Smaller vessel thrust bearings.

Discussion in 'Propulsion' started by MikeJohns, Jan 29, 2013.

  1. MikeJohns
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    MikeJohns Senior Member

    Does anyone know of off oil bath housings for tapered spherical roller prop shaft thrust bearings or roller thrust bearings for smaller vessels 2.5 tons thrust 800 RPM ballpark.

    I can get a heavy duty plummer block that will take the thrust but only for one bearing/direction I’d like to find an off shelf housing for standard sized bearings .

    I can get an overly large Chinese small ship type tilt pad bearing for around the same price as getting a housing machined locally for two tapered rollers. There’s a market for off the shelf marine thrust bearings in this sort of range. But is any manufacturer filling it , even from China ?
     
  2. michael pierzga
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    michael pierzga Senior Member

    Ive seen small shaft logs on electric launches in the Netherlands. Ill look thru my files to see if I can find them.

    Also try Google..Electric boat Netherlands.

    On the big boats... Rubber Design, Netherlands is a common supplier

    Seatorque ...still looks big for a 2.5 ton.

    http://seatorque.com/boss.asp

    Perhaps your solution may be to shop make the log.
     
  3. MikeJohns
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    MikeJohns Senior Member

    Thanks Michael

    Similarly Aquadrive and Pythondrive.

    I have no problem custom designing one but I was wondering if there was an industrial plummer block style housing arranged for two directional thrust bearings.

    They are available for double row spheroidal rollers which are good for around 30% of their load rating for thrust which might be the easiest option. I think that’s the arrangement Aquadrive and pythondrive have too, Seatorque have no cutaway drawings to show what they do.

    I suppose it's because smaller installations have a thrust bearing in the gearbox but there is a demand. For vessels of 200 tonnes and up there are several ranges of off the shelf bi directional tilting pad type thrust bearings.
     
  4. michael pierzga
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    michael pierzga Senior Member

    The internet is difficult to use...once you loose links its very hard to google and find again. Steam engine boat clubs are a good place to search for simple shafting and thrust bearing solutions.

    Exalto makes oil bath shaft tubes and thrust bearing down to 60mm

    http://www.exalto.com/pdf/ShaftSealing_2010_EN_sealhousings.pdf

    http://www.exalto.com/products.php?id=155591

    http://[​IMG]


    if you make your own tube, the oil seal detail needs thought

    http://www.ocean-venture-seals.com/ECO-SEAL1.htm

    http://www.vulcan-eng.com/workspace...can-brochure-section-7-page-50b74742ae5d0.pdf

    Ive have several service parts blow ups of shaft tubes and Thrust blocks that Ive serviced. They protect their intellectual property by using proprietary part numbers and small scale drawing.

    I can photograph if you need general arrangement .
     
  5. CDK
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    CDK retired engineer

  6. michael pierzga
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    michael pierzga Senior Member

    Grease packed blocks work. Many older boats have grease packed shaft tubes.

    The problem is that people forget to grease them and they burn up. The beauty of the oil bath is its nearly maintenance free and its simple to install a low oil level alarm on the oil header tank
     
  7. MikeJohns
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    MikeJohns Senior Member

    Cornelius, Michael

    Thanks

    I've designed many thrust bearings but always they have been machined to suit.

    And I'd recommend the spherical tapered ( self aligning) bearings rather than the straight tapered roller. Smaller vessels can use a simple flange mount and a single bearing effectively. But by the time you have 2 tonnes of axial thrust or more it's not so simple.

    The 4 bolt heavy duty plummer blocks work but I would have liked to find one that could take 2 bearings and a collar internal to the block, then I can incorporate two tapered bearings and I'd use a few of these in projects.

    The closest I can get to bi directional axial thrust block off the shelf from a bearing supplier seems to be a 4 bolt split plummer block with spherical roller bearings ( not shperical tapered bearings ) with two rows of smaller tapered rollers at a shallow angle, but they will usually take up to 30% of the radial load axially.

