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What is torque?

Discussion in 'Technical Discussion' started by tirekicker11, Nov 20, 2010.

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  1. tirekicker11, Nov 20, 2010
    #1
    tirekicker11

    tirekicker11 Senior Member

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    I have been reading about torque and reduction gears and I don't understand it at all.
    I thought that the idea was to make a propellor turn as fast as possible in order to displace as much water as possible but now I read that the gearbox reduces the revs from the engine in order to give more torque to the prop.

    I have been looking everywhere but I can't find an answer I understand.
  2. NYCAP123, Nov 20, 2010
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    NYCAP123

    NYCAP123 Senior Member

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    Torque is 'turning force' as in the force or pressure you use to turn something. In different applications bolts, nuts, even jar lids, etc. have to be tightened with a certain amount of pressure to keep from backing off. A torque wrench measures the pressure applied. A prop needs a certain amount of pressure to turn through the water and push the load (boat). Reduction gears reduce the turning speed of the shaft as opposed to the cam to increase torque. This explains it pretty well.
    http://www.teamdavinci.com/understanding_gear_reduction.htm
  3. tirekicker11, Nov 20, 2010
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    tirekicker11

    tirekicker11 Senior Member

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    Thanks NYCAP but that's the part that I do understand.
    What I don't understand is why you would reduce the rev's (of the prop) in order to gain torque. What I thought is that you want the prop to do high revs in order to provide speed.
  4. NYCAP123, Nov 20, 2010
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    NYCAP123

    NYCAP123 Senior Member

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    Ever drive an underpowered, manual shift car up a steep hill? If you hit it in high gear doing 60 you'll soon be doing 30 unless you downshift. Your transmission is a reduction gear, in fact multiple reduction gears because cars experience multiple pressures (conditions). Boats generally only need one because the pressure is generated by the weight of the boat (load). Different boats will need different ratios to handle different loads. A speed boat's load is far different from that of a tug although (theoretically) the could use the same motor.
  5. tirekicker11, Nov 20, 2010
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    tirekicker11

    tirekicker11 Senior Member

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    Thanks NYCAP,

    That explains a lot.
    So in theory it might be possible that certain designs don't use a reduction gear at all?
  6. NYCAP123, Nov 20, 2010
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    NYCAP123

    NYCAP123 Senior Member

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    Sure, maybe like a hydroplane that's going for maximum speed; pushing very little wait against almost no resistance and that doesn't mind blowing an engine in that pursuit if it over-revs.
  7. tirekicker11, Nov 20, 2010
    #7
    tirekicker11

    tirekicker11 Senior Member

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    Got it, thanks NYCAP!