big end

noun

big end

noun

1

In a piston engine, the larger end (crankshaft end) of the connecting rod that connects a piston to the crankshaft.

From the sound of that motor, I'd say yer big end's gone, mate.
Except in the case of the largest 4-6-2, not yet in contemplation, use of two [outside] cylinders only was decided on for the following reasons:— […] 2. The split inside big end is a source of trouble at high speeds and powers unless exceptional integrity of maintenance can be guaranteed.1951 July, “British Standard Locomotives”, in Railway Magazine, page 441:

1 more example

Oil is carried from the big end to the small end by a centrally drilled oil hole.1958 April 23, “British Railways First Main-Line Diesel-Hydraulic Locomotive”, in Railway Magazine, page 265:

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