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  1. #1
    Join Date
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    Default Re-metalling bearings

    Not my work, but I thought folks might be interested in what is involved in replacing white metal bearings.

    This could be the soft metal in a bronze sleeve or shell, or a steel cast or forged cap.
    In this case, engine con rod bearings.


    First, the prep:

    • the old metal is melted out. Big blowtorch. Dribbles out. Just like molten solder.

    • clean the steel thoroughly. In this case, sand blasting and wire brushing.

    • pre-tin the steel. Some people just use flux, but my factory neighbours prefer straight Tin.


    Second, make the mould:
    IMG_3697.jpg
    Bolt a sheet to the flat part, and glue everything together with muffler putty.
    That is to seal it, to prevent the poured metal running out.

    You can't see it in that photo, but there us a half moon shell under there, between the cap and the alloy block.
    Like this one on top:
    IMG_3684.jpgIMG_3683.jpg
    It makes the edge of the bearing a little floating island above the cap.
    (which sometimes becomes the thrust surface that locates the bearing in the middle of the crankshaft)

    Note also this half cylinder, which reduces the amount of white metal they have to pour in there.
    IMG_3699.jpg



    Third, heat up everything:
    IMG_3700.jpgIMG_3685.jpg
    Partly to dry/set the putty, partly to reduce shrinkage of the poured metal.



    Fourth, pour the white metal:
    IMG_3701.jpgIMG_3702.jpg


    Last, cool the metal. The top of the pour forms a skin quite quickly:
    IMG_3688.jpg
    so these guys try to cool the rest from the bottom up, with a little sprayed water.




    The important thing about all this is to test that the bearing is well bonded to the cap/shell/rod.

    You can sometimes see a gap between the white metal and the shell. In bearings that are flush against the casting, the white metal is carefully filed flat, and you can see where the white metal has not bonded.

    Another test is to hit the cap. A well bonded bearing makes a pure ringing sound.



    P.S. White metal is another name for Babbitt metal, name after the guy who invented the alloy.
    Basically any Tin based alloy. Slippery, but hard wearing.
    Last edited by nigelpearson; 13th Dec 2022 at 07:01 AM. Reason: shell->cap

  2. #2
    Join Date
    Jul 2008
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    near Warragul, Victoria
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    Default thanks

    Thanks for posting this.

    I have to do my Morris con rods one of these days .

    I believe the tinning flux is a special flux , I got some from a supplier the other side of Melbourne, I ordered it through the Bunnings special order desk .

    Yes pure tin or close to pure is the best for tinning the bare rods, you use a stainless steel wire brush as you apply the flux and tin and rub the flux in with the brush .

    In my case there are no shells - the bearing alloy adheres directly onto the tinned rods and caps.

    There is some good utube stuff on this topic ..one is by Keith Fenner

    You can line bore the rods in a lathe.

  3. #3
    Join Date
    Jan 2016
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    Wodonga Vic
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    39
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    Default

    Is there any way to get babbitt metal to take to worn aluminium journals? that would be a game changer if it could be done, but I'm guessing it's not possible or people would be doing it to their worn out aluminium cylinder heads

  4. #4
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    Revesby - Sydney Australia
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    Default

    Quote Originally Posted by NedsHead View Post
    Is there any way to get babbitt metal to take to worn aluminium journals?
    I'm not an Alloy expert, but good Aluminium welders can usually re-do the surfaces. I have seen them patch holes in the side of crank cases, build up cylinder heads for extra through studs, and even repair broken machine castings. I think it depends on the type of metal in the casting.


    There are soldering/filler rods that can be blowtorched onto/into Aluminium. I suspect they are too soft for a bearing surface, but these guys claim it is stronger than Aluminium, so who knows!

    https://www.toolking.com.au/aluminiu...ering-welding/

  5. #5
    Join Date
    Oct 2016
    Location
    Melbourne
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    471

    Default

    Quote Originally Posted by nigelpearson View Post
    I'm not an Alloy expert, but good Aluminium welders can usually re-do the surfaces. I have seen them patch holes in the side of crank cases, build up cylinder heads for extra through studs, and even repair broken machine castings. I think it depends on the type of metal in the casting.


    There are soldering/filler rods that can be blowtorched onto/into Aluminium. I suspect they are too soft for a bearing surface, but these guys claim it is stronger than Aluminium, so who knows!

    https://www.toolking.com.au/aluminiu...ering-welding/
    I have been watching some if these vids on welding up aluminium heads https://www.youtube.com/watch?v=h9wKz5xgj-4

  6. #6
    Join Date
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    Default

    I forgot to document one step...

    4.5) After pouring, poke some thin wire or rod down the top, to eliminate any air bubbles




    P.S. The last few bearings these guys did, they did a blow torch on the top
    (to slow it's cooling), instead of spraying the bottom for it to solidify.
    Nigel, from a cave FULL of unfinished projects and lost tools.

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