[SEL] How Babbit Works-will not stick to iron/steel

Richard Allen linstrum55 at yahoo.com
Fri Apr 15 08:33:54 PDT 2005


Rick Strobel’s thread “Wire in main bearing caps”:

Babbit bearing alloys have one property that is both a blessing and a
curse. Babbit contains antimony and occasionally arsenic, bismuth, and
phosphorus as well. These four additives are all members of the “Group
V” family of elements and all share similar properties. One property is
that they will not stick to iron or steel, and a very good example of
this property can be found in the well-known silver solder alloys
called Silphos and Phoscopper used for copper tubing. They work great
on copper but when used on iron or steel they appear to work great, but
on cooling, the phosphorus-containing silver solder falls off! This
property is useful because Silphos and Phoscopper are themselves
fabulous bronze bearing alloys as well, and to cast them a steel
mandrel is machined to size, polished, the phosphorus silver solder
cast around the mandrel, and then the mandrel pressed out. Babbit does
the exact same thing, so to get it to stay inside a steel or cast iron
bearing shell it has the familiar staking holes, screws, wires, and/or
pins that physically “cage” or lock it in place. One recommended
procedure for preparing a shell for casting is to flux it with sal
ammoniac (ammonium chloride) or zinc chloride and tin it with 37% lead
63% tin solder. However, I found out the hard way to NEVER rely on the
tinning to keep the bearing in the shell! The tinning is ONLY to
facilitate the flow of the babbit into the shell so it makes intimate
contact with the backing shell and to prevent air pockets. You must use
staking holes, screws, or the wires that Rick mentioned to keep the
bearing in place. Now, the good part of babbit not sticking to iron or
steel is that particular property is what makes it such a fabulous
bearing alloy! Without antimony or any of the other mentioned
additives, the babbit would gall or smear and become cold soldered to
the cast iron or steel crankshaft bearing surface, with immediate
destruction of the bearing. Besides the traditional antimony content, I
have also worked with babbits that contain arsenic, phosphorus, and
bismuth, which all work very well, with the exception that bismuth
babbit has a maximum operating temperature of about 180°F that
precludes its use in high speed or hot-running engines. Arsenic is
probably the best additive for babbit, but because of the hysteria
associated with it as a violent poison it is nearly impossible to
obtain and its equally deadly “brother” antimony is used instead. Of
course, from over 165 years of excellent service for machine bearings,
the tin-lead-copper-antimony babbit alloys have proven themselves to
100% satisfactory! By the way, until about the year 1839 babbit was
simply called pewter. It was Mr. Isaac Babbit (American inventor,
1799-1862) who improved pewter specifically for use in high performance
marine steam engines. See:

http://www.americanbabbittinc.com/history_of_babbitt_bearings.htm

Work and play safely!


Rich

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