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Atlatl Flexibility Analysis via Computer Modeling
by Dick Baugh
Extravagant claims have been made regarding the increased dart
velocity achieved with a flexible atlatl. This report quantifies
the increase inprojectile velocity or kinetic energy caused by
allowing the atlatl to flex. It is a summary of detailed
mathematical analysis on flexing atlatls. Themodel for the human
effort involved in throwing the dart with an atlatl was derived
from experimental data cited in "Atlatl Dynamics" by RichardBaugh,
published in Lithic Technology, Spring, 1998. The human effort
(force and torque versus hand position) involved in throwing is
assumed
be constant. It does not depend on the masses or dimensions of
the atlatl and projectile. The model for the flexing atlatl, shown
in Figure 1, consisof a rigid atlatl coupled to the dart via a
lossless spring. The dart mass and atlatl length and mass are
similar to those of BPS equipment. The dartvelocity was computed
for various values of spring stiffness. A perfectly rigid atlatl
would be represented by very large spring stiffness. It
isconvenient to characterize the atlatl stiffness by the distance
that the tip deflects during the act of throwing. Remember, the
human effort remains tsame so increased flexing is due to increased
compliance (flexibility) in the atlatl. The results are summarized
in Figures 2 and 3. These plots showthe kinetic energy and velocity
of the projectile as function of the amount that the spur deflects.
In order to achieve an 11 % increase in kinetic enethe tip of the
atlatl would have to deflect approximately 0.1 meters. These
results are for a specific thrower, atlatl and projectile. It is
difficult to
generalize the results however one can say that the increase in
projectile kinetic energy can be no more than the potential energy
stored in the flexinof the atlatl,
stored energy = (1/2)*applied torque*angular deflection of
atlatl.
The deflection angle in radians = (distance the atlatl tip
deflects)/(atlatl length).
A copy of Atlatl Dynamics can be obtained from the author for a
$2.00 handlingfee.
Dick Baugh, (650) 493-5125490 Gary Ct.Palo Alto, CA 94306
[email protected]
4/28/05 4:tlatl flexibility analysis via computer modeling
Pagettp://primitiveways.com/pt-atlatlflex.html
