Bristol Hercules: how many HP at altitude?

Discussion in 'Aviation' started by tomo pauk, Oct 14, 2012.

  1. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Could someone please provide good data about the Hercules' power at altitude? The data I have is from the chart found at the AEHS site (cca 1390 Hp at 5100 ft, and 1220 HP at 13000ft, all while using +6 lbs/sq in at unknown RPM); at 20000 ft the chart gives 900 HP.
    The entry at WIlliams' site mentions the +8 lbs/sq in at 2900 rpm, the full throttle height with ram effect being 8,500 ft (327,5 mph) and 15,600 (333,5 mph); at climb the boost was restricted to +6.
     
  2. Shortround6

    Shortround6 Well-Known Member

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    Which models (marks) are you interested in?

    The better WW II Versions ( Marks under 100) seemed to top around around 1545hp at 15,500ft ( no ram?) but there was some variation between Marks
     
  3. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Thanks. I'm interested in any war time marks.
     
  4. Shortround6

    Shortround6 Well-Known Member

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    The figures I gave were for the MK VI and XVI with 100/130 fuel (8.25lbs boost).

    MK III on 87 octane was 1250hp at 16,750ft/4lbs ?
    MK VI on 87 octane was 1265hp at 15,750ft/5lbs ?
    MK X on 87 octane was 1280hp at 16,000ft/4lbs ?

    Figures are from Lumsden's charts in the appendix and unfortunately seem to be another instance of faulty proof reading. HP/boost and altitudes do not track well from one version to another ( or same version with different fuel)
     
  5. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Thanks for the data. Would you be so kind to look at the Wilkinson's book(s), those seem to be accurate? Even if only the latest models are listed.
     
  6. wuzak

    wuzak Well-Known Member

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    From Graham White, Allied Piston Aircraft Engines of WWII

    Hercules XI:
    1315hp @ 2800rpm @ sea level
    1460hp, @2800rpm @9,500ft.

    Hercules VI/XVI:
    1675hp @ 2900rpm @ 4,500ft
    1445 @ 2900rpm @ 12,000ft

    Hercules VII/XVII:
    1735hp @ 2900rpm @ 500ft - cropped impeller

    Hercules VIII: Experimental turbocharged engine

    Hercules XVIII: 1735hp @ 2900rpm @ 500ft
     
  7. wuzak

    wuzak Well-Known Member

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    Hercules VI: 100/130 grade fuel
    Takeoff: 1615hp @ 2900rpm, +8.25psi
    Normal: 1400hp @ 2400rpm, +6psi @ 4,750ft (MS)
    1,300 @ 2400rpm, +6psi @ 13,500ft (FS)

    Maximum: 1750hp @ 2800rpm, +8.25psi @ 6,500ft (MS)
    1545hp @ 2800rpm, +8.25psi @ 15,500ft (FS)

    Hercules XI: 100/130 grade fuel
    Takeoff: 1505hp @ 2900rpm, +6.75psi
    Normal: 1325hp @ 2500rpm, +3.5psi @ 2,500ft (MS)
    1,200 @ 2500rpm, +3.5psi @ 14,000ft (FS)

    Maximum: 1575hp @ 2900rpm, +6.75psi @ 500ft (MS)
    1510hp @ 2800rpm, +6.75psi @ 11,250ft (FS)


    Hercules XVII: 100/130 grade fuel
    Takeoff: 1725hp @ 2900rpm, +8.25psi
    Normal: 1395hp @ 2400rpm, +6psi @ 1,500ft (MS)
    Maximum: 1735 @ 2900rpm, +8.25psi @ 500ft (FS)


    Hercules 100: 100/130 grade fuel
    Takeoff: 1675hp @ 2800rpm, +8.25psi
    Normal: 1515hp @ 2400rpm, +6psi @ 7,750ft (MS)
    1,415 @ 2400rpm, +6psi @ 16,500ft (FS)

    Maximum: 1800hp @ 2800rpm, +8.25psi @ 9,000ft (MS)
    1625hp @ 2800rpm, +8.25psi @ 19,500ft (FS)

    Data from Lumsden.
     
  8. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Many thanks, I'll try to assemble a meaningful table, or to draw some graph(s).

    The Mk.100 is a post-war version?
     
  9. wuzak

    wuzak Well-Known Member

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    Late war.
     
  10. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Hi, wuzak,
    According to Lumsden, The Mk.VI is head and shoulders above the competition at altitude (bar the Mk.100):
    Any thoughts?
     
  11. wuzak

    wuzak Well-Known Member

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    What about the VII/XVII ~ 1700hp @ 500ft?

    I don't hink any of them could be classed as high altitude engines.
     
  12. tomo pauk

    tomo pauk Creator of Interesting Threads

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    That seem to be in the ball park, the VII/XVII.
    I'm not thinking about the Hercules as a dedicated high altitude engines, just were curious about the high altitude capabilities. About those 1545 HP @ 15500 ft for the Mk.VI - a typo maybe?

    BTW, people: what were the main modifications that turned the Mk.100 into a viable high altitude engine? Was it a two stage version? Was there any version with inter cooler?
     
  13. wuzak

    wuzak Well-Known Member

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    No, still a single stage, 2 speed.
     
  14. Shortround6

    Shortround6 Well-Known Member

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    Revised cylinder heads with more fins, a revised crankcase, bigger main bearings in addition to a new supercharger.
     
  15. fastmongrel

    fastmongrel Well-Known Member

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    Apparently early Hercules engines had a very poorly designed supercharger inlet and/or outlet design which choked the airflow. When Sir Stanley Hooker joined Bristol after the war he felt that the Bristol engine design team still didnt understand airflow properly.
     
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