Weismann Surface drive with transmission

Discussion in 'Surface Drives' started by OCB, Jan 3, 2018.

  1. OCB
    Joined: Dec 2015
    Posts: 94
    Likes: 5, Points: 8, Legacy Rep: 10
    Location: USA

    OCB Junior Member

    Last edited: Jan 7, 2018
    DogCavalry likes this.
  2. HandMan
    Joined: Aug 2015
    Posts: 8
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Dallas, TX

    HandMan Junior Member

    Very cool but I wonder what it's like throttling through heavy seas.
     
  3. DogCavalry
    Joined: Sep 2019
    Posts: 2,127
    Likes: 1,076, Points: 113
    Location: Vancouver bc

    DogCavalry Soy Soylent Green: I can't believe it's not people

    This is fantastic! I love the discussion of the linked article, and the video showing the transmission gearing up during different phases of acceleration.
     
  4. DogCavalry
    Joined: Sep 2019
    Posts: 2,127
    Likes: 1,076, Points: 113
    Location: Vancouver bc

    DogCavalry Soy Soylent Green: I can't believe it's not people

    And the engine layout!
     
  5. DogCavalry
    Joined: Sep 2019
    Posts: 2,127
    Likes: 1,076, Points: 113
    Location: Vancouver bc

    DogCavalry Soy Soylent Green: I can't believe it's not people

    Question. For those who didn’t follow the link, the fellas who built this boat used a brilliant engine arrangement, but they also used a pair of auto transmissions with the LS7’s. The video shows the boat running up through the gears, from getting on plane to well above a hundred mph. They won every race they ran in. 11 in a row. Until the league banned auto engines, so their boat couldn’t compete anymore. Sore losers.

    Anyway, since it’s been established elsewhere that multi speed transmissions are useless in boats, it doesn’t make sense for the league to ban them. They’d only be worth banning if they gave an unfair advantage. Which they wouldn’t do, unless the multi speed transmission gave significant performance advantages, which we know it doesn’t.

    And even then, it still doesn’t make sense. If they’d beaten me, I’d just adopt what they did and beat them at their own game.

    So can anyone help me understand how they used a 3 speed transmission to advantage?
     
    Last edited: Nov 16, 2019
  6. DogCavalry
    Joined: Sep 2019
    Posts: 2,127
    Likes: 1,076, Points: 113
    Location: Vancouver bc

    DogCavalry Soy Soylent Green: I can't believe it's not people

    Not much of that in a massively powerful raceboat.
     
  7. powerabout
    Joined: Nov 2007
    Posts: 2,931
    Likes: 66, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    The success of the diesel powered offshore race boats was down to the multi speed boxes they ran.
    The multi speeds were what was banned, that killed he diesels off.
    The rpm range of a diesel is small hence they needed gears to get on the plane then turn the prop for speeds well over 100mph
     
    DogCavalry likes this.
  8. DogCavalry
    Joined: Sep 2019
    Posts: 2,127
    Likes: 1,076, Points: 113
    Location: Vancouver bc

    DogCavalry Soy Soylent Green: I can't believe it's not people

    I thought as much. Lot of fellas on the forum are broken records: Multispeed transmissions don't exist, or serve no purpose.
     
  9. baeckmo
    Joined: Jun 2009
    Posts: 1,337
    Likes: 309, Points: 83, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    The point here is the power absorbtion characteristics of the ventilated/surface piercing propeller; it differs radically from a submerged prop. With increasing submergence (as with reduced forward velocity in a planing vessel), the torque is increasing above the available torque from the engine. Ergo, the prop can't spin to accelerate the boat, because the engine is bogging down.

    One alternative remedy is to introduce "extra ventilation gas" during the submerged operating phase, another is to raise the prop shaft (as with the Arneson's). But both these mean that the ventilated prop is operating in the range of low advance factor, where the thrust is limited. A normal, submerged prop has thrust and torque factors that continually increase with reduced advance (higher load), but the spp has a peak for both thrust and torque, falling at both sides of the maximum.

    So you can not draw any general conclusions about the suitability of multispeed transmissions from an example of a racing surface piercing propeller's performance. In fact, that goes for supercavitating propellers as well. Many of the bigger SC ones were driven by twin shaft gas turbines, which act much like a stepless variable transmission. That solved the torque/thrust dilemma there.
     
    BlueBell likes this.
  10. BlueBell
    Joined: May 2017
    Posts: 1,973
    Likes: 583, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . . .

    That's the coolest video I've seen in awhile, thanks.
    What a shame gearing just doesn't work on boats.

    The pictures didn't show on the link. Rats.
    Edit: I left clicked over one of the empty photo spots and gained access to all 15 pictures.
    Somebody spent a lot of money.
    Note: Flaps not trim-tabs.
     

  11. DogCavalry
    Joined: Sep 2019
    Posts: 2,127
    Likes: 1,076, Points: 113
    Location: Vancouver bc

    DogCavalry Soy Soylent Green: I can't believe it's not people

    @baeckmo , there's no need to draw conclusions about the suitability of multispeed transmissions from any single data set, such as the weisman setup in the OP's first post. @powerabout 's response is a more than adequate second set. And the universal use of multispeed transmissions in too fuel drag boats is another. And the fact that every single guy who posts here, who has actual experience with them, rather than quoting what "everybody knows" speaks in their favour is an embarrassment of riches.
     
Loading...
Similar Threads
  1. IMP-ish
    Replies:
    0
    Views:
    3,680
  2. slowrunning
    Replies:
    22
    Views:
    3,146
  3. sandhammaren05
    Replies:
    0
    Views:
    1,101
  4. Christian Lucas
    Replies:
    11
    Views:
    1,796
  5. MRover
    Replies:
    2
    Views:
    1,384
  6. James Little
    Replies:
    7
    Views:
    3,452
  7. OCB
    Replies:
    8
    Views:
    4,002
  8. crowsridge
    Replies:
    7
    Views:
    3,303
  9. Irie
    Replies:
    62
    Views:
    26,608
  10. mydauphin
    Replies:
    1
    Views:
    2,844
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.