REVERSE LEVER.
The Reverse Lever is that part of the valve gear connected with the link for raising and lowering it, thereby changing the travel of the valve and reversing the motion of the engine. When the reverse lever is placed in the center notch of quadrant, the lap of slide valve should cover both steam ports, preventing any steam from entering the cylinder, thus stopping the engine. In moving this lever from the center notch, it either drops or raises the link as the case may be, increasing the travel of the valve and allowing steam to enter the cylinder. When the reverse lever is thrown into the outside notch of quadrant at either end you get full travel of the valve which gives full power of engine, providing you have sufficient steam pressure.
ECCENTRICS.
The Eccentric on an engine is for the purpose of moving the valve back and forth upon the valve seat and has a throw equal to the travel of the valve. The throw of eccentric is caused by the wheel or plate being bored to one side of its true center, and generally equals one-half the travel of the valve. If more or less, the difference is caused by the use of rocker arm or similar devices for increasing or diminishing the throw of eccentric as the case may be. The eccentric is accurately fitted and fastened to the main shaft of the engine with set screws or key.
ECCENTRIC STRAP.
The Eccentric Strap is that part of the engine in which the eccentric revolves, and is attached to link by the eccentric rod. It should be kept well oiled to secure a free and easy movement to the link.
On reversing engines there are two eccentrics exactly alike, one connecting with upper end of link, the other with lower end by the eccentric straps and rods. In this case the eccentric rod that is moving the valve is the one nearest to the link block. When the lever is in the center notch the link is also in the center of its travel. In this case, both of the eccentric rods move an equal distance and the link vibrates back and forth, but as the block is in the center it gives no motion to the valve, and as the valve, having sufficient lap, covers both ports when the lever is in this position prevents the ingress of steam to the cylinder, consequently no motion.
ECCENTRIC ROD.
The Eccentric Rod connects the eccentric to the link, two being used on a reversing engine. On a simple engine only one eccentric rod is used and is connected to a rocker arm which is attached to the valve rod.