    It would be nice to find a commercial bearing housing for two tapered roller bearings and seals. But there are only the high end marketed products mentioned before and they are probably not much better than the spherical roller bearing.

    A robust and off the shelf bearing repalcement would be a better option that proprietory parts . Even though they will use std bearings.

    I was hoping someone had a line to an industrial range of housings.

    The Sketch on the right below shows the setup I'm working on.
    On the left is a true spheroidal self aligning thrust bearing but then two are needed for fwd and astern. In the middle the 2 row spheroidal roller which isn't a thrust bearing but will take around 30% axial load, it will also go in a std plummer block housing so it's a simple solution, but it's using the handle of the sledge hammer to crack the nut. For example for 20kN thrust it needs to be rated for around 70kn radial so all the extra weight is doing nothing useful and not adding to a robust design.
     

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  8. Landlubber
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    Landlubber Senior Member

  9. MikeJohns
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    MikeJohns Senior Member

    John
    I've no problem getting a plummer block there's several bearing suppliers in Hobart with good supplies of SKF FAG Timken ranges but I'll try the easy solution for this job which is the centre pic above.
     
  10. Landlubber
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    Landlubber Senior Member

    OK, no worries.
     
  11. MikeJohns
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    MikeJohns Senior Member

    Ha I'm looking at this now and just following some of the links posted.

    Exalto ... Thanks Michael for that link. (I attached the pdf.)

    one of their off the shelf solutions is just an SKF spheroidal roller bearing in an SKF Plummer block.
     

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  12. pdwiley
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    pdwiley Senior Member

    Mike, I was looking at the SKF 22205 smaller bearings for a similar application. They were used in the BOB drives over in India etc.

    I made a housing for back to back tapered rollers and I'm thinking of swapping it to a single spherical roller bearing simply to minimise the hassle about preload etc. In fact this was on my 'to ask' list as soon as I've got the engine in the boat. Nothing like making things twice (or more).

    As you know I've got some decent sized lathes & mills so if you want to fabricate & machine stuff, you don't need to pay shop rates to do it. You can use my big Monarch if the job wouldn't fit in the Colchester.

    I have a number of oddball spherical roller bearings I picked up in Sydney, bore sizes in the 40mm+ range. Feel free to come & take a look.

    PDW
     
  13. MikeJohns
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    MikeJohns Senior Member

    Hi Peter
    I'll check Exalto's suggested sizes but I'd say they have done the homework with SKF. Funny that they should clearly identify the off the shelf parts direct from SKF.

    And for your boat you can use a flange mount on a web. If you give me your Engine data, prop dims and g box reduction via email I'll give you the max thrust\bollard pull if you want.

    Thanks for the offer.
     
  14. CDK
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    CDK retired engineer

    In my thrust bearing construction I tried to make the parts as precise as I could, with the neoprene covered simmer ring as a flexible element to obtain zero play.
    Now, several years later and after tightening the cover, I must admit I can feel some play (0.1-0.2 mm) on the port unit, probably caused by a malfunction of the electronic gearshift that allowed the gearbox to engage at several 1000's rpm.
    I contemplated adding a shim, but the splined sleeve around the prop shaft is sort of fused to the shaft, so I will have to live with it.
     
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  15. pdwiley
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    pdwiley Senior Member

    I modelled my thrust bearing assy off the drawing you posted some time ago when I asked, thank you. As far as I can tell without actually using the thing, it'd work fine. It's just that preload that I don't like. It's all very well doing selective assembly and machining the housing, shaft etc to the correct preload tolerance, but I did worry about wear in service and shimming.

    From what you're saying, this is a real issue in practice. The further away from a machine shop you are, the more difficult to deal with. I've got tins of shim stock and could easily make up some, but it's still a PITA.

    If I can swap to a single bearing, this is less hassle down the track, I think, so now is the time to do it. Besides I haven't fitted the engine yet (getting close) so everything is still dead easy to access.

    The UN Bay of Bengal program published a nice little book showing details of tiltable drive systems using the SKF 22205 bearings. Looked simple to do and as my engine is only 36 HP, can't see it being too different.

    PDW
     
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