Connecting two shafts / diameter is restricted

Discussion in 'Propulsion' started by ldigas, Jun 15, 2011.

  1. ldigas
    Joined: Feb 2011
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    ldigas Senior Member

    First, my apologies if this is not the right place for this question on the forum. I wasn't sure, but couldn't find any better.


    What would be a good way to connect two shafts (tail and intermediate) of diameter 65-70mm, when there is a problem with space. I could use the standard coupling but am looking for something that has smaller outer diameter, that is - I have a problem with space where the couplings should go.

    All practical advice or links or any source of information would be welcomed. The power of the engine in question, (if that matters) is bout 300 kW. The length of the entire shaft (both of them connected together) is approximately 6,4 m.
     
  2. gonzo
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    gonzo Senior Member

    You can use a split coupler.
     
  3. tunnels

    tunnels Previous Member

    A shaft that long will need a hanger bearing or two to support the shaft . What sort of rpms is it likely to spin at ?? :confused:
     
  4. ldigas
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    ldigas Senior Member


    I believe (not at my desk now, so I may be off a bit, but I'm fairly certain) 1360 rpm, at full power of 324 kW (440 hp metric).
    The "configuration" of the shaftline (not sure whether this is the exact term used) is as follows;

    - propeller at the tail end of tail shaft
    - strut right in front of it
    - about 2m of shaft in water
    - shaft then enters the stern tube of about 2m in length, which is connected to the skeg and which "enters" the hull
    - after that comes the coupling of the two shafts

    - front shaft - about 2m in length total, which leads to the engineroom ...

    So, generally, the tail shaft is "supported" at every 1/3 of its length, give or take. With the front shaft I don't expect any trouble.

    Can you offer some advice given the situation? Are there any problems I can expect?

    The problem with the yacht was in the fact that it had a very thin skeg (breadth wise) and the stern tube is wider than the skeg at almost 2 frames length (800mm), so the skeg at that part is really welded to the stern tube, so to speak.


    Hope this makes some sense ...
     
  5. ldigas
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    ldigas Senior Member

    Thought of that, only I haven't seen them used at those diameters. Maybe it's just that I haven't seen enough of them.

    Can you perhaps tell whether at 324kW/1350rpm I could expect some trouble with them. Also, from your experience, for a 70mm shaft (diameter) what would be the approximate outer diameter of a split coupler?
     
  6. Landlubber
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    Landlubber Senior Member

    1360 rpm, at full power of 324 kW....that is the engine of course, not the shaft speed, you need to state the ratio of the box too.
     
  7. ldigas
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    ldigas Senior Member

    Mea culpa. I should've put it more clear - that is the shaft speed! The engine runs at 3000 rpm (or something like that).
     
  8. Adler
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    Adler Senior Member

  9. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    There are many good succestion already, but here's one more. If you can get the shafts to a good machine shop, splines could be machined to both shaft pieces. Spline couplers should be easy to find.

    Another, I have used bearing glue (Loctite 648 etc.) for multiple application myself. The stuff has pretty impressive properties for this kind of use.

    Lurvio
     

  10. BMcF
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    BMcF Senior Member

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