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 shell.
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
IMG_3684.jpgIMG_3683.jpg
It makes the edge of the bearing a little floating island above the shell.
(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 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 shell. 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.
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