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"The power is generally applied by a wheel or a lever, and moves through the circumfrence of a circle. The distance between the two consecutive turns of any on continuous thread, measured in the direction of the axis of the screw, is called the pitch of the screw." -Avery 1895

Screw with Lever Arm

"The power is generally applied by a wheel or a lever, and moves through the circumfrence of a circle.…

Compound screws commonly used as clamps.

Compound Screw

Compound screws commonly used as clamps.

A lever of the second class

Second Class Lever

A lever of the second class

"A lever is an inflexible bar freely movable about a fixed axis called the fulcrum. If the weight is between the power and the fulcrum, the lever is of the second class." — Avery, 1895

Second Class Lever

"A lever is an inflexible bar freely movable about a fixed axis called the fulcrum. If the weight is…

"The second kind of lever is represented where W is the weight, L the lever, F the fulcrum, and P a pulley, over which a string is thrown, and a weight suspeneded, as the power." -Comstock 1850

Second-class Lever

"The second kind of lever is represented where W is the weight, L the lever, F the fulcrum, and P a…

"Two men carrying a load between them on a pole is also and example of this [second class] kind of lever. Each man acts as the power in moving the weight, and at the same time each becomes the fulcrum in respect to the other." -Comstock 1850

Second-class Lever

"Two men carrying a load between them on a pole is also and example of this [second class] kind of lever.…

"Second class lever." -Comstock 1850

Second-class lever

"Second class lever." -Comstock 1850

"A Lever of the Second Kind is one in which the weight is between the power and the fulcrum." —Quackenbos 1859

Second Class Lever

"A Lever of the Second Kind is one in which the weight is between the power and the fulcrum." —Quackenbos…

In the second order of levers, the weight is between the power and the fulcrum.

Second Order of Lever

In the second order of levers, the weight is between the power and the fulcrum.

"A pracitcal application of a balance/lever is a see-saw." —Quackenbos 1859

See-saw

"A pracitcal application of a balance/lever is a see-saw." —Quackenbos 1859

"Railway Semaphore. a, lever, which operates both b, blade, and c, lantern." -Whitney, 1911

Railroad Semaphore

"Railway Semaphore. a, lever, which operates both b, blade, and c, lantern." -Whitney, 1911

"Singer sewing-machine. a is the frame and cloth-plate or bed-plate; b, arm; c, treadle; e, pitman; d, main driving-wheel; f, band; g, small driving-wheel attached to shaft ... j, take-up lever with roller and stud; k, presser-bar carrying presser-foot; l, needle-bar; m, spool-pin; ... t, drawers." -Whitney, 1911

Singer Sewing Machine

"Singer sewing-machine. a is the frame and cloth-plate or bed-plate; b, arm; c, treadle; e, pitman;…

"A contrivance extensively employed in Egypt and the East, generally for raising water. It consists of a long stout rod suspended on a frame at about one fifth of its length from the end. The short end is weighted so as to serve as the counterpoise of a lever, and from the long end a bucket is suspended by a rope. The shadoof is extensively used in Egypt for lifting water from the Nile for irrigation" &mdash;Whitney, 1889 <p>This illustration shows two men using a shadoof to raise water. There is a sailboat in the background.

Shadoofs, Two Men Raising Water

"A contrivance extensively employed in Egypt and the East, generally for raising water. It consists…

"Any rod, or bar, which is used in raising a weight, or surmounting a resistance, by being placed on a fulcrum, or prop, becomes a lever." -Comstock 1850

Simple Lever

"Any rod, or bar, which is used in raising a weight, or surmounting a resistance, by being placed on…

"Suppose that A is the lever, B the fulcrum, D the weight to be raised, and C the power. Let D by considered three times as heavy as C, and the fulcrum three times as far from C as it is from D; then the weight and power will exactly balance each other out." -Comstock 1850

Simple lever system

"Suppose that A is the lever, B the fulcrum, D the weight to be raised, and C the power. Let D by considered…

"Suppose the weight, B to be sixteen pounds and suppose the fulrum to be placed so near it, as to be raised by the power A, of four pounds hanging equally distant from the fulcrum and the end of the lever. If now the power A be removed, and another of two pounds, C, be placed at te end of the lever, its force will be just equal to A, placed at the middle of the lever." -Comstock 1850

Simple Lever System

"Suppose the weight, B to be sixteen pounds and suppose the fulrum to be placed so near it, as to be…

"But let the fulcrum be moved along to the middle of the lever, with the weight of sixteen pounds still suspended to it, it would then take another weight of sixteen pounds, instead of two pounds, to balance it..." -Comstock 1850

Simple Lever System

"But let the fulcrum be moved along to the middle of the lever, with the weight of sixteen pounds still…

Illustrations showing the six mechanical powers: lever, wheel and axle, pulley, inclined plane, wedge, and screw.

Simple Machines

Illustrations showing the six mechanical powers: lever, wheel and axle, pulley, inclined plane, wedge,…

A form of spring safety-valve, in which a series of bent springs h h h are placed alternately in opposite directions, their extremities sliding upon the rod i, and the springs being kept down by the crossbar k; a being the valve, c the valve-seat, and b b part of the boiler.

Lever Spring Safety-valve

A form of spring safety-valve, in which a series of bent springs h h h are placed alternately in opposite…

An illustration of Newcomen atmospheric steam engine. The boiler heats the water to build up steam in the piston. While the steam lever closes, the water is let in, and the piston compresses the steam to generate energy. The compressed steam turns to liquid, and opens the steam valve.

