Transplant - Bearings

[Dave Williams]

-> Please explain the term "floating rod bearings"......... I've
-> never heard it before...... The only "floating rod bearings" I've
-> experienced are those which spin between the bearing and the
-> rod.......... Definitely a bad deal.... forshadows doom!

 Back in the 1930s many engines used bearings that were cast directly
onto the rod or block surfaces and machined or scraped to size.  The
bearing material was an alloy called Babbitt, (there were actually a
number of different Babbitt alloys) and the resulting bearings were
referred to as "babbitt bearings."

 Cast babbitt bearings were relatively time-consuming to make, so as
labor prices went up they became less cost-effective.  It was also found
that thinner bearings could hold up to load better than thick bearings.
Many engines began using "shell" or "insert" bearings - thin strips of
steel with a thin layer of bearing material - Babbitt alloy,
lead/silver, etc. - cast or laminated in place.  These bearings were
normally a tight fit in their housings; in fact, the OD of the bearing
was usually slightly *larger* than the housing; the difference is called
"crush" and is what keeps the bearing from spinning in the housing.
These types of bearings are in common use today.

 Ford went to an insert bearing on the flathead, but the rod bearings
were strange - they were babbitted on both sides, and floated in between
the crankshaft and rod.  Later they went to conventional interference
fit bearings.  The hot-rodders of the day claimed there was little
difference between the floating and interference bearings.  I've found
no detailed technical information on why Ford chose to do the floating
bearings instead of interference bearings, or why they changed.  I
suspect it had something to do with cost, as the flathead V8 was
rigorously designed down to a price.

==dave.williams at chaos.lrk.ar.us======================================
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