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:
| Model | R-3550 | ASh-73TK | ||
|---|---|---|---|---|
| Manufacturer | Wright Aeronautical Division of the Curtiss-Wright Company | OKB-19, later the Perm Motor Design Bureau | ||
| Production run | 1941-1945 | 1947-1953 | ||
| Produced | 32,221 | 14,310 | ||
| 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 |
| Compression Ratio | 6.85:1 | 6,85:1 | 6.9:1 | 6.9:1 |
| 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) | ||
Further reading
- 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
Source
- 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
