shaft bearings ideas please

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

  1. Guest62110524

    Guest62110524 Previous Member

    the boat is al al, the shaft is 1 1/2 or maybe 40 2205 which is higher in tensile than 316l and more corrosion resistant
    Plan is pps seal and possible Aquadrive cv in the space available
    It is 2000mm shaft length
    Anybody used the Vetus couplings/ which would be less costly?
     
    Last edited: Jun 21, 2010
  2. apex1

    apex1 Guest

    We use Vetus couplings as standard.
    Regards
    Richard
     
  3. Guest62110524

    Guest62110524 Previous Member

    and alignment are you clock dialing?
     
  4. apex1

    apex1 Guest

    They use a "rotalign" called tool, pretty simple and reliable. Could´nt find out what we paid for it, but was not cheap the Prod. manager remembers. He also said "clock dialing" was the worst method he knows. Except it is done on a calibrated roller bed.
    Regards
    Richard
     
  5. Guest62110524

    Guest62110524 Previous Member

    Another strong point of the Bullflex coupling in the excellent alignment of hte propeller shaft. Perfect alignment of engine and propeller shaft. Perfect alignment of engine and propeller shaft often tends to be a rather time consuming affair, but the Bullflex comes to the aid of the installation engineer. Even with a misalignment of 2 degrees, the shaft will remain perfectly centered onto the flange of the reverse gearbox. On account of a special centering ring, high shaft revolutions are entirely possible and even in reverse gear, the shaft will remain perfectly centered. The non-tapered clamping hub ensures easy installation and - probably even more important: easy dismantling of the shaft assembly. This in contrast with a tapered clamping hum. Costly machining of hte shaft, such as tapering and keyway cutting is not longer required. Just cut the shaft to length, free of burrs, degrease and install.

    i still prefer to clock the coupling(dial indicator) it is best practice, although not a good idea for aquadrive cv types
    oh fisheries supply seattle the bullflex(vetus) 40mm 1000 usa, cheaper than anywhere else
     
  6. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Have similar setup. I am assuming that shaft log is aluminum and that bearings will be composite not bronze. Make sure you have constant water circulation around shaft. Isolate shaft from engine and put plenty of zincs everywhere.

    Aquadrive type is best, but if alignment is less than 2 degrees then bullflex would do but I would try for dead on alignment and let bullflex take care of margin of error. That way bullflex will last longer.

    They are not cheap either...and I have to buy two. I am looking for cheaper alternatives.
     
  7. Guest62110524

    Guest62110524 Previous Member

    yes thanks, me built 32 alloy boats so far:)) so nothing is a mystery and you are right nothing is cheap
    I do not OVERZINC, just dont mix metals Usually Zn in front of prop, and one on keel, thats all ever done I have found Fisheries Supply in Seattle to be cheapest The tube willl be 6080
    if anyone is interested I put a piece material into end, with small hole in centre, one in other end with say 3mm hole, then I stick mig wire through it, , find centre with mig wire, cranked up tight to Centre of bearers or floor or bulkhead, that way you can keep check on alignment whilst welding
     
  8. apex1

    apex1 Guest

  9. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I feel so ancient... I use feeler gauge.
     
  10. Guest62110524

    Guest62110524 Previous Member

    feelers and straight edge are fine, its just I got so used to clock dialing(been around as longs as metal lathes) on my 4 jaw lathe that it became simple
     
  11. mydauphin
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    mydauphin Senior Member

    So we have;
    Lasers
    Mig wire, not sure how that works
    Clock Dialing
    and Feeler gauges

    any other way.
     
  12. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    Stuart et al

    On many smaller boats (<20m) with shaft RPM< 1000 we have been grease filling the tunnels and removing the water lubrication with success and even reduced bearing wear for both the hard rubber and metal bearing surfaces.

    SS shaft corrosion in flooded tunnels, is a pain the water loses it’s oxygen and boats that are laid up for several months suffer from high rates of shaft crevice corrosion . Painting the shafts and tunnels is sensible but often then there is crevice corrosion on the shaft bearing surfaces. Problem boats that we shifted to grease fill are running fine. Then it's sensible to opt for non fluted bearings and grease seals .

    I’d be interested in others experiences here as shaft pitting is a significant problem.

    On smaller vessels unless everything is hard mounted on very rigid beds then shaft coupling alignment is hit and miss with even the most accurate equipment.
    If soft mounted then misalignment is both caused and also accommodated by the mounts, and if you look at how much the engine moves just from torque and main vibration modes and you quickly see that aiming for very high accuracy at the flange faces is invalid. To properly do it you’d crank the engine over to an operating torque angle and do it there :)

    Pull the shaft back into the tunnel so its supported close to the end and a dial gauge will indicate any runout on the flange face and check for any eccentricity on the rim. Check also the gearbox output flange. If anything is out remove and true the faces and surfaces.

    With the shaft back in position you may need to support its weight as the shaft will sag. Recommended procedure is to align the flange edges and then go through the adjustment routine with the engine mounts for the flange gap. At the end it should pinch 3 thickness gauges, strips of paper are quite useful mylar strips are good too and this is easier and more accurate than trying to push a feeler gauge in at 3 points.

    The classic over the top alignment has always been wood and GRP hulls that are a different shape on the hard if not fully blocked, then the alignment should only be done afloat. The engine installer dial gauges the whole installation and if it’s cracked apart in the water the alignment is out by a frightening amount.
     
  13. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I think people in USA are terrified of grease bearings from a environmental fine point of view. It seem to me that shaft pitting is cause by boat siting. If no water circulate around shaft or where bearing and shaft meet it will eat shaft.
    That is why water circulation is crucial even when you are not using boat.
     
    1 person likes this.
  14. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    here are a couple of nice examples of pitting, as noted above.

    One of the main reasons for this, apart that noted, is the material of the stern tube. From our experience, we now always recommend using GRP stern tubes. Have done several with GRP..after many years service...no problems at all...and shaft in excellent condition.
     

    Attached Files:


  15. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    Oil bath is common enough fully sealed and it is easier to seal in grease than oil, how do all the old wooden boats with their greased bronze assemblies get treated in the USA ? Even if the shaft is over-pumped you can have a relief tube into a container inside.


    Interesting AdHoc that the grp tube works this way. how do you fix it within a metal construction such as Stuarts. Do you us it as a tunnel liner?

    In alloy boats we have had more noticable problems with shaft pitting with uncoated tunnels it may be that the alloy surface bonds more of the oxygen from the water and depletes it faster.
     
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