't clean old bikes before they let them sit for years.


I am part way through this restoration.  The wheels are rebuilt.  The bike is completely broken down.  Next step is to have the frame and forks painted, and then I can put a rolling chassis back together. 

Unfortunately I only know the history back about 30 years.  It was owned by Rick Monahan of Black Kat in Venice Beach, CA from the early 80's until around 2001 or so.  Before the 80's not much is known.  I do not know if it was raced or was simply a sporty daily rider.

PROGRESS:

Progress on the restoration is slow, but proceeding.  The frame and fork parts are now in primer.  The Meier front fender has been straightened and primed. 

The front fender is a little bit different than the stock.  For starters it is not valanced, and is considerably lighter.  It is much more like an R68 fender than an R51/2 fender.  Furthermore it is attached to the fender stays by chrome clips which are bolted to the fender.  Of course when I got it one of the clips was missing and the others were bent or rusted. 

A tool and die maker friend made up a die and we made new clips. 

BMW Kompressor

Not too much commentary for these bikes.  Enough has been written in various publications about the history of the bikes, and their triumphs before the war when the use of the Kompressor was still sanctioned.  Here are some assorted pics of various BMW kompressor machines with close-up detail you can't find in the books.  The first bike is in the BMW Museum in Munich.


Aluminum bars. Split fuel tank with left and right sides that bolt together in the middle. R. Muhle tachometer.

 

As is commonly known, the so-called plunger frame bikes have no true dampening at the rear.  There is only a spring on the left and right.  As such, many works bikes incorporated a friction dampener to the rear to try to combat some of the bounce.  Hidden in this photo behind the rear spring is a metal post that runs from the rear axle to the rear arm of the scissor dampener which you can see mounted to the rear frame tube.  Just like the steering dampeners, one can increase or decrease the amount of friction by tightening or loosening the knob.  The same round friction disks were used for the steering and the rear suspension. (The vertical metal post and tube attached to the axle in this picture are for suspending the bike as part of the display at the BMW Museum.)

Notice on the rim the four dots.  These are rivets where the rim was seamed together.  This is a steel wheel.  The R51RS used a similar seam and rivet design, although in aluminum.



Notice the removeable frame reinforcing tubes on the side of the frame.  Attached obviously with bolts as there removal is required to pull the transmission or motor. The rear set of pegs is obviously not for a passenger!





Single Amal Fischer carburetor feeding the kompressor.





Sprung drilastic saddle.  Partial view of "rennbrotchen". 





Accomodation for spare plugs, including wrench.  Actually the plugs weren't spares.  They used one heat range for warm up and another for the race.  This backfired, no pun intended, at one important venue when the threads in the heads were stripped while attempting to swap the plugs right before a race. Bosch FJ2 type magneto.  Note that the crank case, and transmission are made of Elektron, a light magnesium alloy.

 



"Lightened" brake pedal and hand shift lever.

 This next bike is in the collection of the Zweirad Museum in Neckarsulm, Germany.  It's a bit of an amalgamation of parts, some things were changed over the years, such that its not all period correct.  Still, any BMW collector would love to have it, including me! These practically never change hands.

Nice view of the "Koenigswelle" or King Shaft that drives the overhead cams via bevel gear.  Amazing that this is 1930's technology.  It was reintroduced in the 1950's with the RS54 and its precursors.  And the design was recently used again with the latest generation of DOHC motors used on the HP2 Sport and subsequently the R1200GS.

The third bike is one that was, for a time, here in the US.  It was sold a couple of years ago to a wealthy collector in Germany.  The last time I saw it, it was in a thousand pieces being reverse engineered to make a small series of replicas. 

The fourth bike needs no introduction, the ex-Meier, ex-Surtees 1939 TT winning kompressor in the collection of BMW in Munich.