shaft bearings ideas please

Discussion in 'Metal Boat Building' started by Guest62110524, Jun 21, 2009.

  1. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    Sorry Stu missed that, something wrong with your calculator :)

    (40^2)^(0.333.) X 0,142
    =(1.6E3)^(0.333.) X 0.142
    =11.70 X 0.142
    =1.66 m
     
  2. Guest62110524

    Guest62110524 Previous Member

    S,all right fer you, but sci fi calculaters, I can not drive
    Ah well, I have 1.6, from inboard end of bearing
    I will stick number 8 coupling as for 12 would need spacer to clear pump,
    Oh Fer your info
    I ordered sections from China price to you::)) 5 dollars kg
    It took a long time to est. trust with them but after ringing their clientele around the world I am satisfied
     
    Last edited: Jun 21, 2010
  3. Brent Swain
    Joined: Mar 2002
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    Location: British Columbia

    Brent Swain Member

    Bearings and couplers

    20 years ago I machined a plastic drivesaver type coupling insert out of a piece of 3/4 inch poly plastic cutting board type material, and it is still there ,no problems, after cruising 11 months a year since. With the insert on one side and the projection to fit into the tranny on the other, it stays completely centred. Using my angle grinder for a lathe, I made several spares, but haven't had to use any.
    I once used a poly plastic hose barb for a shaft bearing , on a direct drive , 2500 shaft RPM ,for three years with no visible wear. I've been told big ships use gumwood for shaft bearings. One couldn't ask for better lube or cooling than at the back of the stern tube.
    Brent
     
  4. apex1

    apex1 Guest

    Stu, what are those sections? Precut ally or prefabricated (welded) structure?

    Regards
    Richard
     
  5. Guest62110524

    Guest62110524 Previous Member

    one is solid railcap, the other is 16mm face belting
    this company has clients all aroung the world, they built the dies for only 2200 US, and I only ordered 780kgs, enough 2 boats
    the railcap is the ideal way to top a bulwark, both 6082 T6
    CAN YOU READ RHINO FILES YET? OR DFX?
     
    Last edited: Jun 21, 2010
  6. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    Ships have use a variety of synthetic materials for decades now that out-perform the lignumvitae and similar oily hardwoods.

    Couplings come in all shapes and sizes in industrial applications and I 've seen some very good home-brew affairs. They are much simpler and under considerably lower combined loads if a thrust bearing is fitted on the shaft.

    I should also mention the other advantage of a thrust bearing when the engine is soft mounted, it prevents the fore-n-aft movement of the engine under load.
    A common problem is insufficiant clearance between the prop and the cutlass bearing. It's not uncommon for the compression of the rubbers in the mounts and the coupling to cause the prop to slide foreward by half an inch ubder load. Then you see the characteristic wear rings on the hub, also it seals of the cutlass tube the end of which becomes a thrust bearing.

    This movement can aslo screw up close tolerance minimum spacings to deadwood etc with higher vibration at higher power making people scratch their heads.

    This foreward movement can also do nasty things to that nice computer shaft alignment :)
     
  7. Guest62110524

    Guest62110524 Previous Member

    Yes nice post mike
    these days one must shop around, take into account labour times vs store bought
    many of the later (softmts) are desined to take the thrust with min distortion fore and aft
    I do prefer the Aquadrive, COS it does have a big thrust bearing, which one must mount upon the hull structure All very easy on a metal boat, but just another big exercise on a glass or timber boat when machines for fabricationg steel and al al are not to hand,
    Nice day up here, heading for 26
     
  8. apex1

    apex1 Guest

    Thanks Stu, nice prices!
    I always could read dxf. dwg and the like. Rhino still not. I haveĀ“nt seen my home since 11month now!! And as it seems to happen I will not for another while.

    Regards
    Richard
     
  9. Guest62110524

    Guest62110524 Previous Member

    to Mike in partic
    you often talk of the movement , thrustwise on (soft mts) but that is nothing compared to when say a yacht drops off a 40 foot wave, or comes to a stop when she hits a solid wall of water, is it?

    Considerable research and developent have gone into making these compounds super reliable, , thrust is nothing compared with such as I just described, or knockdown or even a total 360 rollover, is it?
     
  10. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    The compounds are excellent now, much better than 20 years ago, just the metal is often only electroplated and needs painting :)

    It's an interesting exercise to measure just how much the engine throws off with full power, most people never think of this. On some big powerful soft mounted installations there is an arm to reduce it but never on the smaller installations.

    Hog and sag and wracking in a seaway are all factors in any boat for shaft alignment. How much it moves depends on the vessels design and construction.

    A lot of steel vessels are quite stiff in the engine and shaft area and with well designed installation ( engine beds,decent central keel etc) you don't find that much flex from hull movement.

    In contrast some light weight FRP vessels afloat at the dock, just a person walking fwd on deck can pinch the feeler gauge when doing a shaft alignment.

    Larger Trad timber fishing boats bend like anything in a seaway but often massive engine beds and a rock crusher bolted hard down keep them quite rigid one way or another and then I'm never quite sure just what is supporting what.

    Added a pic of trad timber fisherman which shows the Bulwark buckling as they encounter a head sea.
     

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  11. Guest62110524

    Guest62110524 Previous Member

    likewise al al, no movement, fishing boats on the Au coast often have = paravane flopper stoppers, they are really hard on a timber boat
    what are rental propertys like down there? cheaper? more available?
     

  12. Brent Swain
    Joined: Mar 2002
    Posts: 951
    Likes: 35, Points: 0, Legacy Rep: -12
    Location: British Columbia

    Brent Swain Member

    For the last decade or two I have been using bronze oilite bushings for stern bearings. They work fine, and cost under $5.
    I have seen some very expensive plastic stern bearing advertised, for around 39 cents worth of material and $70 worth of hype.
    Brent
     
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