THE ATLATL RESEARCH OF BOB PERKINS
Pronounce it "ott-lottle"
Bob Perkins of BPS Engineering has been interested in atlatl and dart mechanics for decades. BPS engineering claims credit for four major and half a dozen minor discoveries in the field. Onagocag Publishing is pleased to be able to present Mr. Perkins papers on Atlatl mechanics as part of The History and Primitive Technology Page.
ATLATL WEIGHTS: FUNCTION AND CLASSIFICATION
Atlatl weights, both known and suspected, are a fascinating and frustrating subject. Based soley on the misinterpretation and lack of understanding surrounding them, and their occurrance in the archealogical record, debate and confusion as to their purpose has set them apart from most other artifacts.
There are a variety of atlatl weight types and suspected types found, interestingly enough, mainly in the United States. Their distribution seems to be contained within the forty-eight states with a little overlap north into Canada and south of the Rio Grande iinto Mexico. But generally, the political boundries of the lower 48 states hold most of the world's alatl weights. As far as I am aware, atlatl weights do not occur outside of North America, although atlatls most certainly do. Atlatls in a variety of styles are found more or less world wide. The earliest examples date to well over 20,000 BP in Europe, and the atlatl is still used today by the natives of Papua, New Guinea and the Australian aborigines. But regardless of where atlatls are found, nowhere other than North America are they found with weights attached to them.
The confusion surrounding atlatl weights begins with the many theories as to their purpose. The most popular of these seems to be that they are a counter balance. This theory suggests that the weight acts as an adjustment to balance the atlatl and dart in the palm of the hand. Many theories have been put forth, mainly based on the idea that the adjustment of the weight would propel the dart a greater distance.
Experimentation with many of these theories tended to show the opposite result until finally the theory of last result, "hunting magic" was applied. When all else fails, it's a charm, the owner believed the atlatl weight possessed "hunting magic." No doubt about it, some weights are quite beautiful and finely polished, and I am sure their owners even believed they possessed magical power. That's just the way we humans are. We're weird like that. However, not all atlatl weights are beautiful. Many are rather crudely finished and some are rounded river rock. Even these could hold some special meaning to someone, but the "charm" theory just doesn"t hold. Atlatl weights have a function, and that function has to so with their mass.
This brings us to the contradiction in the term "atlatl weight". More often than not atlatl weights are referred to in every descriptive term imaginable except-mass. To apply the term 'weight' to an object and neglect to report its mass would seem illogical to a thinking human.
There is also the confusion of what is an atlatl weight. This is more of a word game than a question of function. Depending upon where you live or how you became familiar with atlatl weights you might refer to all weights in general as banner stones, boat stones, counterweights, bird stones, etc.
The center of all this confusion lies with the dispute over the true purpose of the atlatl weight. In my studies I have found that they possess a deceptively advanced technology. The basic technology, the mechanical foundation of the system, is the flexible dart. Over time humans have tinkered and toyed with this system, improving and refining it to a very high degree.
Atlatl weights possess mass and when attached to an atlatl the mass effects the system. But contrary to popular opinion you can't just strap a weight on to any old atlatl and expect a miracle.
Atlatl weights do not possess sufficient mass to significantly influence the speed at which an atlatl is swung in order to affect some degree of timing based on velocity. The fact that a weight increases the moment of inertia of an atlatl is just that, a fact. But what good does it do? Why not make a thicker atlatl? And as far as a counterbalance is concerned, that theory only applies when the atlatl and dart are at rest and not being used. The presence or absence of a weight makes no difference whatsoever as to how long or steady an atlatl and dart can be held.
The purpose of the weights mass is to resist acceleration. In order to understand its function of resisting acceleration a review of the technological evolution of the atlatl and dart must come first.
The basic mechanics of the system depend exclusively on the flexibility of the dart. When the dart is accelerated by the atlatl it flexes and stores energy like a spring. At some point during the swing, after the atlatl is no longer accelerating sufficiently to cause further compression of the dart, the dart then uses its stored energy to push itself away from the atlatl. This allows the dart a smooth separation between itself and the atlatl, giving it an effective and powerful launch.
One of the great evolutionary improvements to the system was superimposing flexibility into the atlatl. If this is incorporated successfully into the system, with the degree of flexibility of both atlatl and dart in a functioning relationship with one another, their function will be similar to that of a diver diving from a spring board. In this system the diver's legs are bent, like the dart, and store energy to be used to push away from the diving board. The diving board, like a flexible atlatl, is also bent back, storing energy to be used to push the diver away from the board. With the diver and diving board pushing each other away at the same time, the launch of the diver is considerably higher, smoother, and more powerful than if the diver had used a fixed rigid platform.
When the proper mathematical relationships of length and flexibility between atlatl and dart are achieved, the results are a long and noticeably flexible dart. But the atlatl on the other hand is, at approximately one third the length of the dart, short and somewhat stiff. The proper flexibility of an atlatl is rather subtle. The atlatl which is correctly flexed seems too stiff to be of any benefit. This is where the atlatl weight is applied to the system.
