Single engine / dual shafts?

Discussion in 'Boat Design' started by dreamer, Apr 26, 2009.

  1. ben2go
    Joined: Jul 2008
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    Location: Upstate, South Carolina,USA

    ben2go Boat Builder Wanna Be

    What about using hydraulic pump and motors?Never done this on a boat.
     
  2. apex1

    apex1 Guest

    Because the noise will drive you nuts before you cross the port entrance. And hydraulics leak sooner or later (usually sooner).
     
  3. Boston

    Boston Previous Member

    the basic father and son rig running one screw was not uncommon on many of the old lobster boats we worked on
    kinda the oposite of what your original question was but its fuel efficient
    the maneuverability issue was handled beautifully at the start by someone when they basically said
    learn how to drive

    if you had one huge engine and enough torque and extra power to run twin screws you would be wasteful enough already
    but adding two transmissions and a transfer case and your going to be selling the children to pay for fuel

    on the other hand
    to each his own
    if its really what you want go for it
    if you placed the screws far enough apart you just might be able to do a spin

    cheers
    B
     
  4. ben2go
    Joined: Jul 2008
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    Location: Upstate, South Carolina,USA

    ben2go Boat Builder Wanna Be

    I can agree to that.
     
  5. Jim_Hbar
    Joined: Sep 2006
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    Location: Pac NW

    Jim_Hbar Junior Member

    Dreamer:

    I've pondered the advantages of the drive system you have proposed, and although the hardware might not exist at this time, adaptable components may be available in the near future. Google "toroidal cvt".

    I believe one large potential benefit not mentioned in the above posts, would be the possibility of eliminating rudders and the associated appendage drag. And the second would be the ability to load the engine into an efficient operating range. Both of these items would allow the vessel to operate at significantly increased efficiencies.

    Will it be a system for everyone, and all applications? Not likely, unless it becomes fully developed by one of the majors. But if fuel becomes expensive enough, and the CVT technology matures in the automotive market, the economics may change sufficiently to warrant the capital and maintenance costs associated with such a complex mechanical system.

    Just my 2 cents.

    Jim
     
  6. apex1

    apex1 Guest

    Well Jim, how would you eliminate the rudders? And why? A twin engine twin prop system does not eliminate them (for about 57,5 good reasons).
    And if you want to load the engine sufficiently (a very good idea with a Diesel) you should use a common and very reliable CPP instead.
    There is just NO need for a system with a single engine two props!
    Regards
    Richard
     
  7. Boston

    Boston Previous Member

    gotta go with Apex on that one
    you would find yourself wanting a rudder in about the first trip out of port when you had one running full reverse and one full forward and you were still heading towards the breakwater

    thing you are after if you want to eliminate the ruder is vectored thrust
     
  8. ben2go
    Joined: Jul 2008
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    Location: Upstate, South Carolina,USA

    ben2go Boat Builder Wanna Be

    Just tossing out ideas,but how bout a single prop with a kitchen rudder.This will eliminate the need for a transmission.You'll still need a reduction box if your engine spins above a certain RPM.A kitchen rudder gives reverse,neutral,side thrust,and forward thrust without having to adjust engine speed.

    http://www.proboat-digital.com/proboat/200608/?pg=63

    http://www.boatdesign.net/forums/boat-design/kitchen-rudder-418.html

    http://en.wikipedia.org/wiki/Kitchen_rudder

    http://www.oldmarineengine.com/discus/messages/5/1010.html
     
  9. ben2go
    Joined: Jul 2008
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    Location: Upstate, South Carolina,USA

    ben2go Boat Builder Wanna Be

    Forgot to add that one engine and two props will not give more thrust.The drag plus the loss of powering two props and gear will cut down the power at the props.It will kill effieciency also.The engine will have to work twice as hard to turn two props and over come the extra drag of the gear.
     
  10. Boston

    Boston Previous Member

    Kitchen ruder = vectored thrust
    course I had never seen a kitchen ruder before other than on a jet turbine as a brake
    but that kitchen ruder is exactly what vectored thrust is



    in this next video you can clearly see a type of Kitchen ruder being applied to a jet engine as a braking mechanism

     
  11. apex1

    apex1 Guest

    Thats all very nice mates, but we can discuss Azipods, Kort Nozzles, Voith Schneider propulsion and the like a several hundred times more. I do´nt see a benefit in a single engine two shafts installation, thats all! And thats all what originally was asked for.
    Regards
    Richard
     
  12. Jim_Hbar
    Joined: Sep 2006
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    Location: Pac NW

    Jim_Hbar Junior Member

    Richard:

    One engine driving two final drives has been used for years, just not in mainstream marine propulsion applications..

    And if one was to attempt that in a marine application, then CPP's would likely be the prime candidate, at least initially. They have the advantage of going from forward through neutral to reverse that is absent from the forms of CVTs that are used in the automotive world (and would likely be adapted to the marine world , if it ever occurred).

    IIRC, Yellowfin proposed the two drive, surface piercing, CPP with rudderless control - and AFAIK, proved that it was not economically viable at this time also. Unfortunately, much of the content that was available on their web site is no longer up, but others on this forum are very familiar with their offering - perhaps they will chime in.

    Dreamer, the thread starter, originally asked about CVTs. I was staying on topic, and my post was directed to him specifically. The point I was attempting to make was that such a system is likely not commercially viable at this time. But "Can" and "Should" are two different questions. I am attempting to provide input to the "CAN" question.

    There are other threads on this forum that are discussing many things outside of the mainstream - ie: Boston's thread on external combustion engines, or the old DDWFTTW thread.. And in many, people jump in and say - "That's not the way we do it - it can't be done!"

    And responding to your summary -
    - I would add there is "just NO need" for twin engines with twin props, or boats that plane, or even recreational boats that use anything other than paddles or sails.

    Jim
     
  13. apex1

    apex1 Guest

    Well, Jim one question was not answered in your post: how and why would you eliminate the rudders? Pod´s are out of the race already.
    Regards
    Richard
     
  14. Jim_Hbar
    Joined: Sep 2006
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    Location: Pac NW

    Jim_Hbar Junior Member

    Richard:

    Rather than resorting to personal attacks and implying I am a liar, I suggest that you go look at a tracked machine, whether it be a crawler tractor (CAT), or a tank, for an example of a prime mover driving two final drives. One could even consider an automobile to normally have at least two outputs, although they typically do not control the torque distribution to the driving wheels, so are not a good example in this case. All have two (or more) power outputs from a single engine..

    I believe this "boat" works without rudders also, two final drives, one engine..

    I've only stated my opinion, that I believe the CVT approach is not commercially viable at this time, and mentioned the example of the Yellowfin, which I understand is/was a rudderless system. You have ignored that in your reply. Personally, I'm not interested in engaging in pissing matches on forums, I have much better uses for my time.

    The "Why" for eliminating the rudders? Reducing the appendage losses of course.... :D Is it possible? In some applications, perhaps.

    I gather you want your name taken off of the pre-order list??:(

    Jim
     

  15. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Price out your transmission costs for 1 engine 2 props. Do that and you will desire 2 engines. You are insulting folks that build many yachts and you are going on an idea only---not experience. We try to help here and if you do not like the help then just go to other places. that is a simple solution and does not require put downs. I'm just a simple small wood boat builder and try to give good advise-- that's all.
     
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