Is my old Volvo coupling good to use?

Discussion in 'Inboards' started by Runhammar, Jan 24, 2023 at 9:17 AM.

  1. Runhammar
    Joined: Jul 2020
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    Location: Stockholm

    Runhammar Junior Member

    Together with an engine that I just picked up, there is a shaft coupling, which I'm guessing is an old design. Most modern couplings that I see consist of two halves that are tightened together by at least six machine screws. This one is one piece, doesn't "grab" the shaft and is held by a key in a keygroove and one single machine screw. I'm guessing most of you will know which one I am talking about.
    Now, reusing this coupling could possibly save me one hundred dollars, so I am curious as to whether it is as reliable as the other ones that "grab" the shaft. The key in the groove should absolutely prevent it from turning freely, but what about that single screw holding it i place? The engine itself would stop the shaft from going forward, but what about reversing? Could I end up with the propeller pulling the shaft out of the coupling? If I wanted to reuse this I would need a keygrove in my shaft, which is possible to make. I have access to a milling machine.
    I just posted another question, about flexible couplings. Just to be clear: this is not instead of a flexible coupling, but one of them, the R&D type, must be completed with a simple shaft coupling. Hence the question whether I can reuse the one I have.
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    As long as it has a tight fit, there should be no problem.
     
  3. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Presuming without pictures is dangerous, there are several one piece couplers.
    One relies on an interference fit and has a small setscrew (grubscrew) in addition to the keyway.
    There are also tapered couplings that have setscrews.
    Split couplings can have only one screw providing the clamping.
    There are also more exotic couplings using pins going completely trough the shaft, or one clamping screw that also engages into a recess cut into the shaft.

    But, regardless of what you have, if the coupler is sound and tight on the shaft you are probably good to go. If you need to remove and reinstall it you should know what type you have to follow proper procedure.
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    One issue to check is that the faces of both couplings, shaft and transmission, are square. That is, the face is at 90 degrees from the centerline.
     

  5. Runhammar
    Joined: Jul 2020
    Posts: 27
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    Location: Stockholm

    Runhammar Junior Member

    Good thoughts, thank you. I will check for square, and probably reuse the old coupling, provided it is a tight fit.
     
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