What atlatl weights accomplish in this system with the flexible atlatl is rather sophistocated and ingenious, representing a level of engineering skill which is impressive even by today's standards. Its mass, located approximately in the middle of the atlatl shaft, resists acceleration, (Newton's First Law of Motion) and forces the atlatl to deflect than is possible without it. This enables the atlatl to store more spring energy to be used to push the dart away from the atlatl. The weight's position along the atlatl shaft influences the amount and rate at which energy is stored and released. Therefore, the atlatl weight is a timing device influencing the amount and rate at which the spring energy of an atlatl is stored and released against the spring energy of a dart. That is its primary function. Its effects on the system are not so profound as to propel the dart to a noticeably greater distance or velocity, although higher velocities are achieved. When properly incorporated into the system, the weight improves the performance of that system in terms of efficiency. Smoother, more controlled, and powerful launches make for better accuracy. And ultimately, it is getting to the target that counts.
Now that the atlatl weight function has been firmly established, the problem of classification can be more easily addressed. Archaeologists have attempted to classify weights according to their shape and hafting technique. In this they have failed miserably. Not only have the same weights been placed in a category Type III by one archaeologist and a Class I category by another, but some categories contain only one known example. This being the case I have laid down the framework for a new system of weight classification based solely on function and effect.
The basic atlatl weight, or Type I in the Perkins' atlatl weight classification, is a single point mass weight with a mass of approximately 65 g. No matter how it is grooved, holed, shaped, or hafted to the atlatl its final position is that point at which its mass influences the mechanics of the system. Type II weight causes a finer, more precise response to the flex of the atlatl, accomplishing with one weight what was attempted with several. This brings us to the most fascinating weight to be classified.
Type III Stealth Weight
The Type III stealth weight is more commonly known as a Banner Stone, and there is some dispute as to whether they are atlatl weights or not. Based mainly on evidence from Indian Knoll, Kentucky where Banner Stones have been recovered in context and in alignment with atlatl hooks and antler handles, I believe that Banner Stones are indeed atlatl weights.
Mechanically the mass of Banner Stones tend to influence the system like a Type I weight, but their shape has the interesting effect of silencing the noise caused by the swing of the atlatl. Usually when a stick or atlatl is swung, an audible "zip-like" noise is generated. It seems that when a Banner Stone is attached this noise is significantly reduced generating more of a low frequency "woof".
Since first discovering this effect I've demonstrated it to several people. At distances of anywhere from 5 to 15 meters I have asked observers to listen for a difference in sound levels between an atlatl equipped with a Type III stealth weight and an atlatl with only a Type I point mass. After three swings with each all observers reported a significant difference in that the stealth atlatl was noticeably quieter than the other. On the offhand chance that my observers were predisposed to report a difference in sound by being asked to "listen", I began asking subsequent observers to "watch" for a difference between the test atlatls.
The fact that these observers were asked to watch for an effect as opposed to listen resulted in a tendency to be more hesistant when reporting what was noticed after having the atlatls swung in front of them. But again in all cases, they reported that the atlatl with the Banner Stone was considerably quieter than the other atlatl. This result suggested that the effect was so profound that observers, led to believe they were looking for an effect with their eyes, none the less noticed an effect with their ears.
I arranged for an electronic sound test to be conducted at the 1992 Rabbit Stick Rendezvous. Sound equipment from Ricks College was made available to me for this purpose. The equipment provided was so sophistocated that its technology had only been available within the past three years. The microphones, about three feet long and four inches in diameter could, on a calm day, more than likely detect the sound of a needle being dropped into a haystack.
I used the same two atlatls as for the observational studies. Each atlatl was swung three times with and without the use of darts. A total of ten separate comparisons were made and recorded on magnetic tape. The five comparisons were made shooting the darts over the head of the technician handling the microphone and all traveled approximately the same distance. This was done in case someone suggested that I was swinging the stealth atlatl differently from the other atlatl. The deviation in throwing was held to an absolute minimum. In fact, I maintained a degree of consistency surprising even to myself, since I was concentrating on NOT hitting the sound man more than anything else during this portion of the experiment. None the less, it should be noted that all darts traveled over the head and landed behind this trusting soul at a surprisingly consistent height and distance respectively.
The data recorded on tape was analyzed by computer and for all ten comparisons the stealth atlatl registered significantly lower sound levels than the unsilenced atlatl.
Although a mathematical module of this effect has not been formulated, the focus of maximum sound suppression seems to be between 20 and 25 meters indicating an effect known as superposition of sound waves. But no matter what the mathematics are, the effect is definitly present.
Although these experiments may not confirm that the effect of sound suppression was the purposeful function related to the shape of banner stones, they certainly go a long way to indicate it. And as far as the actual advantage of noiseless atlatls is concerned, I will leave that to other researchers to contemplate, since they no longer have the "counter balance" theory to consider.
Click the links below for more of Bob Perkins' atlatl papers.
This page was last updated on 07 March 2012.
Copyright © 1998 & 2012 by Wyatt R. Knapp