Continuously Variable Transmissions

Discussion in 'Propulsion' started by Fanie, Jul 30, 2009.

  1. Brian@BNE
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    Brian@BNE Senior Member

    Teddy
    The idea is to use as large a diameter as possible, turning relatively slowly. The prop would then be pitched to just give full rpm of engine, as normal. So the issue becomes loss of prop efficiency at lower rpm, also normal.

    When motor-sailing, the CVT would enable the diesel to run, say, just above fast idle, but be loaded enough to operate within an efficient exhaust gas temperature range and hopefully good BSFC.

    I don't know whether fuel savings will give a reasonable payback period for the tranny, but the ambiance in the boat with minimal noise and vibration whilst making good speed when passage-making is one benefit. For a boat that doesn't do many miles it would not be worth considering.

    The other benefit is that on a cat the other hull can have an electric drive, using power from the one running diesel. Its a diesel-electric drive with a difference - one hull is diesel, the other is electric! For redundancy, both hulls will have a diesel, but they can be of different sizes, providing further avenues for fuel efficient passage-making.

    Of course there are issues. Apart from complexity, the CVT tranny could well be heavier than a fixed gear one, and then there is the weight and size of the electric motors and drive controllers etc. Whether it would make sense on a 40-something-ft cat is still to be worked out.
     
  2. TeddyDiver
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    TeddyDiver Gollywobbler

    The weight difference isn't so much an issue with motorsailors and that's about the best possible boat to use with a transmission like this. The limitations with this drive train means that it's at is best when the prop is drived at more or less constant speed just varying the engine rpm depending how much thrust the sails give for the boat.
    BR Teddy
     
  3. brian eiland
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    brian eiland Senior Member

    Sort of something along this idea....
    The power would be a single main engine sized to develop the vessel’s desired top speed, and it could transmit this power by conventional shaft/prop arrangement, or with a azimuthing Volvo IPS dual prop unit, or via a retractable azimuthing Rim-Drive prop unit as I included on my latest dynarig motorsailer design.

    Supplementing this single main engine would be a single DC diesel/electric power unit to provide for:
    1) Ships electrical requirements
    2) Slow speed operation by electric (wing) motor belted to main prop shaft
    3) Maneuvering thrusters as required depending upon azimuth capabilities of main prop.

    The entire ship would be powered by only two engines, basically sized to provide:
    1) Full main diesel power, unimpeded by interceding diesel/electric conversion
    2) Slow speed operation and ship’s systems via the smaller diesel/electric unit
    3) ‘Twin power’ emergency backup as either engine can run all gear
    This configuration more ideally meets the latest thinking for the new diesel/electric DC technologies onboard smaller vessels. Alternatively, two identical diesel/electric plants might be sized such that in combination they would supply the max power required of the vessel, and half power for lesser times.

    Only two engines and no conventional sailing rig should make this a more affordable vessel, both in construction, in maintenance, and in operation. However the SkySail kite arrangement will probably more than offset the conventional sailing rig in cost. Possibly a less expensive alternative to this ‘brand name’, with less computerization could be found (no integrated weather/navigation features, etc). Light-weight construction would be desirable but not necessary. Third world hull construction materials are a possibility.

    I’ll call it a KiteSail Motorsailer for now.
    ....comments, suggestions

    http://www.boatdesign.net/forums/boat-design/new-age-trawler-motorsailer-kite-assisted-poweryacht-20319.html
     
  4. Brian@BNE
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    Brian@BNE Senior Member

    Brian
    Similar concepts for economy and flexibility. But use conventional sailing rig also. Really trying to drive both props in a cat with just one engine, and minimize the inefficiency of small-scale diesel-electric configuration noted by Hybrid-Marine. See their paper, attached, comparing conventional drive, diesel electric and serial or parallel hybrid drives.

    In effect the ideas I put above is the Hybrid-Marine set-up, but with something like the NSK toroidal variator instead of their fixed ratio PRM 150 gearbox. The variator is a key part of the overall system efficiency for a cat installation.
     

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  5. Boston

    Boston Previous Member

    next question is cost

    whats it cost to gain what in efficiency

    and whats that translate to in fuel savings and how long does that take to pay itself back compared to the added complexity and weight of the hybrid system?

    on that 35 I'm playing with two new Kubota engines cost 4200 each, and two multiple v belt reduction arrangements + 2 clutchs seems so much cheaper than all the hybrid stuff you'd have to put in 10xthousands of miles a year to hit pay back time.
     
