Force and Machines

For many years, people have waged an uphill struggle against the forces of gravity and friction. Fortunately, we now have machines of all kinds to help us along the way. In this wikibook, you will explore different types of machines, find out how they work and discover that the use of simple machines to perform great feats is nothing new.

Get Moving

Friction

Friction is a force that resists the motion of one surfacer past another surface. This force creates a resistance on moving objects and causes them to stop. Wheels or rollers help cut friction between moving, touching surfaces. But you can also use a thick liquid like oil or grease to reduce friction. They are lubricants – substances that reduce friction. Grease forms a smooth layer and makes it easy for an object to slip. Ball bearings are small balls that help cut down on friction inside machines by keeping metal surfaces from rubbing against each other. A bicycle has ball bearings where the wheels are joined to the frame.

However, thanks to friction, the tires do not slip and the bike moves.

Simple Machines

Inclined Planes

Inclined Planes are a type of simple machine useful for raising or lowering a load. An example of a inclined plane is a ramp. A inclined plane allows you to exert less force over a longer distance to achieve a given workload. It looks like a flat, slanted surface.

Lever

Levers are machines consisting of a beam resting on or supported by a point called the fulcrum. Levers allow a large force to be distributed over a small area at one end by exerting a smaller force over a larger area on the other. There are three classes of levers.

• Class 1 - the fulcrum is in the center, between the effort, on one side, and the resistance (load), on the other. Examples include scissors.
• Class 2 - the resistance is in the middle, the effort on one side, and the fulcrum on the other. Examples include a wheelbarrow and bottle opener.
• Class 3 - effort is in the middle, fulcrum is one side, and the resistance is on the other. Examples include tweezers or the human jaw.

Everyday Machines

Scissors

Scissors are hand-operated shearing tools. They consist of a pair of metal blades pivoted so that the sharpened edges slide against each other when the handles (bows) opposite to the pivot are closed. Scissors are used for cutting various thin materials, such as paper, cardboard, metal foil, thin plastic, cloth, rope, and wire. Scissors can also be used to cut hair. Hair-cutting scissors have a specific blade angle ideal for cutting hair. Using the incorrect scissors to cut hair will result in increased damage and or split ends by breaking the hair. Food scissors, also known as kitchen scissors, are for cutting and trimming foods such as meats. Hair-cutting scissors and shears are functionally equivalent, but the larger implements tend to be called shears.

A large variety of scissors and shears exist for different specialized purposes.

Modern scissors are often designed ergonomically with composite thermoplastic and rubber handles which enable the user to exert either a power grip or a precision grip.

Early manufacture: During the Middle Ages and Renaissance, spring scissors were made by heating a bar of iron or steel, then flattening and shaping its ends into blades on an anvil. The center of the bar was heated, bent to form the spring, then cooled and reheated to make it flexible.

The Hangzhou Zhang Xiaoquan Company in Hangzhou, China has been manufacturing scissors since 1663. [3]

William Whiteley & Sons (Sheffield) Ltd. was manufacturing scissors by 1760, although it is believed the business began trading even earlier. The first trade-mark, 332, was granted in 1791.[4] The company is still manufacturing scissors today, and is the oldest company in the West to do so.

Pivoted scissors were not manufactured in large numbers until 1761, when Robert Hinchliffe produced the first pair of modern-day scissors made of hardened and polished cast steel. He lived in Cheney Square, London and was reputed to be the first person who put out a signboard proclaiming himself "fine scissor manufacturer".[5]

During the 19th century, scissors were hand-forged with elaborately decorated handles. They were made by hammering steel on indented surfaces known as bosses to form the blades. The rings in the handles, known as bows, were made by punching a hole in the steel and enlarging it with the pointed end of an anvil.

In 1649, in Swedish-ruled Finland, an ironworks was founded in the village of Fiskars between Helsinki and Turku. In 1830, a new owner started the first cutlery works in Finland, making, among other items, scissors with the Fiskars trademark.

Description and operation: A pair of scissors consists of two pivoted blades. In lower-quality scissors the cutting edges are not particularly sharp; it is primarily the shearing action between the two blades that cuts the material. In high-quality scissors the blades can be both extremely sharp, and tension sprung - to increase the cutting and shearing tension only at the exact point where the blades meet. The hand movement (pushing with the thumb, pulling with the fingers in right handed use) can add to this tension. An ideal example is in high-quality tailor's scissors or shears, which need to be able to perfectly cut (and not simply tear apart) delicate cloths such as chiffon and silk.

