In crankshaft terminology, what is a throw?

• A. The arrangement of two webs together with the connecting rod journal
• B. The distance between the main journals
• C. The surface finish of the crankpin
• D. The space between gear teeth in a gear pair

Answer: (A)

The concept being tested is the offset of the crankpin from the crankshaft’s axis, which is defined as the throw. The throw is the distance from the centerline of the main journals to the centerline of the connecting rod journal (crankpin). This offset is created by the crank webs sandwiching the crankpin, and it determines how far the piston travels as the crank rotates. Twice the throw gives the piston stroke.

Why this is the best fit: the described arrangement of two webs with the crankpin journal directly defines the crankpin’s offset from the shaft center, which is exactly what the throw measures. The other options refer to different dimensions or features—spacing between main journals is a separate measurement, surface finish of the crankpin is unrelated to throw, and gear tooth spacing pertains to gears, not crankshaft terminology.