Mercedes-Benz Model DB-601

By Paul H Wilkinson,
Consultant, Diesel Aviation

One of Germany's most popular engines is the Mercedes Benz. which powers many oi the Heinkel and Messerschmitt combat planes used by the Nazi air force

The Mercedes-Benz DB 601 aircraft engine, built by the firm of Daimler-Benz AG in its huge factories at Stuttgart-Unterturkheim and elsewhere in Germany, is perhaps the best known military engine in Continental Europe. Undoubtedly, it has seen the most active service as it has been used extensively in large numbers of Heinkel He-111 bombers and Messerschmitt Me-109 fighters since the first days of the European War. It is also used extensively in Dornier Do11 and Do-215 bombers, and in Heinkel He-112 interceptors and Messerschmitt Me-110 convoy-fighters or destroyers. When production figures are released it would not be surprising to learn that at least 100,000 of these engines were produced during the years 1939 and 1940.

The DB-601 was developed from the DB-600 engine of similar design which was introduced in 1937 to meet the demand for a high-performance military engine. Low weight and economical fuel consumption, together with maximum reliability, were stressed as essential requirements. The overall dimensions of the engine have been kept as small as possible to reduce head resistance and its exterior cleanness simplifies the cowling problem to a great extent. The inverted cylinder construction and cantilever method of suspension in the airframe permit interchangeability between both models of the Mercedes-Benz engine and the Junkers Jumo 211 engine, which is of almost identical size and power output.

The earlier Mercedes-Benz DB-600 was rated at 1,050 hp at 2,400 rpm for takeoff and also developed this power at an altitude of 13,100 ft. It was equipped with a pressure carburetor between the supercharger and the intake manifolds and an automatic timing device which permitted a 10 percent overload for a period of one minute. Using 87-octane gasoline, four of these engines installed in a Junkers Ju-90 airliner established a World's Record by carrying a payload of 10,000 kg (22,050 lb) to an altitude of 7,242 m (23,750 ft.) on June 8, 1938 in Germany.

The latest model DB-601 engine is rated at 1,200 hp for one minute for takeoff and develops this power at an altitude of 16,400 ft. At 25,000 ft, its power output is approximately 850 hp. It weighs 1,265 lb, or 1.05 lb per hp. It runs on 87-octane gasoline and is equipped with direct fuel injection whereby its consumption at cruising speed does not exceed 0.45 lb per hp per hour. This model has the World's Speed Record of 468.9 mph to its credit, established in a Messerschmitt Me-109 fighter on April 26, 1939.

With regard to construction details, the crankcase and the two cylinder blocks of the DB 601 are a one-piece casting of Silumin-Gamma alloy with an angle of 60° between the two inverted blocks. The casting is braced by means of five transverse partitions as well as by interior longitudinal and transverse ribs. The steel cylinder barrels are screwed into the cylinder blocks. Each cylinder has two inlet valves and two exhaust valves actuated through the medium of steel lingers by an overhead camshaft along each block. All of the valves have hollow heads and stems and the exhaust valves are sodium-cooled.

The crankshaft is of six-throw design and is machined from a one-piece steel forging with counterbalances. It is supported in seven steel-backed lead-bronze bearings. Each pair of connecting rods functioning on the same throw consists of a plain rod containing a roller bearing in its big end and a forked rod attached to the plain rod by means of plain bearings. The pistons are made of aluminum alloy and are fitted with pins of the floating type.

The supercharger is mounted in a similar manner to the supercharger on the Junkers Jumo 211 engine in that it is gear-driven from a transverse shaft at right angles to the axis of the crankshaft. This arrangement permits full advantage to be taken of the high velocity air stream emanating from the periphery of the closed-type, high-speed impeller. On the DB-600 and DB-601 engines, the supercharger is of one-speed, one-stage construction with screened air intakes in its sides. It is fitted with an automatic boost control and charging pressure governor which maintains a constant pressure in the intake manifolds of the engine until its rated altitude is reached.

Direct fuel injection into the cylinders of the engine is provided by means of a twelve-unit high-pressure pump mounted between the cylinder blocks where it is fed by a Graetzin transfer pump. The high-pressure leads between the pump and the cylinders are of equal length. The ignition system comprises two twelve-cylinder magnetos of Bosch manufacture together with shielded plugs and wiring. The mounting of the magnetos is unusual in that they are attached to a small accessory gear box on top of the rear portion of the crankcase where they and other accessories, such as high-pressure and low-pressure pumps, so mounted can be removed en bloc for servicing.

The lubrication system functions on the dry-sump principle with one pressure feed and two scavenge pumps of the rotary-gear type to circulate the oil through the engine and via a small radiator on top of the crankcase, back to the service tank. The used oil collects by gravity in the oil-tight valve covers whence it is removed by the scavenge pumps. The pressure used for the main bearings is 45 lb per sq in.

The propeller shaft is hollow to permit firing a shell gun through it and is driven through spur gears having a reduction ratio of 1.55 to 1 or 1.88 to 1. The shell gun is attached to a flange at the rear of the engine with four studs and nuts. The propeller shaft flange is provided with 8 holes and 96 serrations, which is standard practice in Germany.

The engine is started by means of a Bosch hand or electric inertia starter flange-mounted on the crankcase where it engages with the rear end of the crankshaft. Water is used for cooling purposes and is circulated by a centrifugal pump in a closed-circuit system. Ethylene glycol is not regarded with favor on account of the servicing complications involved.

Everything of the Mercedes-Benz DB-600 and DB-601 engines has been designed with a view to relieving the strain on the pilot. Apart from the throttle, all of the controls are automatic. The interchangeability which exists between these engines and the Junkers Jumo 211 places the German Luftwaffe in a very strong position for maintaining its warplanes in the field.

Specifications
Mercedes-Benz DB 601 aircraft engine
Type:   twelve cylinders,
   water cooled,
60° inverted vee,
geared drive,
four cycle
Bore and stroke   5.90 x 6.30 in
Displacement   2,070 cu in
Length and area   68 in x 6.2 sq ft
Rated output   1,200 hp at 16,400 ft
   1,200 hp for takeoff
Total weight (dry)   1,265 lb
Specific weight   1.05 lb/hp
Fuel consumption   0.45 lb/hp/hr
Oil consumption   0.018 lb/hp/hr
Compression ratio   6.8 : 1
This article was originally published in the October, 1940, issue of Aviation magazine, vol 39, no 10, pp 61, 94.
The original article includes a photo with two views of the engine: head-on and ¾ right-rear.