Children's scissors are usually not particularly sharp, and the tips of the blades are often blunted or 'rounded' for safety.

Mechanically, scissors are a first-class double-lever with the pivot acting as the fulcrum. For cutting thick or heavy material, the mechanical advantage of a lever can be exploited by placing the material to be cut as close to the fulcrum as possible. For example, if the applied force (at the handles) is twice as far away from the fulcrum as the cutting location (i.e., the point of contact between the blades), the force at the cutting location is twice that of the applied force at the handles. Scissors cut material by applying a local shear stress at the cutting location which exceeds the material's shear strength.

Some scissors have an appendage, called a finger brace or finger tang, below the index finger hole for the middle finger to rest on to provide for better control and more power in precision cutting. A finger tang can be found on many quality scissors (including inexpensive ones) and especially on scissors for cutting hair (see hair scissors pictured below). In hair cutting, some claim the ring finger is inserted where some place their index finger, and the little finger rests on the finger tang.

For people who do not have the use of their hands, there are specially designed foot operated scissors. Some quadriplegics can use a motorized mouth-operated style of scissor.

Culture: Due to their ubiquity across cultures and classes, scissors have numerous representations across world culture.

Art: Numerous forms of art worldwide enlist scissors as a tool/material with which to accomplish the art; in this section, we will be looking at cases where scissors appear in or are represented by the final art product.

Film: Edward Scissorhands is a 1990 film starring Johnny Depp as a young man who has hands made of multiple pairs of scissors. Running with Scissors is a 2006 film based on the memoir of the same title.

Games: The game Rock-Paper-Scissors involves two or more players making shapes with their hands to determine the outcome of the game. One of the three shapes, 'scissors', is made by extending the index and middle fingers to mimic the shape of most scissors.

In the horror game series, Clock Tower, There is a character called Scissorman, who has a variety of identities as the main antagonist throughout the series. Scissorman is a demonic serial killer with a giant pair of scissors and will kill anyone without even showing a sign of mercy or remorse.

Literature: Augusten Burroughs' 2002 memoir Running with Scissors spent eight weeks on the New York Times best seller list. The book was later adapted into a film.

Music: Running with Scissors is the title of a 1999 album by "Weird Al" Yankovic. The song "The Tailor Shop on Enbizaka (円尾坂の仕立屋 Enbizaka no Shitateya)" from Vocaloid producer Akuno-P tells a story about a tailor that kills a man and his family, whom she mistakes for her unfaithful lover and his three mistresses, using her sewing scissors. The XTC song "Scissor Man", later covered by Primus. "Save Your Scissors" - song by City and Colour. Sport: The term 'scissor kick' may be found in several sports, including:

Scissor kick (strike), a generic martial arts term for any of a number of moves that may resemble the appearance or action of a pair of scissors. Bicycle kicks in football are sometimes known as 'scissor kicks'. Swimming strokes including the sidestroke incorporate a leg movement often known as a 'scissor kick'.

Superstition: Scissors have a widespread place in cultural superstitions. In many cases, the specifics of the superstition may be specific to a given country, region, tribe, religion or even situation.

Africa: In parts of North Africa, it was held that scissors could be used to curse a bridegroom. When the bridegroom was on horseback, the person enacting the curse would stand behind him with the scissors open and call his name. If the bridegroom answered to his name being called, the scissors would then be snapped shut and the bridegroom would be unable to consummate his marriage with his bride.

Asia: In Pakistan, some believe that scissors should never be idly opened and closed without purpose. This is believed to cause bad luck.

North America: United States In New Orleans, some believed that putting an open pair of scissors underneath your pillow at night was a sound method for sleeping well, even if one might be cursed.

Eastern Europe: It is believed in some Eastern European countries that leaving scissors open causes fights and disagreement within a household.

China: It is believed in China that giving scissors to a friend or loved ones is to be cutting ties with them.

Science: Scissors have been used in the sciences for various purposes, including descriptions of animals or natural features.

Stapler

A stapler is a mechanical device that joins pages of paper or similar material by driving a thin metal staple through the sheets and folding the ends. Staplers are widely used in government, business, offices, homes and schools.

