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Formal variation in Australian spear and spearthrower technology

TitleFormal variation in Australian spear and spearthrower technology
Publication TypeBook
Year of Publication1989
AuthorsCUNDY, B. J.
PublisherBAR International Series
Series Volume546
Number of Pages143
Publication LanguageEnglish
ISBN Number978-0860546931

J. Whittaker: [Actually covers only Central Australia and the northern half of the Northern Territory so some important types and variation not included. A very good study although marred by many typos and almost no illustrations of spearthrowers and spears. One of the best sources on spearthrower mechanics and physics, but the explanations are not always clear. I’ve translated into English as much as I can.]
1. Intro: Variation should be explained by technological and functional factors as well as cultural differences.
2. Technological comparison and performance: Compares to hand thrown spears. Tasmania had no spearthrower, hand thrown spears 40-70 yards, maybe up to 100m, typically spears 4m long, .6 kg. [He discounts shorter distance records as non-comparable, but these Tasmanian ones seem exaggerated, when javelin record is 98m.]
Spear thrower records: Falkenberg (1968) measured throws in Northern Territory of 90-125m, one 180m, but special gear – small reed spears. Thomson (unpub) recorded 49-105 m in Arnhem Land. Mountford (unpub) got 50-91 m. Consider 70 m as a “rule of thumb” average max distance, so not really better than hand thrown.
Accuracy is hard to compare from ethnographic accounts, but usual max accurate range 20 m. At moderate size targets, comparable accuracy to bow, but atlatl accuracy decreases more rapidly as target gets smaller or more distant. So why atlatl? Perhaps reduces necessity of learning throwing skills, i.e., it’s easier than hand throwing, both in skill and effort, freeing hunter to invest in other skills and activities. [I think he understates the improvement possible with spear thrower.]
3. Aerodynamic factors: “Vacuum model” of throw considers only gravitational and projection force, not aerodynamic factors, and predicts 45 degree angle for maximum distance throw. But drag (air friction) greatly reduces theoretical maximum. Spears unlikely to have much lift. Center of pressure must be behind center of gravity to keep straight flight, either by having most of the weight forward, or adding drag to rear of shaft, as in fletching. Most experiments suggest center of gravity should be between .25-.33 length on unfletched projectiles. Compares modern javelin, weighted and shaped to glide maximum distance but still land point first. “Range but not in-flight behavior equaled” by Australians. Palter (1977): 293 spears, center of gravity at .25-.48 length, thus many would stall if thrown for distance, but this was of secondary importance in their use.
4. Wound Ballistics: Penetration depends on motion and shape of projectile. Motion measured by kinetic energy, momentum, power, mass, and velocity, with most favoring kinetic energy. (Mass x velocity squared over 2). Because of drag from the material penetrated, heavier projectiles penetrate deeper than lighter higher velocity ones. Shape and size of missile affect drag. Surprisingly little energy is needed to penetrate skin and flesh.
5. Propulsion: Body levers in timed sequence, with slow but powerful (trunk, thighs) first, then faster but weaker joints (hands, arms), so each contributes its maximum. For light projectiles, skill (timing of muscle sequence) more important; for heavy, strength more important (e.g. baseball vs javelin). Mason (1884) and Howard (1974) use impulse model (atlatl increases time of thrust on spear). Howard’s model is unlikely on mechanical grounds, and predicts that spearthrower length is of little importance. Most analyses use lever model, seeing atlatl as lengthening arm. Atlatl is not a lever, but can be analyzed as part of lever system. [A confusing and unnecessary quibble. As subsequent discussion makes clear, atlatl and wrist do in fact act as lever and fulcrum.] Rotating short end of atlatl at wrist by applying strong force moves the long end a greater distance in the same time, thus faster, thus increasing velocity of spear. Analyzes 1970 ethnographic film of throwing. Motion is similar to conventional overhand throw, a sequence of 1) forward body motion, 2) shoulder rotation 3) arm rotation, and 4) wrist rotation [flexion]. Spearthrower increases length of resistance arm of any body lever in the same plane. If used more horizontally [side-arm], emphasizes shoulder + body rotation, if vertical, emphasizes arm and wrist. Stronger individuals may tend to use more vertically. Most of the gain in velocity is from wrist action in last .1 second of throw.
If spearthrower load is too great [too heavy, too much wind resistance] then velocity reduced. If too light, high acceleration reached at expense of power development.
Longer spear thrower increases linear velocity at tip (and spear) but increases load about the wrist faster because proportional to square of length between wrist and center of gravity of atlatl.
6) Spear and Spearthrower Articulation
At rest, atlatl weight bends wrist back, spear weight counters this, bends forward. Bannerstones may help balance, but not used in Australia.
As wrist flexes to lever spear thrower, and spear stays in line, the tail of the spear must rise, so spear must flex a distance proportional to the length of the atlatl. The flex also stores energy that can be converted into kinetic energy later, and add to spear velocity, but spear detaches from atlatl before that is complete, so some of the energy stored as flex remains, resulting in wave-like shaft vibration. If shaft does not store enough energy by flexing, it will be tipped toward the ground; too much and it may buckle.
Thrower must overcome inertia of spear and atlatl tip. Longer atlatl has higher velocity, but rapidly loses advantage because inertia is function of length squared, so doubling length quadruples inertia. Shorter atlatl, lower possible velocity, but can throw heavier spear. Different spear and atlatl combinations optimize for either high velocity with low energy (light spear), or high energy with low velocity (heavy spear). [Of course, but how then do Australians use combination of long (and heavy) atlatl with very long and heavy spear? Even with my lighter spears, their woomeras are too long for me. Tables show some spears 400-500 gms, 4 x what mine weigh.] Can make atlatl lighter as gets longer, but then need to increase rigidity because energy stored as atlatl flex will only be released at end of throw as lateral movement of spear shaft.
7) Structural relationships. 1. Positive correlation between mass of atlatl and mass of spear. 2. Inverse relation between length of atlatl and mass of spear. 3. Inverse between length and mass of atlatl. 4. If optimizing for high velocity, atlatl inertia may be reduced by concentrating mass about the wrist pivot, in which case mass and length may be positively correlated. Test on specimens from Northern Territory, 5 types of spearthrower, but can’t match individual spears to atlatls, uses sample means. Expectations generally confirmed.
8) Spear and Spearthrower forms.
Central Australian: Leaf, paddle, or scoop shaped, lashed on hook, resin lump at handle, often with inset stone flake. [What most people think of as Australian “woomera.”] Form linked to manufacture from cambium of mulga tree, and secondary uses as tray, club, musical instrument, etc. Appears inefficient – wind resistance of wide shape, but used either flat or edge-on.