  6. Brian@BNE
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    Brian@BNE Senior Member

    Boston
    yes, cost will be an issue. I'm not into VW at 40k either. I wouldn't want to think what they cost in AU if that's the price you can get. And the Hybrid-Marine prices are scary for their electric stuff, and to boot they are in GBP.

    Not sure what Catbuilder came up with as far as final config and costs were for his electric options. That thread of his went cold a bit after he clammed up thinking he'd invented a retractable drive or something, but wouldn't share it on the forum.

    I've emailed NSK for dimensions, weight and input power range for their new toroidal variator. No doubt they'll need a significant car manufacturer to sign up before the things are commercially available, and only then would talking to them on cost make sense.

    So yes, I'm probably dreaming with the stuff I've put here. A bit like your pencil/eraser story on your 35ft design. By the way, just buy something the right length, cut off the superstructure and put yours on. Bound to be cheaper. My guess is used boats are 30 cents in the dollar compared to new build right now.

    I'm OK with your 'junkyard wars' approach , but would want a system that provided reverse quickly and reliably. V belts would be OK with a CPP, but so far I can't find any CPP's in the size we'd be using (40-46ft sailing cat to be re-powered in my case). To me the 'junkyards' worth fossicking in are the farming/agricultural ones. Sure they use v belts in some gear, but there is a lot of other stuff at right power ratings that might be able to be used differently to original purpose. Cost and efficiency are words that mean a lot to those folks too.
     
  7. Boston

    Boston Previous Member

    go to any agy supply and look at PTO shaft accessories, a dime a dozen and all well within the 40 hp and 100 ft/lb range we'd be needing. They got some real nifty stuff and its all continuous duty. You can find the stuff used by the tens of thousands.
     
  8. whitepointer23

    whitepointer23 Previous Member

    the nissan merano is a large vehicle with a powerfull engine driving a cvt.
     
  9. BATAAN
    Joined: Apr 2010
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    BATAAN Senior Member

    I've been pushing water with a controllable pitch SABB 30 hp for many years and would feel very handicapped going to a fixed pitch prop. When approaching a dock in the wind with my 40', 23 ton yawl, I reduce pitch but not RPM until we are just crawling along, but still under control. Usually I can lay the boat alongside and just drop the lines on the cleats from the deck. Also, at sea when motorsailing or motoring, the load is always properly adjusted by pitch and throttle. This setup seems to be exclusively a European thing, like medical care and parental leave, so I won't hold my breath to see it built or used here, too sensible.
     
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  10. jak3b
    Joined: Apr 2011
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    jak3b Junior Member

    Hey,This is Amuraka it doesnt have to make sense just money.
     
  11. Brian@BNE
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    Brian@BNE Senior Member

    Someone who can supply CPP in the 50-200 HP range would really make money.....
     
  12. BATAAN
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    BATAAN Senior Member

    Some current manufacturers of CP systems.
    The rest of the world is leaving us behind.
    No surprise since we're headed back to the 1880s as fast as we can go. Screamingly afraid of the future and science is the way we are viewed by people in other countries.
    I have friends in Europe and a brother-in-law in China and hear a lot about how dense we are and unwilling to do anything sensible.
     

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  13. TeddyDiver
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    TeddyDiver Gollywobbler

  14. Brian@BNE
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    Brian@BNE Senior Member

    Thanks Teddy, some good links there.
    1. Cant find any sizes for Nogva
    2. Westmekan give a range of dimensions, except prop diameter but from shaft size etc it looks as though their sailing CPP range could be in the right size!
    3. Selfa appear to carry/supply from a range of manufacturers, possibly some are in the low power/sailing boat range
     

  15. Brian@BNE
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    Brian@BNE Senior Member

    Hmm, interesting. Finnoy only shown down to 1000 mm size, P26. But Marine Systems (UK) Ltd, who source from Finnoy, show a P18 down to 650 mm. This could well be just the right size!

    Once I have got the boat and can advise the required input details, a quote from these folks could be the way to go. No doubt I'd want to be sitting down when i got their reply, but still......
     
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