The Grade F1 was a low-volume German small car developed by aero-engineer Has Grade. The little car had number of unusual design features and was advanced for its time, however, it also had its problems. A small handful of cars were built between 1921 and 1927, when Grade went out of business. Many years later, in the 1950s when East German designers were keenly focused on developing a simple, small car for the people, Siegfried Rauch wrote his reminiscences of owning two Grade's during the prewar period.
The Little Grade
By Senior Engineer Siegfried Rauch
"If you don't buy the little Grade today, then you have lost a day - because you will definitely buy it tomorrow!" This is how the prospectus of the small car began (it may have been around 1924), which the well-known aircraft designer, the pioneer of the small two-stroke aircraft engine, Hans Grade, built in Bork on der Mark. As original as the advertising slogan was, the whole little car was just as original. Unusual in its structural design and the external shape and something completely different from all the many small car designs that appeared on the market at that time (only to disappear again just as soon). The Grade was not simply a cranesbill-like reduction in size of a "real" automobile, but a functional design that, of course, could not deny the paternity of the aircraft manufacturer.
Today especially, when the call for a small car is so urgent in our country, when large motorcycle factories such as BMW in Munich consider the problem of the small vehicle to be so urgent that they would rather become a licensee of the Italian Isetta than undertake their own construction and development project, or where, as with NSU, their entire racing program is cancelled in order to concentrate all constructive energies on the development of the smallest vehicle for the broadest mass. At this time, we should probably remember a construction that a technician who was far ahead of his time created 30 years ago. Then as now, the small class wanted less to compete with the big automobile than to capture the current and future motorcyclists who are looking for a multi-track, dirt and weather-proof vehicle. Even though the small Grade was built 30 years ago, even though it has been dead for a long, long time – the idea, the longing for a real small car lives on - it is still a problem that has not been solved and hundreds of thousands of people around the world are still waiting for that!
The little Gradewagen's engine was an air-cooled two-cylinder, two-stroke, with a turbo-fan (a rather bold expression for a flimsy fan in a primitive tin casing!). With a 70 mm bore and 105 mm stroke, i.e., a stroke (bore ratio) that is completely impossible for a two-stroke engine today, it was about 800 ccm and delivered about 16 hp at 1600 rpm. Lubrication was carried out by a valveless pump and ignition by a Bosch magnet. The intake control was not, as is usual, the lower edge of the piston - instead, spring-loaded plate valves were arranged in the two overflow ports of the cylinder; which (as so-called "snifting valves") open when the piston rises under the effect of the vacuum created in the housing and lets the fresh gas flow in. The whole intake story was a bit daring - a monster carburettor supplied the mixture - but the throttle valve was strangely enough, not between the carburettor and the cylinders, but with two small flaps, which were arranged on a common shaft, the overflow cross-section was controlled just before the overflow slots. At the time, I owned two such little cars in quick succession - there was a lot of trouble with them - but arguably most of the hassle was with those automatic valves and the carburettor, which was a real science to get right!
The crankshaft ran in plain bearings, which also had to seal the shaft passages in the housing. The connecting rod bearing was particularly unusual - the connecting rod feet were undivided, the connecting rod bearings represented a divided bronze bush with an external thread. During assembly, the big end was threaded over the narrow crank webs, and then the threaded bush was screwed in and secured by caulking. You can probably imagine what it looked like with correct bearing clearance!
That's him! From the front as well as from below it stands out like a somewhat bulky boat on wheels. Left (in front) the motor, in the middle of the car the shaft and behind (right) the friction gear.
Incidentally, the extraordinarily long and heavy cast iron pistons did not have a deflection nose, but a simple vertical deflection plate - that the heat could be dissipated at all still amazes me to this day.
A fairly heavy shaft led from the engine (without the interposition of any joints!) through a pipe to the gear compartment behind the seats. The pipe could be shifted and turned by means of a driver device.
In the gearbox was a friction gear - a really great thing! Two gigantic, heavy pulleys at right angles to each other, which could be pressed against each other or removed from each other by means of a hand lever via a cable pull (the latter operation also by means of a foot pedal, if you wanted to disengage the clutch!). The disc on the transverse countershaft had a friction lining on its circumference and could be moved, again using a hand lever and cable pull. As a result, different disc radii came into contact with each other - and the ideal continuously variable transmission was achieved. An open-running roller chain led from the countershaft to the right rear wheel - on this side only was the brake drum, the left rear wheel was simply wedged onto the continuous rigid rear axle. The second brake sat as a band brake on the countershaft in the gear compartment, when the countershaft (when disengaging) was pushed back far enough, this second brake automatically came into operation.
In Operation
If the clutch was allowed to slip for too long, a small area was worked off the friction lining - and the large number of areas that developed over time then resulted in a rumbling and roaring in the rear of the body that was almost unbearable.
The most original thing about the whole vehicle, however, was the chassis: today there is a lot of talk about a self-supporting body and a monocoque construction - Grade already had both 30 years ago. The whole car consisted of a sheet metal tub, from which the four quarter-elliptic springs protruded at the front and rear, which again ended or were screwed into shoes, which were welded to the axles. The springs themselves, constantly lubricated in this way, sat in leather sleeves, so that apart from the wheel bearings and the steering knuckles there were no maintenance points on the entire chassis. Over the lower tub a body hood made of thin sheet metal was put on. Where the two halves sat on top of each other, the raised "footboard" or the fenders were attached. Was there constructive momentum behind it or not? A suggestion - without saying that we can now after 30 years, adopt these things unchanged?
The front wheels, which were also attached to the rigid tubular axle, were steered using a triple chain and fivefold steel cables - based on aircraft construction, which didn't really appeal to the public at the time, but in my opinion never led to any complaints. Front axle, steering knuckle carrier, steering knuckle, etc., everything was welded together from thin-walled tubular steel.
The front part of the body was also a muffler; the bonnet consisted of two halves, the upper flange of which was held together by a slotted tube to be pushed over it. The steering wheel could be adjusted without tools using a simple clamping device. The cellon windscreen could be removed with a flick of the wrist, and the convertible top could be folded over the car from the driver's seat (very practical, but anything but elegant!).
A multitude of such small, nice ideas made the little Grade appear to me as the goal of my desires for years and, as I said, I had two of the little fellows for a while. The fact that I later returned to a motorcycle with regret was typical of the fate of the Gradewagen in general. It was probably too far ahead of its time. The technology of vehicle construction did not yet keep pace with the flight of ideas of its designer, but when I look up the old pictures again today, which show the small Grade, in the Brandenburg sand, in the Austrian Alps, in medieval Bavarian towns and on the concrete of the Berlin cycle track - then I have to say that it's a shame about fate of this truly original construction. Perhaps some of its details should be taken up again today with modern means?
Original published in Der Deutschen Strassen January 1955:
https://dkwautounionproject.blogspot.com/2023/04/der-deutsche-strassen-verkehr-january.html
When we attended Schloss Schwetizingen motor festival in 2016 we saw one of the few surviving Grade cars. It is fully restored and running.
No comments:
Post a Comment