13 replies to this topic

[Sergio]

Many years ago, I heard a story of a two-stroke engine in a Formula 3 car that won the Championship. Despite my surprise, in those pre-internet days, I parked the information. These days I'm researching a history of the post-war two stroke engine and in doing so much more meat has been added to the above bone.

 

Daniel Zimmermann was a German engineer who shone like a Supernova for a short time in German motor racing folklore. It was his misfortune that after WW2, he established his own small engine reconditioning shop in his home town of Luckenwalde which was in the Russian Zone. In 1948, the Russian Zone became East Germany. Racing gradually returned to East Germany after the Hitler war and in 1949, Zimmermann spectated at his first race event, around-the-houses races at Wittenberg in 1949. Combining car and motorcycle racing was extremely common in Germany and Wittenberg wanted a slice of this extra action. So the 1949 event included a demonstration 'race' for the new F3 500cc racing car class. But Zimmermann came away disappointed that most of the racing motorcycles relied on West German or British engines. He was determined to build his own F3 car and his own F3 racing engine and he started the project in the winter of 1949-50.

 

The chassis was not particularly noteworthy but its engine was a water-cooled 500cc twin cylinder disc-valve two stroke. It incorporated rotary disc valves (which Zimmermann later patented) which allowed asymmetric intake timing. His engine included roller bearing big and small end bearings, Schnuerle type loop scavenging and a Kuechen style 'third' boost port.

 

Zimmermann first raced the car himself at Dessau in October 1950 and scored a DNF. He must have realised that he was better at spanners than behind the wheel because for 1951, he employed a local driver, Werner Lehmann (not to be confused with Willy Lehmann the East German F3 Champion for several years).

 

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Werner Lehmann racing the Zimmermann F3 car in 1951
 

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Daniel Zimmermann in his 1951 500cc Two Stroke F3 car

 

On 21st April at Round 1 of the East German Championship at Halle-Saale, Werner Lehmann crashed severely and almost broke the car in two. Zimmermann rebuilt it in time for Round 2 on 20th May at Leipzig where the car finished in 2nd place, a feat Lehmann repeated at Dresden (Round 3) on 16th June. His two 2nd places out of four races made Championship leader Lehmann virtually unassailable.

 

In the three months gap in the Championship between Rounds 3 and 4, Daniel Zimmermann returned to the car's driving seat for some non-Championship events. On 1st July he raced his powerful two stroke car in front of 1/3 million spectators at the international races at AVUS in Berlin. He finished 11th in his heat and 11th overall in the final but was the first East German F3 driver to finish. This was a great result against the likes of Pim Richardson, Ian Burgess, Eric Brandon and Toni Kreuzer driving Cooper Nortons, Keift JAPs and Scampolo BMWs. Some reports say that Stirling Moss was in the same race.

 

Daniel Zimmermann also drove his car at the non-Championship events at Stralsund (15th July) and at Schwerin (26th August) but the results are not known.

 

His own confidence and driving skills boosted, Zimmermann decided to drive at the final Round 4 of the East German F3 Championship on 29th September. As with the AVUS races, that at the Sachsenring was a mixed race including many West European drivers. Zimmermann finished 5th overall in the Final and was the first East German driver to finish.

 

The overall results were enough to crown Werner Lehmann the East German Formula 3 Champion and, thanks to his sole victory at the Sachsenring, Daniel Zimmermann had accrued enough points to rank equal 3rd in the same Championship! This must be one of the very few occasions where two drivers sharing the same car have each finished on the overall Championship podium.

 

But the financial cost, the time and the lack of attention to his family and his bread-and-butter business cost Zimmermann dearly. So he disposed of his car. The buyer may have been a man called Karl-Georg Reinhardt from Herzberg (Elster) because he is listed as driving a Zimmermann 'Eigenbau' (self-built) car in three Formula 3 races in 1952; Rostock on 20th April where he DNF'd, Halle-Saale on 8th June when he finished 9th and Schwerin on 22nd June when he Did Not Arrive (DNA).

 

And that's the end of this car's story...but...

• What happened to the Zimmermann car after its last public appearance on 8th June 1952?
• Can anybody add any extra details to this story?
• Are there any technical articles on this interesting little car?
• What photos exist (I have a few but all are small and blurred)?
• Precious little is known of the technical details of Zimmermann's 500cc twin cylinder two stroke engine. Has that survived somehow?

Edited by Sergio, 18 September 2013 - 16:33.

