What are all these different types of bearings?

Dear Car Talk

Dear Car Talk | Nov 01, 1996

Dear Tom and Ray:

I have a question that I need your help with. No one else has ever given me
a satisfactory answer. If an engine is said to have five "main" bearings,
does that mean the bearings in question are: 1) the PRIMARY support
bearings, as opposed to the secondary bearings? 2) drilled to provide a
flow of oil to lubricate the piston rods (in the manner of "water mains")?
3) a combination of 1) and 2)? or 4) the term has no meaning at all. I am
truly perplexed. -- Gerry

TOM: Don't feel bad, Gerry. My brother feels that way every time a car
comes into the shop.

RAY: The "main bearings" are like the "main man." They're "it." They're

TOM: The main bearings are the primary, central bearings in the engine. And
they perform a crucial function; to hold the crankshaft to the engine
block, and allow it to spin. And the more main bearings in the engine, the
better, because that crankshaft has to withstand the tremendous forces
created when the "explosions" take place in the cylinders.

RAY: The term "main" also distinguishes them from the connecting rod
bearings, which -- while slightly less central -- -do the equally important
job of linking the crankshaft to the connecting rods.

TOM: And it just so happens that oil does pass through the main bearings
(sort of like your "water main" example) and then goes through crankshaft
to lubricate those connecting rod bearings.

RAY: But does this function have any bearing on the term "main bearings?"
Not to my knowledge. But next time I run into Mario or Vinnie Webster
(publishers of Webster's Intercollegiate Automotive Dictionary), I'll ask

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