Single engine, dual independent props for cat?

Discussion in 'Inboards' started by Carlazzomark, Jan 25, 2022.

  1. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    Relative newbie here, so please be kind.

    Does anyone know of, or can envision, a single engine driving two independent props, including the ability for counter forward/reverse? Can this be done via separately controlled transmission gear boxes between the motor and each prop?

    The application would be in a larger power multihulls. The advantage seems to me to be less expense (one diesel vs. two), though I do not know what the transmissions would cost, nor how and where the linkage between engine and the drives would look like.

    Just dreaming…
     
  2. fallguy
    Joined: Dec 2016
    Posts: 6,060
    Likes: 1,210, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Where are you going to keep the engine?

    port hull; then you'd need to run a power takeoff up and across the aft cockpit and more transmission down to the cutlass for the starboard prop

    Too many things to fail.
     
    jehardiman likes this.
  3. bajansailor
    Joined: Oct 2007
    Posts: 2,733
    Likes: 1,049, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    I think that system like what you propose would be better suited to a sailing catamaran with 2 small auxiliary propulsion units.
    I remember seeing one with a system like this once, but I can't remember what make of cat it was.
    Nowadays you could maybe look at two electric motors being driven by the diesel engine?
    However for a larger power cat, I think you would be much better off re safety and redundancy if you have two diesels.
     
  4. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    Yes, I was actually thinking about a single diesel-electric powering the two independent props through the gear boxes, so it would be one diesel and one electric engine powering the two props, with the diesel only being used when the battery banks are depleted. One question is would this be a better set-up than one diesel generator, plus an electric motor in each hull.

    My application is for inland water use, so I am not too worried about redundancy.
     
  5. fallguy
    Joined: Dec 2016
    Posts: 6,060
    Likes: 1,210, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    No. Gearboxes is out. It could be done hydraulically I suppose, but not sure it os sensible.

    You would be way ahead with either a diesel engine in one hull and electric engine in the other or a diesel generator and two electrics. Boatbuilderfl is building an electric boat with tesla batteries and the engines actually have regen units on the forward edge. Somehow they calculated a lot of 'free' power was available.

    The reason for this is the other way has too many power trains. For a monohull, it could be done, but a multihull, no.

    As to which is better; the diesel/electric or the generator/dual electric engines; all over again, more moving parts in the latter.

    I have a feeling the diesel and electric combination actually will be a thing with the electric side even including regen.

    Depending upon horsepower needs; as long as you can find enough power; something like a torqeedo and a small diesel engine may even be possible versus an electric inboard which carries more cost.

    This generator and two electric engine solution would have the hurdle of where to place the generator. It would be loud and demand air.
     
  6. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    That’s helpful. Thanks.
     
  7. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

  8. Barry
    Joined: Mar 2002
    Posts: 1,607
    Likes: 355, Points: 83, Legacy Rep: 158

    Barry Senior Member

    Last edited: Jan 27, 2022
    bajansailor and fallguy like this.
  9. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    I ‘ve not heard of this technology. How well does it work, and how does it compare to other propulsion systems? Is there any reason why the pump could not be powered by an electric motor? If so, what would be the advantage over straight electric motor to prop?

    thanks
     
  10. DCockey
    Joined: Oct 2009
    Posts: 5,085
    Likes: 554, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    A "modern" electric drive system will be more efficient than hydraulics and not have the problems of hydraulic leaks and similar.
    How is the power distributed to the prop on each hull? Using mechanical shafts with angle changing gearboxes will probably be expensive and likely to have alignment and maintenance problems.

    A single engine-generator with a motor at each prop is likely to be the most efficient, most reliable and probably lowest cost. Add batteries if operation without the engine running is desired.
     
    jehardiman, DogCavalry and fallguy like this.
  11. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    I agree. Thanks.
     
    Barry likes this.
  12. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    What do you all thinks of this single diesel, two prop system proposed by Hybrid Marine, U.K.:
     

    Attached Files:

    Last edited: Jan 29, 2022
    fallguy likes this.
  13. fallguy
    Joined: Dec 2016
    Posts: 6,060
    Likes: 1,210, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I checked it out and looks really smart. My only question is about the weight. You'd have to be real thoughtful about it.
     
  14. Carlazzomark
    Joined: Oct 2006
    Posts: 103
    Likes: 13, Points: 18, Legacy Rep: 16
    Location: Michigan

    Carlazzomark Senior Member

    If you or anyone else is interested, I will post the specs and partial price sheet that I requested from the company.
     

  15. bajansailor
    Joined: Oct 2007
    Posts: 2,733
    Likes: 1,049, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Yes please, that would be nice.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.