[bradbury west]

Is it just this car you are researching, or 2stroke race engines generally? You might find it helpful if the latter is the case to search TNF for links to the Guidobaldi car. Supercharged 2 stroke radial engine laid flat at the rear of a single seater just post war in the early 1950s. It came to nothing but has recently been restored I believe. It is one of those devices you look at and marvel at the time and effort, and logic....
Roger Lund

[Sergio]

Roger,

 

I have followed the two stroke engine development path back from those used in the most recent examples of Grand Prix motorcycle and thus I am concerned with what I will call 'mainstream' two stroke technology. Radials are interesting to me and I will certainly check the Guidobaldi car and its supercharged radial two stroke engine. Of course, because many cylinders share the same crankcase in a radial engine, crankcase compression is virtual zero and supercharging would be the only way of getting the mixture into the cylinders. I just love engine technology but for reasons of space and the need for forced induction (more to go wrong) radial two-strokes never really took off (to coin a phrase).

 

And sadly, radials don't play a part along the main artery connecting the most recent Japanese two strokes with the two stroke developments (mainly in East Germany) in the years following World War Two. For example Zimmermann's unique rotary disc valve of 1949 was a seminal idea that led directly - via IFA/MZ (who first picked it up in the spring of 1953 when Walter Kaaden copied Zimmermann's design) - to the implementations of Suzuki/ Yamaha/ Kawasaki/ Honda et al of the 1960-1980 period.

 

Zimmermann's F3 500cc twin cylinder engine, designed in 1949 and built and first ran at Dessau in October 1950, was the first engine he ever designed and the first ever fitted with this type of valve. I'd like to know how he built it into his twin cylinder engine. Not very easy with a primary drive to consider unless it used the Trabant's internal disc valve system.

 

Zimmermann's valve was unique in that it was thin (about 0.5mm thick) and ran inside its own housing outside of the crankcase. Pervious two stroke rotary disc valves were thick (think 5-6mm) and were located inside of the crankcase where the space they occupied served to reduce the primary compression ratio. The first engine of which I am aware that used this implementation originated in Britain around 100 years ago and was first raced in the early 1920s. A similar valve appeared at about the same time in Germany.

 

It's interesting that model aircraft and radio controlled car people still talk of the 'Zimmermann Valve' when referring to a rotary disc valve outside of the crankcase of their miniature engines. Elsewhere, Zimmermann's name is rarely linked with the rotary disc valve. Indeed if any name is connected to this line of development it is sadly that of Walter Kaaden.

[Allan Lupton]

Previous two stroke rotary disc valves were thick (think 5-6mm) and were located inside of the crankcase where the space they occupied served to reduce the primary compression ratio.
 
It's interesting that model aircraft and radio controlled car people still talk of the 'Zimmermann Valve' when referring to a rotary disc valve outside of the crankcase of their miniature engines.

The addition of anything that helps fill the crankcase reduces the primary clearance volume so increases compression ratio. However I would expect the crankcase has to be made bigger somewhere to accommodate the valve so there'd be no nett change as the space occupied by the valve would not otherwise be there.

When I had such things (1950s)a number of model aeroplane engines worked on the modified Day cycle with rotary valves, either using a part-hollow crankshaft or the simple disc valve. Can't say when those designs originated but they were not new.

[Michael Ferner]

The addition of anything that helps fill the crankcase reduces the primary clearance volume so increases compression ratio.

 

Are you sure?

[Sergio]

The addition of anything that helps fill the crankcase reduces the primary clearance volume so increases compression ratio. However I would expect the crankcase has to be made bigger somewhere to accommodate the valve so there'd be no nett change as the space occupied by the valve would not otherwise be there.

When I had such things (1950s)a number of model aeroplane engines worked on the modified Day cycle with rotary valves, either using a part-hollow crankshaft or the simple disc valve. Can't say when those designs originated but they were not new.

Of course, Allan, you are right in principle but that's ignoring the additional radial and lateral clearance needed around the thick disc and moreover, the volume of the chunk removed from the disk that allows the valve to work. All of these serve to increase the 'dead' volume of the crankcase and thereby reduce its pumping efficiency.

[Allan Lupton]

The addition of anything that helps fill the crankcase reduces the primary clearance volume so increases compression ratio..

Are you sure?

Yes.

Compression ratio is the ratio of (clearance volume)/(swept volume + clearance volume) and in this case (primary CR in a Day cycle two-stroke) most of the clearance volume is that part of the crankcase not filled with crankshaft and conrod parts.

 

ETA Sergio's post appeared while I was preparing the above.

I'd just say that clearances round the disc can be, or even have to be minimal. For it to work it must seal against the static end of the crankcase (zero clearance) and as that means no end float it can be as close to the bigend as you like. It needs a good bearing so radial clearance can be tiny. I agree the cut-out volume is inescapable, but 5mm isn't that thick on a 250cc size unit.

