The crank njikọ mkpanaka usorobụ akụkụ atọ mejupụtara: otu ahụ, piston njikọ mkpanaka na otu crankshaft flywheel. The crank ejikọta mkpanaka usoro bụ isi na-akpụ akpụ akụkụ nke engine na-aghọta na-arụ ọrụ okirikiri ma mezue ike mgbanwe.

N'ime strok ike, ọ na-agbanwe piston ike thermal nke ọkụ ọkụ na-emepụta site na ọkụ ọkụ na-emegharịgharị na ntụgharị crankshaft n'ime ike ọrụ iji mepụta ike; na ọrịa strok ndị ọzọ, ọ dabere na inertia ntụgharị nke crank na flywheel ma na-ebufe piston elu na ala site na njikọ njikọ iji mepụta ọnọdụ maka ọrụ ọzọ.

Ọrụ nke crank na-ejikọta mkpanaka usoro bụ inye ebe maka combustion, na-agbanwe nrụgide mgbasawanye nke gas n'elu piston mgbe mmanụ ọkụ na-ere ọkụ n'ime ụda nke ntụgharị crankshaft, na-aga n'ihu na-arụpụta ike.

(1) Gbanwee nrụgide nke gas n'ime torque nke crankshaft;

(2) Gbanwee mmegharị mmegharị nke piston n'ime ntụgharị ntụgharị nke crankshaft;

(3) Gbanwee ike nke combustion na piston n'elu n'ime torque nke crankshaft iji mepụta ike n'ibu na igwe na-arụ ọrụ.