gearbox ratio calculation

Discussion in 'Props' started by enmico, Apr 10, 2013.

  1. Roberto Certain
    Joined: Apr 2021
    Posts: 9
    Likes: 0, Points: 1
    Location: Colombia

    Roberto Certain Junior Member

    Or a conventional shaft if I have the space.
  2. rxcomposite
    Joined: Jan 2005
    Posts: 2,402
    Likes: 394, Points: 83, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    We built a lot of stern drive patrol boats with Volvo Penta engines. Volvo's are known for lightweight high speed diesels and as such, its use is for low to medium duty cycles. Overhauls, not necessarily failures is more frequent if you load it most of the time. This is called duty ratings. Engines with high duty ratings (loaded most of the time) are heavy, slow turning, and beefy. We reserve that for fishing boats. Better check what duty cycles you intend to use your boat. Most of the time, the engine choice is the problem, not the gear. There are 5 duty ratings for engines. Sometimes as much as 6.

    If you are convinced about the V drive, the best advice you can get is from the supplier of the transmission. They are going to ask you about the ship particulars, type of hull, engine to be used and your intended use. They are usually spot on in giving advice.
  3. comfisherman
    Joined: Apr 2009
    Posts: 165
    Likes: 66, Points: 28, Legacy Rep: 10
    Location: Alaska

    comfisherman Senior Member

    With an existing hull is difficult because you're working within the constraints of adaptability we're starting from scratch and shooting for Optimum. This is the trade-off that so many boat projects always face.

    I would mock up shaft dimensions and v drive configurations to see what size wheel you will be able to swing. Decide on diameter maximum and then you have two endpoints to work with.

  4. Adler
    Joined: Jan 2010
    Posts: 180
    Likes: 15, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Think about a solution .....
    2 x Engines 120hp at 2400 rpm
    2 x Gearboxes Ratio 1: 1.57
    2 x Propellers Dia 470mm Pitch 470mm 4 blades GawnAEW Blabe Area Ratio : 0.70
    2 x Propeller Shafts Dia:50mm Material: 316L

    Cruise Speed 15 kts at 2170 rpm
    Max. Speed 17+ kts at 2400rpm
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.