The American R-3550 and the Soviet ASh-73TK were both large, twin-row engines with nine cylinders in each row. While both engines had an identical bore size of 155.6 mm, the ASh-73TK had a longer stroke size of 169.9 mm and a larger displacement of 58.122 liters. In contrast, the R-3550 had a stroke size of 160.2 mm and a displacement of 54.86 liters.
The ASh-73TK was developed from the initial ASH-73, which was a “cousin” of the Wright R-3350, having evolved independently from the Wright R-1820 Cyclone engine but using similar design elements. However, it was modified with the addition of twin TK-19 exhaust-driven two-speed superchargers and a single-speed geared centrifugal supercharger in order to improve high-altitude performance. The turbochargers, carburetors, and bearings of the ASh-73TK were copied from the R-3550.
Due to its similarities to the R-3550, the ASh-73TK was chosen for use in Soviet copies of the B-29 (the Tu-4), allowing it to be fitted into the copies of B-29’s cowlings and nacelles.
While ultimately reliable, the ASh-73TK did encounter some induction system fires during its early stages of use, similar to the issues faced by the R-3550.
We can compare the parameters of both engines in the following table:
|Manufacturer||Wright Aeronautical Division of the Curtiss-Wright Company||OKB-19, later the Perm Motor Design Bureau|
|Applications||B-29, A-1, DC-7, P-2, Lockheed Constellation||Tu-4, Be-6, Tu-75, Tu-80, and S-82(Not completed)|
|Type||18 cylinders, 2-row radial, air-cooled, geared drive, Supercharged, 4-cycle||18-cylinder two-row star-shaped, air-cooled, geared, with one-stage single-speed monitoring station;|
|Supercharger||G.E. Gear-driven, 2-speed supercharger, ratio 6.61:1 and 8.81:1||2 x TK-19 exhaust-driven turbo-chargers and a second supercharging stage, with PTsN single-speed centrifugal blowers driven by the engines.|
|Bore||6.125 in.||155 mm||6.125 in.||155.6 mm|
|Stroke||6.3125 in.||160 mm||6.689 in||169.9 mm|
|Displacement||3.347cuin||54,9 lit||3.546.8 cu in||58.122 liters|
|Diameter||55.8 in.||1417 mm||54.13 in||1375 mm|
|Length||55.8 in.||1935 mm||90.16 in||2290 mm|
|Weight||2670 lb.||1211 kg||2952 lb||1339 kg|
|Fuel consumption (cr)||0.46 lb./h.p./hr.||210 g/hp/hr||0.69-0.74 lb/hp-hr||315-335 g/hp-hr|
|Rating (take off)||2,200 h.p./2,800 r.p.m. at sea level||2,400 hp|
|Rating (normal)||2,000 h.p./2,400 r.p.m./4,500 ft. (1 400 m)||2,000 hp (2,400 rpm, 28,215-30,515 ft or 8,600-9,300 m)|
|Military||2,200hpr2,600rpm/25,000ft (for maximum of 5 minutes)||2,200 hp (26,250-28,545 ft or 8,000-8,700m)|
- Wright R-3350 Duplex Cyclone technical specification
- Shvetsov ASh-73 Engine
- Tupolev Tu-4 Standard Specification & Performance
- Boeing B-29 Superfortress Facts: 11 things to know
- Tupolev Tu-4: The First Soviet Strategic Bomber by Yefim Gordon and Dmitriy Komissarov
- Russian Piston Aero Engines: The Complete Story by Victor Kotelnikov
- Boeing B-29 Superfortress: The Ultimate Look: From Drawing Board to VJ-Day by William Wolf