primotipo…

When I think of the pioneers of mid-engined racing cars, it’s always the Auto Unions of the thirties which pop most readily into my mind, but that does the 1923 Benz Tropfenwagen a huge disservice.

Dr Edmund Rumpler’s ‘Tropfenwagen’ (teardrop vehicle) was the hit of the 1921 Berlin Motor Show, it was said to resemble a Zeppelin Airship. Rumpler’s aeronautical design in particular and automotive experience went back to 1903, click here for more and Rumpler and the significance of this design; http://8w.forix.com/rear-engines-prewar.html

 

The car had low drag coefficient of 0.28, a rear engined layout and independent suspension. Benz’ Berlin representative and future Auto Union Team Manager Willy Walb could see the potential of the design concepts when applied to a racing car. ‘Benz obtained the reproduction rights for this car immediately’ according to Mercedes Benz. In 1922 Chief Engineer Hans Nibel led a team which designed and developed the Benz ‘Type RH’.

The chassis was of the period typical ladder frame type, it was ‘underslung’ resulting in the racers low build.  Nibel specified a six-cylinder, two litre, DOHC, 12 valve motor of 1991cc, fed by two Zenith carburetors the unsupercharged motor gave about 90 bhp @ 5,000 rpm. The Benz had a three speed gearbox behind the engine with a diff which was attached to the frame, short halfshafts with universal joints provided the drive to the rear wheels. Leonard Setright accords the car the honour of having the first independent rear suspension of any racing car. Brakes were inboard at the rear, outboard at the front with supreme streamlining of course- the machine had a rounded nose, a tapering tail and a radiator which sat proud of the rear bodywork, aft of the driver mimicking some early seventies F1 airboxes.

 

Whilst four cars were commenced in 1922 they were not completed until the following year ‘due to the economical situation at the time’ Mercedes wrote. Finally ready, the design only contested one major race, the 9 September 1923 Grand Prix of Europe at Monza, attended by the most enormous crowd.

Drivers were Willy Walb, Franz Horner and Fernando Minoia. The pace up front was set by the Fiats and Millers but the unconventional cars finished fourth and fifth- Minoia from Horner but both were 4 laps adrift of the winners. Walb’s machine had engine troubles.

The race was won by Carlo Salamano from Felice Nazzaro in Fiat 805s powered by Tipo 405 eight cylinder, supercharged, DOHC, two-valve, 2 litre motors- the winner covered the 80 laps of the 6.214 mile course in 5 hours 27 minutes 38.4 seconds. Jimmy Murphy was third in a Miller 122, over 5 minutes adrift of the victor, then came Minoia, Horner and Martin de Alsaga in another Miller.

It was an important race for the supercharged 146 bhp Fiat 405s given their French GP failures at Tours earlier in the year- the cars placed first and second establishing the dominance of supercharged engines in the sport until Ferrari challenged the orthodoxy with their 4.5 litre V12 normally aspirated 375 in 1951.

The five hour race was not an exciting one. The 120 bhp Miller straight eight, normally aspirated, DOHC, two-valve 122s were nowhere near as quick as the Fiats and the Benz’s were further back again, nonetheless to have two of the three new cars entered finish the long race was a portent of greater performance in the future with development.

 

 

The cars were evolved, but not in the most critical manner. The rear brake drums changed from inboard into a more conventional location within the wheel hubs, the cars were also fitted ‘with a new dropped rigid steering stub axle instead of the straight front axle’- the translation from German to English seems to have suffered here!- i’ve no idea what that means. Most importantly, a supercharger was not fitted…

From 1923 a sports version was built which also competed in races and trials as well as the GP machines, but as dly, post Monza 1923 the cars were deployed in minor events only.

Horner was fifth in a hillclimb at Solitude in 1924, Walb won others at Konigstuhl and Freiberg in 1925. Future Mercedes works driver Rosenberger was quickest at Herkules. The car also did well in races held to open Opel’s new test track, Tigler won a ten lap event.

Rosenberger’s winning run in the Rund um die Solitude on May 16 1925 was the cars last run ‘in period’, at which point the company returned to building conventional cars. It’s worth noting that Benz & Cie and Daimler Motoren Gesellschaft formally merged after two years of cooperation into Daimler-Benz on 28 June 1926, their joint automotive products called Mercedes-Benz.

Ferdinand Porsche was appointed Technical Director of Daimler in 1923, there is little doubt he took a long hard look at the Tropfenwagen design and used some of its concepts in his later Auto Unions.

Etcetera…

 

What an enormous crowd.

That is a Miller 122 amongst the masses in the foreground- three of them were entered and driven by Murphy, Martin de Alsaga and Louis Zborowski.

Benz up the road a bit surrounded by another big crowd.

Such a distinctive shape for the time- it is a shame that the machines were not supercharged which would have gone most of the way to bridging the gap to the dominant Fiats of the day- click here for a piece on those epochal Fiats; https://primotipo.com/2019/11/22/fiat-806-gp-1927/

Overhead shot shows the location of major components, the 130 litre fuel tank up front must have given the crews pause for thought.

Inline six, three speed gearbox and differential behind it and swing axle rear suspension, 4.53 metres long, 1.58 metres wide, wheelbase 2.78 metres and a quoted weight of 750 kg.

 

That is the radiator mounted forward and above the rear wheels.

Ignore that though and take in the ‘pure tear-drop’ shape as it tapers from front to rear.

Great rear suspension detail- swing axles, notice the inner pivots alongside the diff and leaf springs which are performing locational duties and are inwardly inclined where they bolt at their inner ends to the engine. Note too the curvy radiator overhead.

The originality of the thing takes your breath away really.

 

Carefully posed shot at Monza with probably the three drivers and two of the technicians- perhaps Franz Horner at left then Fernando Minoia on the other side of the car and in front Willy Walb.

Induction side of the engine with the two Zenith carbs prominent- note the inner spring mount under the carb closest to us.

The six cylinder, gear driven DOHC, two valve Type ‘Bz 6516’ engine is of built up construction- steel cylinders with welded on steel water jackets, the cylinder head is fixed, welded to the cylinders.The crankshaft is Hirth type and has seven main, roller bearings. Notice how the front section of the crankcase spans the chassis longitudinal members.

The bore and stroke are 65 x 100 mm, 1997 cc, one spark plug per cylinder, Bosch magneto ignition, compression ratio 5.8:1. Maximum power 90 bhp @ 5000 rpm with a maximum rev limit of 5,400 rpm.

 

 

Exhaust side of the engine.

 

Minoia on the inside of two Fiat 805 on the first lap of the Monza race.

And below in the pits, note the additional small radiator alongside the driver, which is shown more clearly in the final photograph in this piece below.

 

Steering is worm and nut, front suspension by rigid axle, leaf springs and friction shock absorbers. Wire wheels of course, 105 cm in diameter with mechanically operated drum brakes all around, initially inboard at the rear.

Bibliography…

‘The GP Benz Tropfenwagen’ Bill Boddy in September 1986 MotorSport, ‘Benz Tropfenwagen’ in grandprixhistory.org, Mercedes Benz public archive, ‘The Grand Prix Car’ Leonard Setright

Credits…

Brian Hatton, Popperfoto, GP Library, Mercedes Benz AG, Agence de presse Meurisse

Tailpiece: Fernando Minoia, Monza 1923…

Finito…