drive line

Discussion in 'Powerboats' started by seacat, Dec 11, 2012.

  1. seacat
    Joined: Dec 2012
    Posts: 22
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    Location: cebu philippines

    seacat boatbuilder/designer

    hi,

    would like to ask best drive line option for my newly built twin 360hp diesel x 140 pax, 65 feet x 24 feet steel hull catamaran boat.

    Details:
    17'-3" horizontal distance from transom to tranny
    23" vertical distance from keel to tranny coupling (center) @ engine side
    6" vertical distance from keel to shaft @ transom side
    36" horizontal distance from transom to propeller

    im using to double universal joints with spline ( sequence: propeller connected to 7' x 2.5"D 304 ss shaft - double universal joint with coupling- 11' x 2.5" D toll steel- double universal joint with coupling connected to tranny) my problem is the drive line angle. would it be possible to use the zero degrees angle to get optimized speed and no resultant thrust or take the 9 degrees down angle to get the straight shaft from propeller to tranny?

    Thank you,
    seacat
     
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Firstly, are you saying you built a commercial vessel and didn't design the powerplant yet? There is no way to answer your question without a set of lines with construction details, specifications for the engines, etc. The structure and layout will determine engine placement, which in turn will limit the installation. If you are going to use U-joints, it makes more sense to install them as a jack shaft so there is no need of complicated thrust bearings, pillow bearings, etc.
     
  3. seacat
    Joined: Dec 2012
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    Location: cebu philippines

    seacat boatbuilder/designer

    sir Gonzo san, the powerplant twin 360HP intercooler diesel engines and already mounted in the engine bay. the boat lightship 22 tons and loaded displacement of 32 tons. transom mount drive system seafury concept though a hard water propeller 28"diameter x 34" pitch 4 bladed. my concern is the vibration and the optimize shaft angle. the thing im concern with is the resultant thrust for the 9 degrees down angle or the ventilation for the zero degrees angle. a prototype catamaran design wave piercing hull.

    akihiro watanabe
     
  4. El_Guero

    El_Guero Previous Member

    WOW. If you are concerned about vibration, you might have a problem with your drive line, mounts, framing in the hull. The transmission. The engine itself. Most often universal-joints cause the vibration problem. But, it can be just about any mount, or connection in your drive train - even the propellers themselves could be out of balance.

    At what speeds do you notice the problem?

    A 14 year old Catamaran? Yes, it could need new u-joints. But, it COULD be something else.

    Good luck!
     
  5. Frosty

    Frosty Previous Member

    Through Seafury concept or Seafury drive system.

    You mean you copied a Seafury Surface drive?

    Post pics.
     
  6. El_Guero

    El_Guero Previous Member

    Frosty,

    Look at the photo on his profile.
     
  7. Frosty

    Frosty Previous Member

    He has'nt built it yet.
     
  8. El_Guero

    El_Guero Previous Member

    Read the name on his catamaran in his profile photo ....

    :)
     
  9. Frosty

    Frosty Previous Member

    its not a photo --it an artists impression.
     
  10. El_Guero

    El_Guero Previous Member

    You might be right.

    But, I think he needs new u-joints.
     
  11. seacat
    Joined: Dec 2012
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    Location: cebu philippines

    seacat boatbuilder/designer

    @ frosty san- sir not copied from seafury, the concept is at transom mount. will post pics asap.
    @ El_guero san - sir thats my worries now, the vibration, the optimized angle, and the resultant thrust - the boat is already done, last thing to fit are the cooling system and the drive shaft. Engines are already mounted inside the engine bays. - i have in hand are double universal joints with spline ....
     
  12. Frosty

    Frosty Previous Member

    Looks like your committed far enough to give it a try. I have to admit I dont understand your transom mount drive.

    Fit your UJ's opposing each other , that may help in cancelling out vibration.

    But where is the thrust going if you have a spline?

    Im gonna need some pics.
     
  13. seacat
    Joined: Dec 2012
    Posts: 22
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    Location: cebu philippines

    seacat boatbuilder/designer

    @ frosty san- posting pics now for the stern tube with flange to be mounted at transom, together with cutless bearing, lignum vitae bearing, shaft seal... theres are thrust pad with thrust bearing (7 tons dynamic thrust load capacity) fitted at the shaft between the shaft seal and the uj's.
     
  14. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Seacat, why are you so concerned with vibration? From an engineer's point of view you've done everything by the book. Let the U-joints enjoy a small angle, just enough to keep the needle bearings occupied without causing noticeable variations in angular velocity.

    If any vibration is transmitted to the hull it will be through the engine mounts. Because there is no thrust force, the mounts need only cope with torque, so they can be very flexible.
     

  15. seacat
    Joined: Dec 2012
    Posts: 22
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: cebu philippines

    seacat boatbuilder/designer

    CDK, thank you very much for the vital info regarding vibration and u-joints job. originally the set-up was 9 degree down angle. though im thinking and asking your expertise sir CDK, what would u recommend, zero degree angle or 9 degree angle as engineer's point of view. ? thank you sir in advance...
     
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