=The Woolf Valve Gear= is used in connection with an engine to reverse
its motion. It is arranged with one eccentric attached to the crank
shaft the strap of which has a long arm cast on, to which the eccentric
rod that moves the valve is attached. This arm is also supplied with a
roller, which runs in a slot on a rocking head. This head is held in
position by a box and is connected to the reverse lever by a rod. By
throwing the reverse lever to either end of the quadrant, the position
of the rocking head is so placed that the roller in the slide operates
the eccentric strap, rod and valve, and the engine will run in the
direction desired. By throwing the reverse lever to the opposite end of
the quadrant, the position of the rocking head is so changed that it
will reverse the motion of the valve, and the engine will run in the
opposite direction.
[Illustration: Woolf Valve Gear.]
The Quadrant being notched, the point of cut-off can be regulated with
the reverse lever, according to the load; by placing it in the last
notch in quadrant when full power of engine is required, or notching it
up when doing light work, the same as with the link reverse gear.