Big end bearings (Three bearing engine)

[Hugh Sammons]

I am dismantling and cleaning a three bearing engine crank case.
The big end bearings are as shown in the photograph. Why are they less wide than the connecting rod housing into which they fit? 
Are they perhaps incorrect shells?

Many thanks,
Hugh

[Zetomagneto]

That's how they are. Look at any shell bearing in a conrod and you will find them to be the same.

[Chris KC]

So that they clear the fillet radius on the end of the crankpin.

I have no idea how present supplies (ex-Reliant I think) compare with original Austin shells but they are generously sized compared with modern big ends.

[Zetomagneto]

Correct Chris

[Bob Culver]

Shells in modern cars appear incredibly meagre for the whopping and sustained cylinder pressures and rev capability. The fancy thin layered materials running on hardend shaft, with pressure lube,  withsatnd in psi several times thick white metal.

[AustinWood]

Thin wall shells alow much better cooling of the bearing surface.

[Hugh Sammons]

Many thanks for your comments.
Hugh

[Zetomagneto]

Austin, I always thought the oil cools the bearing as it is constantly passing through.

[Colin Reed]

HI ALL,
One of the reasons for bluing shell bearings when fitting is to make sure that there is full contact between the rod and shell to transfer heat other wise you are libel to melt the shell material at that point.

Colin 
NZ

[andrew34ruby]

Where does the heat come from? Presumably the oil is heated as it cools the bore and piston. Without some form of cooling is there really enough friction in the big end bearing to create a problem with high temperatures?