Gear an torque In/Out

Discussion in 'Diesel Engines' started by Lee01, Aug 2, 2013.

  1. Lee01
    Joined: May 2012
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    Location: Italy

    Lee01 Junior Member

    Hello, I'd like to understand something about torque and gear,
    for the selection of a drive model

    I am sure that Rpm speed is divided by reduction ratio, for example 3300 rpm at crank will output 2000rpm at the propeller:

    what about Torque? Is it divided by 1,55 also or multiplied? and horsepower?


    Thanks :)
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If the RPM are reduced, the torque is multiplied by the same ratio. There are frictional losses that depend on gear design, but you can estimate roughly at about 3%.
     
  3. Lee01
    Joined: May 2012
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    Location: Italy

    Lee01 Junior Member

    simple question simple answer =) thank you!
    so power in hp will be divided also? or it remain the same (less3%) ?
     
  4. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Power remains the same less any losses (frictional, oil churning, etc).
     
  5. Lee01
    Joined: May 2012
    Posts: 36
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    Location: Italy

    Lee01 Junior Member

    fine :) so the gear only trade rpm in torque, and the power remain the same more or less, I also found this torque calculator based on power * speed
    http://www.wentec.com/unipower/calculators/power_torque.asp
    is it right for non-electrical engines where performance chart are not linear?

    also why permormance charts are not linear? power and fuel use aren't proportional with rpm of the engine?
     

  6. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    Power = Torque X Rotational Speed (with appropriate unit conversion factor)

    Torque = Power / Rotational Speed (with appropriate unit conversion factor)

    Rotational Speed = Power / Torque (with appropriate unit conversion factor)

    The relationships above hold for any rotating system, including Diesel engines, gasoline engines, electric motors, steam engines, windmills, water wheels, steam turbines, gas turbines and squirrel cages.

    Torque varies with speed of the engine which is why power is not proportional to the speed of the engine. Fuel use of an engine depends on a number of factors.
     
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