RATED AT 1,000-1,050 HORSE-POWER, the DB 600 petrol engine is installed in many of Germany’s fastest aeroplanes. It is a twelve-cylinder inverted V liquid-cooled engines, in two blocks of six, with a capacity of 33·9 litres. There are two types - the A/B, with a sea-level supercharger, and the G/H, supercharged to about 13,000 feet. One of these engines was installed in a single-seater Heinkel aeroplane, which flew 100 kilometres (62 miles) in May 1938 at 394 miles an hour.
THE Mercedes-Benz diesel and petrol engines, manufactured by the Daimler-Benz Aktiengesellschaft, are notable examples of modern high-power engines. Two models, the 1,200 horse-power DB 602 diesel and the petrol engine DB 600, rated at 950-1,000 horse-power, are especially esteemed. DB 602 engines are being installed in the new Zeppelin airship LZ 130. The petrol engine is fitted to a number of Germany’s newest and fastest aeroplanes.
The performances of these two aero engines have a special interest because the engines are in a direct line of evolution from the motors of cars produced by Gottlieb Daimler and Karl Benz. The name Mercedes-Benz continues in the air the reputation for progress and speed that the Mercedes and Benz motor cars established during the infancy of the internal combustion engine. Originally the two companies, founded respectively by Daimler and by Benz, were separate. They both made aero engines before 1926, when the two companies combined.
Selection of the DB 602 diesel engine for the new Zeppelin airship indicates the reliability of this sixteen-cylinder water-cooled V type engine. The design was evolved for the Hindenburg, the LZ 129, in which four engines were used. The steel cylinders of the DB 602 engine have Daimler-Benz precombustion chambers. The connecting rods have roller-bearing big ends and the crankshaft runs in nine bearings with hardened bearing surfaces. There are two inlet valves and two exhaust valves to each cylinder. The rocker-boxes and push-rods are enclosed. To give direct reversing, the camshafts are moved by compressed air. Reduction gear is fitted so that the propeller speed is different from engine speed. Fuel is injected by four fourfold Bosch fuel pumps, driven off the front end of the crankshaft. A governor enables the engine to idle at slow speeds on sixteen or on eight cylinders. The lubrication system has two scavenge pumps. The main pressure pump draws oil from the tank and feeds a number of piston-pumps, each of which lubricates a main bearing.
Starting is by compressed air, the compressor being of the two-stage declutch-able type. To assist starting in cold weather, the cooling water and the oil can be circulated through a heater. Fuel consumption over cruising range up to 900 horse-power is 0·37 lb per horse-power-hour; at the maximum output of 1,200 horse-power it is 0·39 lb per horse-power-hour.
The four engines installed in the Hindenburg gave that airship a cruising speed of seventy-eight miles an hour and a maximum speed of over eighty-four miles an hour. The fact that the same model of engine is being used in the new airship shows how well this engine fulfils exacting requirements.
The DB 600 petrol engine was produced in the summer of 1937 and attracted great attention because of the performances of the aeroplanes in which it was fitted. It was first seen in Great Britain when General der Flieger Staatssekretar Milch, Germany’s Secretary of State for Air, accompanied by other senior officers, arrived in October 1937 in a special Heinkel He. III. This machine was powered by a pair of the new engines. One of the new engines powered the Messerschmitt Bf 109 single-seat fighter with which Dr. Wurster set up at Augsburg, Germany, on November 11, 1937, a speed record for landplanes of 379 miles an hour. In May 1938 a single-seat Heinkel machine, fitted with a similar engine, flew 100 kilometres (62 miles) at 394 miles an hour.
The twelve-cylinder inverted V liquid-cooled engine is made in two types, the A/B model, which has a sea-level supercharger, and the G/H model, which is supercharged to about 13,000 feet. The bore is 150 mm., the stroke 160 mm. and the capacity 33·9 litres. The approximate dimensions are length 68 in, breadth 28 in and height 39 in.
The A/B is rated at 1,000 horsepower for the take-off, at 910 horsepower at sea level at 2,400 rpm, and at 800 horse-power at 2,200 rpm. The G/H is rated at 1,050 horse-power for the take-off, at 800 horse-power at 2,300 rpm at approximately 13,000 feet, and at 1,050 horse-power at 2,400 rpm at the same altitude. The fuel consumption at cruising speed is 0·496 lb per horse-power-hour.
The twelve cylinders are in two blocks of six. The compression ratio is 6·5 to 1. There are two connecting rods to each crankpin; one runs on roller bearings on the crankpin, and the other on plain bearings on the first rod. The crankcase is strengthened internally with longitudinal and transverse ribbing. Five transverse walls carry the main bearings for the crankshaft, which is forged in one piece, and runs in seven steel-backed lead-bronze bearings. At the front end of the crankshaft is a key for the pinion of the reduction gear, which is a spur-gear with alternative reduction ratios of 1·55 to 1 or 1·88 to 1. All accessories are driven from the rear end of the crankshaft. There are two inlet and two exhaust valves to each cylinder operated by separate camshaft for either bank. Carburation is by pressure carburettor on the braked-air principle between the cylinder banks.
Two Bosch twelve-cylinder magnetos supply the current for ignition and there are two sparking plugs in each cylinder. The magnetos are screened to prevent interference with the radio. Bosch electric or hand inertia starter is provided. Lubrication is by one pressure pump and two scavenge pumps.
The single-stage centrifugal supercharger is fitted to one side at the back of the engine, with boost control for the high flying model. The unusual position enables air to be taken in through the fuselage nose side as easily as through the leading edge of a wing.
SELECTED FOR THE ZEPPELIN AIRSHIP LZ 130, the DB 602 is a sixteen-cylinder V type diesel engine. The steel cylinders have Daimler-Benz precombustion chambers. The connecting rods have roller-bearing big ends and the crankshaft runs in nine bearings. There are two inlet valves and two exhaust valves to each cylinder. Four engines of this type were fitted in the Hindenburg and gave that airship a cruising speed of 78 miles an hour and a maximum speed of over 84 miles an hour.