Wedge (mechanical device)

Infobox tool
name = wedge

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caption =Woodsplitting wedge
other_name =
classification = Hand tool
types =
used_with =Sledgehammer
related = Chisel
Splitting maul
Axeotheruses2|Wedge

A wedge is a triangular shaped tool, a compound and portable inclined plane, and one of the six classical simple machines. It can be used to separate two objects, or portions of objects, lift an object, or hold an object in place. It operates by converting a force applied to the wide end into forces perpendicular to the inclined surfaces. The mechanical advantage of a wedge depends on the ratio of its length to its thickness. Where a short wedge with a wide angle does the job faster, it requires more force than a long wedge with a smaller angle.

History

The origin of the wedge is unknown, because it has been in use for over 9000 years. In Ancient Egypt quarrys, bronze wedges were used to break away blocks of rock used for construction. Wood wedges, that swelled after being wet, were also used. Some Native American tribes used antler wedges as a means of splitting and working wood to make canoes, houses, and other wood objects.

Examples for separating and lifting

Examples include axes, splitting mauls, and splitting wedges. Wedges can also be used to lift heavy objects, or finely adjust the height of objects, essentially separating them from the surface they rest on. These may also be referred to as shims. Knives, scissors, chisels, and even teeth can sometimes be used as wedges, however, they are more fundamentally cutting implements.

Examples for holding fast

Wedges can also be used to hold objects in place, such as engine parts (poppet valves), bicycle parts (stems and eccentric bottom brackets), and doors.

A door stop (door wedge) is a wedge, and its main function is to generate friction between the bottom of the door and the ground.

A fork or nails can also be considered a type of wedge. While a nail will slice into wood when hammered, a bolt will not be pushed in. This is because a nail is a wedge and a bolt is not. A nail is tapered to a point at its end, then gets thicker farther up towards the head of the nail.

Mechanical advantage

The mechanical advantage of a wedge is the length of the sloping side of the wedge divided by the width of the thick end of the wedge. Therefore the formula for a wedge is:

$MA=\{S\; over\; T\}$

In other words, divide the length of the wedge by its width at the thickest edge.

The more acute the angle of the wedge, the more mechanical advantage it will have.

Despite this, one reason that many splitting wedges have a wide angle is that an elastic material, such as wood, will bind a narrow wedge more readily than a wide wedge. This is why splitting mauls have a much larger angle than an axe.

ee also

* Axe
* Inclined Plane
* Screw
* Splitting maul

External links

* [http://em-ntserver.unl.edu/Negahban/em223/note16/note16.htm (Mechanics of) wedges and screws]