(Request) thrust of a B29A engine-propeller combination

Discussion in 'Flight Test Data' started by msxyz, Oct 5, 2012.

  1. msxyz

    msxyz Member

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    Does anybody have a figure for the maximum static thrust developed by a single R3350 (2200 hp) engine when mated to the 16ft propeller used by the Boeing B29?

    Thanks!
     
  2. krieghund

    krieghund Member

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    I think this will be hard to come by. The rule of thumb is multiply the take off horsepower by a factor of 2.5 to approximate static thrust which is about 5,500 lbs. To calculate an exact figure you'll need the propeller performance perameters.
     
  3. drgondog

    drgondog Well-Known Member

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    Krieghund is right. Simply stated, calculating 'thrust' equivalence with a propeller/engine system whose primary performance is horsepower is a formula based an propeller performance, Hp at a given set of atmosperic parameters of which altitude is the primary factor and the attained velocity of the system being studied.

    Short answer - "It gotta move" to start the derivation of equivalent thrust based on the change of the mass flow rate through the prop/engine system in flight. The faster the system moves the less thrust is developed as the change in the mass fow rate from the conditions in front of the prop to that in the stream tube aft - is less.
     
  4. msxyz

    msxyz Member

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    Thanks for the answers, that's why I specifically asked for the engine-propeller combination of a B29: knowing the horsepower of the engine is not enough to know how much force is developed.

    Since propeller efficiency decreases as the aircraft to which is attached gains forward speed, would it be correct to say that 'static thrust' for a propeller driver aircraft is the maximum obtainable by such a propulsion system?
     
  5. Shortround6

    Shortround6 Well-Known Member

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    Propeller efficiency may not decrease as the plane gathers forward speed. It depends on the propeller. Fixed pitch props vary enormously in efficiency at low speeds (static) which is one reason for variable pitch props. Not all variable pitch props can go to zero pitch. Some had a lower limit of 20 degrees or so.
     
  6. drgondog

    drgondog Well-Known Member

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    Variable pitch Propeller efficiency increases in most cases to ~ .85 asymptotically as velocity increases up to a 'point'.

    Thrust decreases with velocity. It is probably safe to say that static bench thrust is close to maximum attainable for a specific set of pitch/rpm criteria.
     
  7. wells

    wells Member

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    best case ( standard sea level ), results rounded to nearest 100 lbs

    0 mph ( static ) ~ 4000 lbs
    50 mph ~ 3100 lbs
    100 mph ~ 2400 lbs
    150 mph ~ 1800 lbs
    200 mph ~ 1400 lbs
    250 mph ~ 1200 lbs
     
  8. drgondog

    drgondog Well-Known Member

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    Wells - those number look reasonable but there is a curious anomaly - namely 2400 lbs at 100mph and 1400 at 200mph (instead of '1/2' the 100mph thrust results for '2x' velocity)

    Did you get a variance of 'eta' between 100 and 200 mph to offset the linear relationship with inversely proportional speed?
     
  9. Aozora

    Aozora Well-Known Member

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  10. wuzak

    wuzak Well-Known Member

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    Those links don't work for me.
     
  11. wuzak

    wuzak Well-Known Member

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    #11 wuzak, Dec 23, 2012
    Last edited: Dec 23, 2012
  12. Aozora

    Aozora Well-Known Member

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    #12 Aozora, Dec 24, 2012
    Last edited: Dec 24, 2012
    Yep: I haven't read them properly, but a quick skim through indicates they don't show the maximum static thrust figures that msxyz is looking for. Nevertheless they are interesting. Apologies for the garbled links in the previous posting. Cheers

    PS: Hope one and all have a great Christmas!
     
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