Chainsaw

Overview

A chainsaw cuts wood with a powered loop of toothed chain that rides around a guide bar. This model is petrol-driven: a single-cylinder, air-cooled two-stroke engine of roughly 50 cc develops power that a centrifugal clutch transmits to the chain only once engine speed rises above idle. The operator controls the tool from isolated handles, and an inertia-triggered brake stops the chain almost instantly if the bar kicks back.

The Engine Assembly is the power unit. Fuel and air mix in a diaphragm carburetor, the charge is drawn through a reed valve into the crankcase, and combustion drives the piston and crankshaft. A flywheel magneto in the ignition system fires the spark plug, and a recoil starter spins the engine to life. When crankshaft speed climbs, the Clutch Assembly engages: its spring-loaded shoes fling outward to grip the drum, and the drive sprocket pulls the chain.

How it works

Cutting is done by the Cutting System. The drive sprocket feeds the Saw Chain, a riveted loop of chisel cutters and drive links, around the laminated Guide Bar. A side-mounted tensioner sets chain slack, and a roller nose sprocket reduces friction at the tip. Because a moving chain runs dry within seconds, the Bar Oiler Assembly meters bar oil from a worm-gear pump onto the bar groove continuously while the engine runs.

Safety and handling are built around the Chain Brake Assembly and the Handle Assembly. A front handguard trips a spring-loaded steel band that clamps the clutch drum on kickback, halting the chain. The wrap-around front handle, pistol-grip rear handle and throttle controls are decoupled from the powerhead by anti-vibration mounts, and a palm-actuated lockout blocks the throttle until the operator has a deliberate grip.