In a piston engine, the bore (or cylinder bore) is the

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

of each cylinder.

Engine displacement Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as a loose indicator of the ...

is calculated based on bore, stroke length and the number of cylinders:
displacement = The

stroke ratio In a reciprocating piston engine, the stroke ratio, defined by either bore/stroke ratio or stroke/bore ratio, is a term to describe the ratio between cylinder bore diameter and piston stroke length. This can be used for either an internal comb ...

, determined by dividing the bore by the stroke, traditionally indicated whether an engine was designed for power at high engine speeds ( rpm) or

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

at lower engine speeds. The term "bore" can also be applied to the bore of a locomotive cylinder or steam engine pistons.

Steam locomotive

The term bore also applies to the cylinder of a steam locomotive or steam engine.

References

{{Steam engine configurations Engine technology

Steam locomotive

See also

References