Welded metal belows - would that work for sterndrive?

Discussion in 'Sterndrives' started by Nidza, Oct 18, 2023.

  1. Nidza
    Joined: Nov 2016
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    Nidza Senior Member

    Is it possible to use welded metal belows for sterndrives, if custom one could be built to replace the existing one? Could that be a "permanent" solution?

    Here is one example of what are some possibilities:
    Configuration - Werte Kollegen und Kolleginnen, konfiguriert Eure individuellen Metallbälge! https://www.bellows-configurator.com/

    Hmm, what would be the best material (316L sounds nice, but could lead to galvanic corrosion, depending on the type of attachment between the drive and below, just one of thoughts)? What type of connection would be ideal instead of clamps?

    I would appreciate your thoughts.
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I am sure that if it was possible to make a flexible bellows for a stern drive unit out of metal, somebody would have done it by now.

    In your link they ask you to choose the number of cycles required - stainless steel does not have a very good fatigue life, unlike a material like rubber.
    Think about how easy it is to break a piece of steel plate by simple fatigue (eg bending it to and fro).
    But you can bend a sheet of rubber endlessly, and it will not break.
    If you had a bellows made from stainless steel, then every change of course while underway would probably add an extra fatigue cycle (not to mention other effects like vibration) and it would no doubt fail very quickly.
    DogCavalry and gonzo like this.
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Those bellows are for vibration and small movements, not the displacement and twist required of a rubber bellows. Rubber lasts for several years, and is cheap. I think that it would be possible to use a better synthetic rubber, although the price would be higher.
    bajansailor likes this.
  4. kapnD
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    kapnD Senior Member

    Gonzo is right.
    I’ve always thought that the bellows could be built better, possibly with Kevlar fabric/rubber.
    As they come, they’re fairly reliable, as long as they’re kept clean and changed out periodically.
    No different than the rest of the rubber parts on a boat, it’s not a piece to run until it breaks!
    bajansailor likes this.

  5. Nidza
    Joined: Nov 2016
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    Location: Belgrade, Serbia

    Nidza Senior Member

    OK, thank you all for clarificartion. It makes sense.
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