Walk-Behind Brush Mower

Overview

A walk-behind brush mower uses a gasoline engine to drive a rotating blade or brush disc, clearing tall grass, thick weeds, and light brush. Unlike rotary lawn mowers that cut grass cleanly, the brush mower works by impact and shear, the spinning bristles or replaceable blade inserts strike vegetation at high speed, breaking and severing stalks. It is rugged and tolerates obstacles (small rocks, sticks) that would damage a conventional blade.

The operator walks behind the machine, steering via the Control Handle and controlling speed with a Throttle Lever. The engine drives the Wheel Assembly through a Gear Transmission, allowing forward, reverse, and speed selection. A separate Blade Engagement Lever engages and disengages the Blade Disc, allowing coasting when not cutting.

How it works

The Gasoline Engine fires on each power stroke of the walk-behind-brush-mower-piston-assembly. The resulting thrust rotates the Crankshaft, which is coupled through a walk-behind-brush-mower-coupling (or direct-drive in some models) to the input shaft of the Gear Transmission.

The transmission is a simple epicyclic or planetary gear stage. One of four or more gear ratios is selected by the operator moving a lever. Each ratio produces a different output speed at the Rear Drive Wheel. Engine throttle is adjusted via the Throttle Lever, which opens the Carburetor butterfly, increasing air and fuel flow and raising engine RPM. At full throttle, the engine holds constant speed via a mechanical governor on the Cylinder Head.

Power is transferred to the rear wheels by either a Drive Belt or gear teeth on the transaxle output shaft. Pressing the Blade Engagement Lever tightens a belt tensioner or engages a centrifugal clutch on the Cutting Shaft. When engaged, the shaft spins at roughly engine speed (reduced by the coupling geometry), rotating the Blade Disc at 1200–2000 RPM. The removable Brush Blade Insert bristles or blades strike vegetation with tremendous force, shattering woody stems and tangled brush. Releasing the blade lever de-tensions the belt, and the disc coasts to a stop as friction drag slows it.

The front wheel(s) are casters, allowing the operator to steer left or right by angling the handle frame.