Surface Propulsion, long-tail-emprovements.

Discussion in 'Surface Drives' started by tom kane, Feb 9, 2016.

  1. mydauphin
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    mydauphin Senior Member

    Yes, there are plenty of U/V and CV systems around. Heck you can go to a loc al shop that works on car and they work something up for you on a old car drive shaft. The problem is you need an inexpensive thrust bearing block before you set up the flexible part.

    Every drive system has to have one. Outboard motors have next to the prop. Arneson's have at the just inside the boat on the tail. But if you rig up your own system you have to make one. The bearing themselves are not that expensive, but the machining is tricky. You need two sets, one for forward and one for reverse.
     
  2. tom kane
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    tom kane Senior Member

    Surface Propulsion,long-tail-emprovements

    I have always used a thrust bearing on the prop shaft and one is shown in the image posted.
    In that case the thrust bearing which is available for big industrial use also acts as the pivot point for a Pivotal Drive and is already made in standard form,no problem at all. You could invent new design maybe.
    There are lots of ways you can build a retractable shaft drive just takes some thought, there are plenty of examples around for the armature and a more expensive build.
    You can build them for poorer countries out of less expensive materials and less complicated with practically no maintenance.
    And build them for the more glamours and wealthy market.
     
  3. tom kane
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    tom kane Senior Member

    Surface Propulsion,long-tail-emprovements

    Take a look at the restrictions on stern drive and their mechanical complexities
    and all other systems.
    Everything has limits but they are still driven beyond recommendations.
     
  4. tom kane
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    tom kane Senior Member

    Surface Propulsion, long-tail-emprovements

    There are many ways to build a Retractable shaft drive from many components but preferable modern design. you can use the grey shaded components as in diagram.

    A steerable and retractable AND jack able one may suit you better.
     

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  5. brian eiland
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    brian eiland Senior Member

    Belt Drives, specificately silent chain types

    http://www.boatdesign.net/forums/inboards/belt-drive-37290-3.html#post453264

    At one point I had posted a fair amount of info, and some photos on these types. But a number of the links and sites are no longer any good.

    Had thought that one variation might have the 'outdrive leg' pivot up out of the water around that upper drive pulley/gear.

    And here I suggest a duo-prop arrangement:
    http://www.thehulltruth.com/8495329-post208.html

    http://www.runningtideyachts.com/dynarig/Tennant_Hull_V_ChainDrive.php
     
  6. powerabout
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    powerabout Senior Member

    Mercruiser early II drive swivelled around the top input shaft
    Had a handle on the inside to wind it around
     
  7. mydauphin
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    mydauphin Senior Member

    I don't think this will work for a large boat with big props. Every thrust bearing system I look at for my setup cost as much as my engines. Presently the 3 inch shafts go straight to my tranny, the angle is not perfect and I want to reduce a bit of vibration and put softer engine mounts, and a jack shaft. So looking at building then from roller bearings but this is not inexpensive either.
     
  8. tom kane
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    tom kane Senior Member

    You should be able to use heavy industrial twin U/V`s with a sliding spline and a thrust bearing as they are available up to at least 4 inch shafts to connect to your trans and use soft rubber mounts on your engines.
    Trying to keep a propeller shaft aligned vibration free without some form of free movement is just about impossible. This could possibly do away with the need for a jack shaft.
     
  9. tom kane
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    tom kane Senior Member

  10. powerabout
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    powerabout Senior Member

    Reverse is where they perform the worst of any drive system.
    Its their achillies heal thats for sure.
     
  11. tom kane
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    tom kane Senior Member

    If you have a propeller that works equally well in reverse as forward how does that apply?
    But you will not get that with a screw propeller.
    Some mud drives have manual reverse of sorts.
     
  12. powerabout
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    powerabout Senior Member

    because the water that comes off the propeller in reverse hits the transom instead of going under the boat, if you trim it out like a high mounted sterndrive to direct it under the boat your prop is all but out of the water.
     
  13. tom kane
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    tom kane Senior Member

    Surface Propulsion,long-tail-emprovements

    I doubt if that theory holds any water.
    With a fully submerged prop (which you can achieve with an adjustable shaft stern drive and a long tail) the water coming from a prop is sufficient to propel a boat at a reasonable thrust and speed in reverse, if a suitable gear ration is chosen and a suitable prop with the right blade area to move your boat at the speeds you need.
    Fixed surface drives would have that problem and inboard /out boards tilting in shallower water at launching, also outboards.
     
  14. powerabout
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    powerabout Senior Member

    its not theory its driving them and watching them move in a marina and I'm sure its one of the main reasons for their lack of take up on production boats
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    powerabout seems very cluey to me, Tom, take note of what he says ! The problem of drive angle and boat trim is another thing that could cause vexation. When something comes along that seems to have advantages, but does not really take much share of the market, there must be a significant downside.
     
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