Hybrid transmission for planing craft

Discussion in 'Hybrid' started by Magnus W, Jan 12, 2019.

  1. Magnus W
    Joined: Nov 2017
    Posts: 147
    Likes: 13, Points: 18
    Location: Sweden

    Magnus W Senior Member

    I'm trying to find a transmission, a complete hybrid solution or a plain trans with PTI, for the boat I'm going to build.

    My intent is to have a diesel main engine for high speed and an electric low speed engine to drive the jet (or prop) at speeds well below hull speed.

    So far I've struck out trying to find a transmission with PTI that's light enough for my boat or an add on solution that's, once again, light enough. Seems like hybrid transmissions are either for small displacement craft with small IC engines or for larger displacement vessels (ie mega heavy).

    Transfluid have solutions that you put between the engine and trans but the unit they have that's rated to handle my IC input torque weighs close to 600 kg and requires some 750 mm space length wise – not an option.

    I've also been in contact with Katsa in Finland but so far I haven't heard from them.

    My diesel is rated at 442 kW at 2400 rpm. In the best of worlds I can get by with a 15 kW electric but I'm shooting for a 35-40 kW unit.

    Also, I'm not designing this to be a parallel system but it's rather a diesel OR electric. Nor do I need to charge the batteries with the diesel (not that I mind the option should it come "free").

    Any thoughts on where to turn?
  2. philSweet
    Joined: May 2008
    Posts: 2,635
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Unfortunately, the easiest way to do this tops out at about 300 hp at 2800 rpm. The ZF 115 IVTS is the beefiest hollow through-shaft design I've found so far. Just bolt a sheave to the coupler and belt to the hybrid system. Consult tech services for allowable overhang loads. But for what you are asking for, I doubt it would need anything special.

  3. Barry
    Joined: Mar 2002
    Posts: 1,812
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    Barry Senior Member

    You have not exactly stated why you want the electric option.
    If it is for a get home option, perhaps you could design an electric wing motor. Certainly another shaft seal but these seals have been proven over time. Additionally, you can match the prop
    to the input horsepower rather than just have a much smaller electric motor turn a prop designed for 10 times the power, which might not be effective for slower speeds.
    A feathering prop would reduce drag. This system might be a very lightweight and cheaper alternative to a transmission and hook up to same.
    If a get home engine is the requirement, a swim grid mounted outboard. $5000 US gets you a high thrust 25 hp. This will run for hours on minimal fuel, ie no expensive batteries

  4. Magnus W
    Joined: Nov 2017
    Posts: 147
    Likes: 13, Points: 18
    Location: Sweden

    Magnus W Senior Member

    Electric for business reasons. For all other reasons I agree with you.
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