Newcomen Atmospheric Steam Engine

An illustration of Newcomen atmospheric steam engine. The boiler heats the water to build up steam in…

The illustration showing Watt's final steam engine design. The engine is fitted with series of rods to guide the in a straight line. James Watt and William Murdoch invented the throttle valve, centrifugal valve, regulator, and slide valve to improve on the steam engine.

Watt's Final Steam Engine Design

The illustration showing Watt's final steam engine design. The engine is fitted with series of rods…

"The Steelyard is more portable then the ordinary balance. It consists of a lever, AB, moving round a knife-edge or point at C. The body to be weighed, W, is put into the scale which hangs from A; and a movable weight P, is made to slide along the longer arm, until the lever, AB, remains horizontal." &mdash; Chambers' Encyclopedia, 1875

Steelyard

"The Steelyard is more portable then the ordinary balance. It consists of a lever, AB, moving round…

"When bodies of unequal weight are supported by the arms of a lever, they will balance each other whenever the weight of the one multiplied into its distance from the fulcrum." &mdash;Quackenbos 1859

Steelyard

"When bodies of unequal weight are supported by the arms of a lever, they will balance each other whenever…

"The steelyard is a kind of balance, which, though not so sensitive as the one being described above, answers very well for heavy bodies, and is conveniently carried, as it requires but a single weight, and may be held in the hand or suspended anywhere." &mdash;Quackenbos 1859

Steelyard

"The steelyard is a kind of balance, which, though not so sensitive as the one being described above,…

A suction-pump with the upward and downward movement of the piston being effected by means of a lever.

Suction-pump

A suction-pump with the upward and downward movement of the piston being effected by means of a lever.

"System of Wheels.&mdash;As the wheel and axle is only a modification of the simple lever, so a system of wheels acting on each other, and transmitting the power to the resistance, is only another form of the compound lever. The first wheel a, by means of the teeth, or cogs, around its axle, moved the second wheel, b, with a force equal to that of a lever, the long arm of which extends from the center to the circumference of the wheel, where the power p is suspended, and the short arm from the same center to the ends of the cogs. The dotted line c, passing through the center of the wheel a, shows the position of the lever, as the wheel now stands." &mdash;Comstock, 1850

System of Wheels

"System of Wheels.—As the wheel and axle is only a modification of the simple lever, so a system…

A lever of the third class

Third Class Lever

A lever of the third class

"A lever is an inflexible bar freely movable about a fixed axis called the fulcrum. If the power is between the weight and the fulcrum the lever is of the third class." &mdash; Avery, 1895

Third class lever

"A lever is an inflexible bar freely movable about a fixed axis called the fulcrum. If the power is…

"In the third and last kind of lever, the weight is placed at one end, the fulcrum at the other end and the power between them, or the hand s between the fulcrum and the weight." -Comstock 1850

Third-class Lever

"In the third and last kind of lever, the weight is placed at one end, the fulcrum at the other end…

"Third class lever." -Comstock 1850

Third Class Lever

"Third class lever." -Comstock 1850

"A Lever of the Third Kind is one in which the power is between the weight and the fulcrum." &mdash;Quackenbos 1859

Third Class Lever

"A Lever of the Third Kind is one in which the power is between the weight and the fulcrum." —Quackenbos…

In the third order of levers, the power is between the weight and the fulcrum.

Third Order of Lever

In the third order of levers, the power is between the weight and the fulcrum.

An illustration of a lever safety valve. "Suppose the valve A is just suppose to open when the steam pressure under it is 120 lb. per square inch, that mean area of the valve exposed to steam pressure is 4 square inches, the weight of the valve 4ln., the distance C D being 3 inches the centre of gravity of the lever 7 inches from D, and its weight 6 lb.; where must the weight E - which is 50 lb. - be placed on the lever? The total upward force on the valve is 120 &times; 4 - 4 = 476 lb., and the moment of this force about D is 476 &times; 3 = 1428. This is the only negative moment, all other forces tending to turn the lever the opposite way." -New, 1891

Lever Safety Valve

An illustration of a lever safety valve. "Suppose the valve A is just suppose to open when the steam…

"The wheel and axle consists of a wheel united to a cylinder in such a way that they may turn together on a common axis. It is a modified lever of the first or second class." &mdash; Avery, 1895

Wheel and axle

"The wheel and axle consists of a wheel united to a cylinder in such a way that they may turn together…

"This figure represents the machine endwise, so as to show in what manner the lever operates. The two weights hanging in opposition to each other, the one on the wheel at a, and the other on the axle at b, act in the same manner as if they were conected by the horizontal lever a b, passing from one to the other, having the common centre, c, as a fulcrum between them." -Comstock 1850

Wheel and Axle

"This figure represents the machine endwise, so as to show in what manner the lever operates. The two…

"The wheel and axle consists of a wheel united to a cylinder in such a way that they may turn together on a common axis. It is a modified lever of the first or second class." -Avery 1895

Wheel and Axle with Rope and Bucket

"The wheel and axle consists of a wheel united to a cylinder in such a way that they may turn together…

"Considered as a lever, the fulcrum is at the common axis, while the arms of the lever are the radii of the wheel and of the axle. The usual arrangement is to take ac, the radius of the wheel, as the power arm, and bc , the radius of the axle, as the weight arm." -Avery 1895

Wheel and Axle

"Considered as a lever, the fulcrum is at the common axis, while the arms of the lever are the radii…

A wheel with pointed and angular teeth, against which a ratchet abuts, used either for converting a reciprocating into a rotatory motion on the shaft to which it is fixed, or for admitting of circular motion in one direction only, as in a winch.

Ratchet Wheel

A wheel with pointed and angular teeth, against which a ratchet abuts, used either for converting a…