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"It is usual to put the engine on center before setting the valve. First put the engine in a position where the piston has nearly completed the outward stroke, and make a mark M on the guide opposite the corner of the crosshead or at some convenient place." —Derr, 1911

Steam Engine Valve Centered with Piston

"It is usual to put the engine on center before setting the valve. First put the engine in a position…

"When set full gear forward, the valve admits steam to the crank end of the cylinder, and the crank revolves as shown by the arrow. As the crank turns, both eccentrics impart motion to the link, but the "go ahead" link pin H approximately coincides with the link block." —Derr, 1911

Eccentric Motion of the Steam Engine Crank in Full Gear

"When set full gear forward, the valve admits steam to the crank end of the cylinder, and the crank…

"An eccentric on the main shaft gives an oscillating motion to a circular disc called the wrist plate, pivoted at the center of the cylinder. It transmits motion to each of the four valves through adjustable links known as steam rods or exhaust rods, according to whether they move the admission or exhaust valves." —Derr, 1911

Steam Engine with Reynolds Corliss Gear

"An eccentric on the main shaft gives an oscillating motion to a circular disc called the wrist plate,…

"The governor cam rod operates a plate cam having a curved slot so shaped that it takes place of both the knock—off and the safety cam. The steam arm is keyed to the valve spindle and carries at its lower end a steel die which is free to slip up and down a small amount." —Derr, 1911

Steam Engine Brown Releasing Gear

"The governor cam rod operates a plate cam having a curved slot so shaped that it takes place of both…

A Joy valve gear for steam engine rotating the wheel in the direction of the arrow. The lever F changes the direction the wheel would turn when turned to point B.

Joy Steam Engine Valve Gear Rotating Wheel

A Joy valve gear for steam engine rotating the wheel in the direction of the arrow. The lever F changes…

An outline of the Marshall gear from a steam engine. The piston rotates the crank shaft at point H around axis S. The rod F is connected to the bottom rod E. Rod F rotates at axis P to rotate the engine backwards and forward.

Outline of a Steam Engine Marshall Gear Reducing Friction and Wear

An outline of the Marshall gear from a steam engine. The piston rotates the crank shaft at point H around…

"The steam arm is keyed to the valve spindle which passes loosely through a bracket on which the bell—crank lever turns, and the spindle is packed to make a steam—tight joint where it enters the cylinder. Motion of the steam rod toward the right will turn the bell—crank lever and raise the hook stud." —Derr, 1911

Close up of Reynolds Corliss Gear from Steam Engine

"The steam arm is keyed to the valve spindle which passes loosely through a bracket on which the bell—crank…

An illustration of the steam engine with Walschaert gear system on rail tracks. The piston moves the long shaft connected to the wheel. The lever adjusts the rods on top up and the lower ones down to rotate the wheels opposite from the arrows.

Steam Engine with Walschaert Gear on Railroad

An illustration of the steam engine with Walschaert gear system on rail tracks. The piston moves the…

"The main valve controls admission, release, and compression; the other (valve) regulates the cut—off only, which may be changed without in any way affecting the other events of the stroke. This cut—off valve may be placed in a separate valve chest, or it may be placed in the back of the main valve." —Derr, 1911

Close up View of Double Sliding Valve Gears from Steam Engine

"The main valve controls admission, release, and compression; the other (valve) regulates the cut—off…

An illustration of a Corliss steam engine to generate 5000 kW of electricity. The turbines to create electricity is located on the right hand side and the large circular casing in the left. The steam enters the system at a high pressure to turn the turbines.

