Spear throwers are also called throwing board, Atlatl by the Aztecs (central Mexico), and Woomera by the Australian Aboriginies. A spear thrower is a stick that helps propel a spear with greater force. Spear throwers are one to three feet long with a handle at one end and a hook at the other that engages the butt end of the spear. The thrower is held behind the shoulder of the user, hook up, and the spear is placed along it so that the spear points forward and slightly upward. During the throw, the user keeps hold of the thrower which may have a thong tied to its end to go around their wrist or which may have finger loops. When throwing, the user swings their arm forward and snaps their wrist, launching the spear with great velocity from the end of the thrower, in this way taking advantage of the centrifugal force generated. The spear travels faster than if hand thrown because the extension of the throwing arm provides more leverage; the spear thrower’s end moves faster than the hand holding it.The spear thrower essentially increases the length of the arm of the person that is throwing the spear and therefore creates more power. The spear thrower can be considered a lever that propels the spear. The thrower acts as an extension of the arm, so that the spear is accompanied further in its trajectory and receives a much stronger parting thrust which results in a considerably longer trajectory.
There is a significant difference between the total
distance that the arm covers when throwing a spear and the total
distance that the spear thrower covers when throwing a spear .
The arm motion when throwing
a spear covers 130 degrees of a circle which is 36.1% of a whole
circle.
Considering that the circumference of a circle is calculated as (2
times
PI times r) where PI equals 3.14 and where r equals the radius of the
circle
(i.e. arm length or affective arm length with a spear thrower). The
distance
of the arc of motion that is covered by the arm of the thrower can be
calculated
as (2 times PI times r) times 36.1%. Without a spear thrower, the
arm
length is 33 inches, and the distance of the arc of motion is equal to
74.8
inches. With a spear thrower, the affective arm length is 52 inches,
and
the distance of the arc of motion is equal to 117.9 inches. The
difference
between these two measurements is 43.1 inches.
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This figure shows this principle when throwing a spear without a spear thrower and with an spear thrower. The spear is being throw from left to right. Line 1 is the starting place for either throw. Line 2 is the point of release for the spear for either throw. Arc 3 is the arc for the throw without a spear thrower. Arc 4 is the arc for the throw with a spear thrower. Point 5 is the pivot point at the shoulder of the thrower. The angle formed between Line 1 and Line 2 is 130 degrees. |
For more information about spear throwers, please see my SPEAR THROWER REFERENCE PAGE.
See some of the Spear Thowers that I have make in the
Spear
Thrower Photo Gallery of Carl Doney
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