Definition
The distance from the centerline of a crankshaft main journal to the centerline of the crankpin (rod journal). Throw determines the stroke of the piston, which is twice the throw.
Plain English
How far the crankpin is offset from the center of the crankshaft. The bigger the offset, the farther the piston travels up and down inside the cylinder.
Context Anchor
Seen in aircraft engine maintenance when discussing crankshafts, piston stroke, engine dimensions, and overhaul measurements.
Derivation
From the everyday sense of 'throw' meaning how far something is moved or extended. On a crankshaft, it describes how far the rod journal is 'thrown' off-center from the main shaft axis.
Why Pilots Care
Throw sets the stroke of the engine, which directly affects displacement and power output. Maintenance technicians need this concept to understand crankshaft geometry, balance, and inspection limits.
Analogy
Think of a bicycle pedal arm. The pedal is not at the exact center of the crank; it is offset from the center so your foot can make the crank turn. A crankshaft throw is a similar kind of offset inside an engine.
Intuition Check
Do not read throw here as tossing something. In this engine context, throw means a measured offset from the crankshaft centerline.
Example Sentence 1
The crankshaft throw determines how far each piston travels between top and bottom of its stroke.
Example Sentence 2
Excessive wear on the throw journals requires crankshaft replacement before engine reassembly.