5000 kW Corliss and Curtis Steam Engine for Electric Generation

An illustration of a Corliss steam engine to generate 5000 kW of electricity. The turbines to create…

"All fly—wheel governors operate by shifting the eccentric either to change the angular advance, the travel of the valve, or both. The principle of a governor arranged to give decreasing lead under the head of governors." —Derr, 1911

Top View of the Fly Wheel Governor Turning Clockwise

"All fly—wheel governors operate by shifting the eccentric either to change the angular advance,…

"As the speed increases, and the link is 'notched up', the lead is increased as the cut—off is shortened, and at high speed we have a large lead. With the Gooch link, the lead can be set for average running speed, and although a little too great for good work at slow speed." —Derr, 1911

Steam Engine Gooch Link and Valve Gear Arrangement

"As the speed increases, and the link is 'notched up', the lead is increased as the cut—off is…

"This occurs in horizontal engines when the valve is set on top of the cylinder instead of on one side. By means of the rocker AG the valve may receive its proper motion." —Derr, 1911

Steam Engine Valve with Lap Connected to Rocker

"This occurs in horizontal engines when the valve is set on top of the cylinder instead of on one side.…

"Since the valve must move a distance equal to the outside lap before admission can take place, it is evident that the eccentric can no longer be at right angles to the crank at the beginning of the stroke, but must be ahead of the right—angle point by an amount equal to AOC." —Derr, 1911

Valve with Lap of Steam Engine at Extreme Left with Exhaust Ports Open

"Since the valve must move a distance equal to the outside lap before admission can take place, it is…

"The relative positions of crank, eccentric and valve when the exhaust closes on the crank end and compression begins. Between these two positions the steam is expanding in the head end and exhausting from the crank end." —Derr, 1911

Steam Engine Valve with Lap Steam Where Slide Valve is Closed

"The relative positions of crank, eccentric and valve when the exhaust closes on the crank end and compression…

"While the crank is moving from the position, steam is being admitted to the head end and being exhausted from the crank end. The inside lap being less than the outside lap, causes the exhaust to continue longer than the admission." —Derr, 1911

Steam Engine Valve with Lap Where Steam is Admitted to the Slide Valve

"While the crank is moving from the position, steam is being admitted to the head end and being exhausted…

An illustration of the valve with lap at the end of the crank end steam compression. The piston will restart the compression cycle of at the head of the piston. As the piston moves, the sliding valve in the top compartment will fill with steam and closes.

Steam Engine Valve with Lap Steam Where Slide Valve is in Open Position

An illustration of the valve with lap at the end of the crank end steam compression. The piston will…

"If the inside lap is increased, the valve must move farther before released occurs and the crank angle would be greater than illustrated. On the return of the valve to the dotted position, the port will close earlier and make an earlier compression. Decreasing inside lap will cause earlier release and later compression." —Derr, 1911

Steam Engine Valve with Lap Steam Where Slide Valve Moved to Open Position

"If the inside lap is increased, the valve must move farther before released occurs and the crank angle…

"This arrangement makes it possible to place the valve and steam chest above the valve motion. A rod from the bell crank lever on the reverse shaft E, leads back to the engineer's cab and connects with the reverse lever." —Derr, 1911

Steam Engine Rocker Arrangement with Valve and Reverse Rod in Eccentric Motion

"This arrangement makes it possible to place the valve and steam chest above the valve motion. A rod…

"The maximum displacement of the valve is attained when the eccentric is horizontal. In this position both the steam and exhaust ports are wide open, and any further motion motion of the piston will cause the valve to move toward its mid position." —Derr, 1911

Valve with Lap of Steam Engine Where Steam Enters the Slide Valve Compartment

"The maximum displacement of the valve is attained when the eccentric is horizontal. In this position…

"The amount that the valve overlaps the steam ports is called the lap of the valve. It will at once be seen that both the admission and exhaust ports may remain closed during a part of the stroke, thus making expansion and compression possible." —Derr, 1911

Slide Valve of Steam Engine

"The amount that the valve overlaps the steam ports is called the lap of the valve. It will at once…

"This valve consists of two pistons connected by a sleeve through which the valve rod passes. This valve rod is prolonged to a small balancing piston, placed directly over the main valve." —Derr, 1911

Cross Sectional View of the High Pressure Cylinder of Piston Valve from USS Massachusetts

"This valve consists of two pistons connected by a sleeve through which the valve rod passes. This valve…