Hurth HBW 50 gearbox, use any direction as "forward"?

Discussion in 'Inboards' started by Morro, Nov 4, 2009.

  1. Morro
    Joined: Apr 2008
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    Location: Norway

    Morro Junior Member

    On this gearbox, with a different ratio for what they call position "A" and "B", can I choose what is now used as reverse to be forward, with a propeller for the opposite direction?

    Is it correct that this gearbox can be used for running in either direction, and some others needs forward to be forward?
     
  2. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    On this transmission, RH rotation (ie opposed to engine rotation) is forward. In fwd you have ratio 2.05:1 or 2.72:1, and in reverse 1.86 for both. The reason is that in fwd all power is transmitted over one set of gear wheels, while in reverse it passes two gears and a layshaft.

    Because of this, the max allowed power in reverse is reduced to 0.5 hp / 100 rpm (0.7 hp / 100 rpm in forward).
     
  3. Morro
    Joined: Apr 2008
    Posts: 21
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    Location: Norway

    Morro Junior Member

    Thank you for the info.

    I am thinking about using reverse as forward, to get the 1,86 gear ratio. Since it is a 10 hp /3000 rpm engine it should be ok then, even if it is not optimal, probably slightly more power wasted to heat in the transmission.

    Or is the reverse gears designed for very little use, or will forward thrust be a problem in reverse?
     

  4. baeckmo
    Joined: Jun 2009
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    Likes: 127, Points: 63, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    Your numbers seem ok. As there is no mentioning of any other limit than input power, we must conclude that both directions are ok, provided you keep the power within limits.
     
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