The word "stapler" can actually refer to a number of different devices of varying uses. In addition to joining paper sheets together, staplers can also be used in a surgical setting to join tissue together with surgical staples to close a surgical wound (much in the same way as sutures).

Typically, most staplers are used to join multiple sheets of paper. Paper staplers come in two distinct types: manual and electric. Manual staplers are normally hand-held, although models that are used while set on a desk or other surface are not uncommon. Electric staplers exist in a variety of different designs and models. Their primary operating function is to join large numbers of paper sheets together in rapid succession. Some electric staplers can join up to 20 sheets at a time.

A staple gun is usually a heavier duty, hand-held device; it can be strictly manual or pneumatic. Typical staplers are a third-class lever.

History:

The first known stapler was made in the 18th century in France for King Louis XV. Each staple was inscribed with the insignia of the royal court, as required. The growing uses of paper in the 19th century created a demand for an efficient paper fastener.

A McGill stapler In 1866, George McGill received U.S. patent 56,587 for a small, bendable brass paper fastener that was a precursor to the modern staple. In 1867, he received U.S. patent 67,665 for a press to insert the fastener into paper. He showed his invention at the 1876 Centennial Exhibition in Philadelphia, Pennsylvania, and continued to work on these and other various paper fasteners throughout the 1880s. In 1868 a patent was also taken out for a stapler in England by C.H.Gould. As well, also in 1868, Albert Kletzker of St Louis, MO patented a device to staple paper.

In 1877 Henry R. Heyl filed patent number 195,603 for the first machines to both insert and clinch a staple in one step, and for this reason some consider him the inventor of the modern stapler. In 1876 and 1877 Heyl also filed patents for the Novelty Paper Box Manufacturing Co of Philadelphia,PA, However, the N. P. B. Manufacturing Co.'s inventions were to be used to staple boxes and books.

The first machine to hold a magazine of many preformed staples came out in 1878.

On February 18, 1879, George McGill received patent 212,316for the McGill Single-Stroke Staple Press, the first commercially successful stapler. This device weighed over two and a half pounds and loaded a single 1/2 inch wide wire staple, which it could drive through several sheets of paper.

The first published use of the word "stapler" to indicate a machine for fastening papers with a thin metal wire was in an advertisement in the American Munsey's Magazine in 1901.

In the early 1900s, several devices were developed and patented that punched and folded papers to attach them to each other without a metallic clip. The Clipless Stand Machine (made in North Berwick) sold from 1909 into the 1920s. It cut a tongue in the paper that it folded back and tucked in. Bump's New Model Paper Fastener used a similar cutting and weaving technology.

In 1941 the type of paper stapler that is the most common in use today was developed: the four way paper stapler. With the four way, the operator could either use the stapler to staple papers to wood or card board, or used to staple like pliers for bags, or the normal way with two options, one the standard with the staples going inward or turning the plate and the staples going outward.

Methods:

An exploded view drawing Permanent fastening binds items by driving the staple through the material and into an anvil, a small metal plate that bends the ends, usually inward. On most modern staplers, the anvil rotates or slides to change between bending the staple ends inward for permanent stapling or outward for pinning. Clinches can be standard, squiggled, flat, or rounded completely adjacent to the paper to facilitate neater document stacking.

Pinning temporarily binds documents or other items, often cloth or clothing for sewing. To pin, the anvil slides or rotates so that the staple bends outwards instead of inwards. Some staplers pin by bending one leg of the staple inwards and the other outwards. The staple binds the item with relative security, but is easily removed.

Tacking fastens objects to surfaces, such as bulletin boards or walls. A stapler that can tack has a base that folds back out of the way so staples drive directly into an object rather than fold against the anvil.

Saddle staplers have an inverted "V"-shaped saddle for stapling pre-fold sheets to make booklets.

Stapleless staplers, invented in 1910, are a means of stapling that punches out a small flap of paper and weaves it through a notch. A more recent alternative method avoids the resulting hole by crimping the pages together with serrated metal teeth instead.

Gears

Gears may be defined as any toothed member designed to transmit motion or power from one shaft to another preferably if the distance between the two shafts is small. It is a positive and smooth drive.

Gears are generally used for one of four different reasons:

1. To reverse the direction of rotation.
2. To increase or decrease the speed of rotation.
3. To move rotational motion to a different axis.
4. To keep the rotation of two axes synchronized.