 

ETA I've tried three times to start with "Allan Lupton, on 19 Sept 2013 - 23:27, said" above the quote from my post and the system won't have it, whereas the old one would.

AAAArrgh

Edited by Allan Lupton, 20 September 2013 - 07:27.

[Sergio]

Allan,

If you took an engine with a given primary CR and then enlarged the internal volume at one side and COMPLETELY filled it up with a disc valve, the primary CR would remain unchanged and you would be correct. But the valve wouldn't work because it would probably seize up and if it didn't, there would be no slot through which the incoming charge can enter the crankcase. As I have explained, you cannot completely fill up the extra volume because the disc valve needs running clearances and a 'slice' taken out of it for it to work. Ergo, the crankcase compression will be reduced.

 

Here's an example of an early internal disc valve...

 

 

This early French design is particularly inefficient but it makes the point. You will also see that to avoid the incoming charge being blanked by the crankshaft cheek (full circle flywheels for maximum CR), the designer has actually put a corresponding slot in the flywheel lowering the primary CR even more.

 

But then, engine designers in those days were really two stroke pioneers. They didn't really understand the two stroke principals almost 100 years ago.

 

And that's the brilliance of Daniel Zimmermann; he did understand how they worked and his DNA can be found in all modern disc valve racing two stroke engines since WW2.

Edited by Sergio, 20 September 2013 - 07:59.

[Allan Lupton]

Ah, yes if you apply a disc valve to that arrangement it is difficult to get good gas-flow.

Prejudiced by the model aeroplane engines I had, I'd assumed an overhung crank with the valve being all there was to the right of the bigend apart from a crankpin extension to drive it.

Never did like Day cycle - the duplex type as in Trojan (or Trossi Monaco) and the Oechselhauser as in 1925 GP Fiat are much sounder engineering in my opinion.

[Michael Ferner]

All right, I'm the first person to confess that I do not know a lot about two-stroke engines!

 

 

But then, engine designers in those days were really two stroke pioneers. They didn't really understand the two stroke principals almost 100 years ago

 

 

I can see that I am in good company here (even if "outdistanced" by a 100 years ;)), as I needed to read up on primary CR for two-strokes to really understand what you guys are talking about. I will now sit back (stand in the corner?) to merely listen to this fascinating discussion.

[T54]

Disc-valve induction offered a much better timing control than more erratic piston porting, and before reed-valve technology and electronically controlled rotary exhaust valves became standard, a 2-stroke engine fitted with properly timed disc valve had a huge power advantage over pretty much anything 2 or 4 strokes, as long as the exhaust part of it was also understood. The so-called expansion chamber engineered by mostly German 2-stroke experts (both east and west), then in Japan (especially by Yamaha which had an edge over the German technology brought by Ernst Degner to Suzuki), made the disc-valve engines to work and produce the first 400 HP per liter ever in non supercharged engines.

By 1981, a 50cc Kreidler GP engine with single disc valve and a 28 mm carburetor pushed 22.5 HP and those tiny motorcycles exceeded 120 MPH, while being limited by regulations to only 6 speed gearboxes, but still providing a very adequate torque on a fairly wide curve.
Then reeds came, first from model-airplane engines, then from motocross engine technology and today, one of the all-time greats in 2-stroke engine designs, a man associated with some of the most successful GP motorcycles ever built, reckon that they got 53.5 HP from their 125cc Aprilia and think that it the GP powers that be had not killed the 50cc class, 33 HP would have been the norm while providing much greater flexibility.

While I cannot help Ray in his quest for the F3 car he is looking for (if it still exists...), I can say that having driven several of these small displacement (50 and 125) GP bikes in competition provided astounding results even if many years ago. My lap time with a 125cc Italian-built Morbidelli at the former Riverside Raceway equalled the FTD established in a club event with my pretty damned fast 270 HP Porsche RS on hand-cu slicks on the same track a few years later in pretty much the same conditions... giving you an idea of how efficient these tiny machines truly were.

 

[wolf sun]

According to this website (of which you are probably well aware), the Zimmermann Formula 3 was destroyed in a crash.

 

http://www.classic-m...index-teil1.htm

[FrankCornell]

500cc racing in Germany (1948-50) is very briefly covered in "500cc Racing" by Gregor Grant, (p142-43) but without mention of Zimmermann.

[wolf sun]

It seems that Zimmermann was 'bought out' by IFA - in the process becoming responsible for the construction of racing boat engines in East Germany.