Radial vs radial

Discussion in 'Aviation' started by rogerwilko, Jan 6, 2015.

  1. rogerwilko

    rogerwilko Member

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    Any advantages with the Wright cyclone 1820 over Pratt Whitney 1830? Seems the 1830 would be more complicated and expensive for similar horsepower.
     
  2. tomo pauk

    tomo pauk Creator of Interesting Threads

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    I'd say that it depends what application of a particular engine it is. If one want's a smallish well streamlined fighter, where the smaller frontal area matters, then better use the R-1830.
    If the application is a multi-engined aircraft (bomber, transport), the R-1820 should be as good as the R-1830. For a single engined bomber (SBD class or similar), my guess is also that R-1830 has no advantage. Sensible choice (due to price) might dictate the R-1820 in these categories.

    The R-1830 was also available in 2-stage supercharged variant from 1941, that is going to give notably more power above 16-17000 ft. OTOH, the R-1820 received, among other improvements, the water injection system, so it will be a better engine under ~12000 ft in late ww2.
     
  3. Shortround6

    Shortround6 Well-Known Member

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    It comes (at least somewhat) from company experience/philosophy. P&W had built two large 9 cylinder radials in the late 1920s

    The Hornet A
    Bore: 6 1⁄8 in (155.6 mm)
    Stroke: 6 3⁄8 in (161.9 mm)
    Displacement: 1,690.5 in³ (27.7 l)

    And the Hornet B
    Bore: 6.25 in. (158.8 mm)
    Stroke: 6.75 in. (171.4 mm)
    Displacement: 1864 cuin (30.54 L)

    Early Cyclone 9 was
    Bore: 6.00 in. (152.4mm)
    Stroke: 6.875 in. (174.6 mm)
    Displacement: 1750 cu in (28.7 L)

    A 1/8in bore job brought it to
    Bore: 6.125 in (155.6 mm)
    Stroke: 6.875 in (174.6 mm)
    Displacement: 1,823 in³ (29.88 L)

    Pratt Whitney had some troubles with the large Hornet with burned pistons which were not occurring with the small Hornet and decided that smaller cylinders would be less trouble. NO production P&W engine used cylinders of the Hornet B size again. The R-2800, R-4360 and R-2180 (post war) ALL using Bore: 5.75 in. (146 mm) X Stroke: 6.00 in. (152 mm) cylinders.
    Better fins and different piston design/materials might have helped but P&W decided that more smaller cylinders offered better cooling and a easier path to higher power.

    Wright eventually got the R-1820 to much higher power levels than the R-1930 ever got to but these engines shared nothing except the bore and stroke of the older engines.

    Old joke from the 1930s was that you could tell what kind of engines were in a DC-3 by looking at the pilot/s several hours after they landed. The pilots that flew Cyclone powered planes had arms that were still shaking :)
     
  4. rogerwilko

    rogerwilko Member

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    Thanks chaps. And unit cost comparison?
     
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