The Effects of Initial Conditions on the Motion of the Boleadora WeaponJacob Brooks and Aaron Titus, Department of Chemistry and Physics, High Point University, High Point, NC

AbstractThe effect of the throwing technique on the mo-tion of a thrown boleadora from the point ofthe boleadora’s release to its full equidistantspread was investigated. The boleadora is an an-cient hunting weapon made of three individualmasses connected by rope to a common centerpoint. When the weapon is thrown, the threemasses initially travel together. Shortly after re-lease, the masses spread out around their com-mon center point, eventually ensnaring their tar-get. A computational model was developed andcompared to actual results measured with videoanalysis. In one case, the bola was thrown fromthe knot, and in the other case the bola wasthrown from one of the masses. Both the modeland results from video analysis are presented.

A gaucho throwing a boleadora.

Throwing Techniques

Boleadora thrown from knot.

Boleadora thrown from ball.

Video AnalysesTo fabricate the boleadora, we attached a set ofthree equally massive spheres with holes drilledthrough their centers to Berkley Trilene Big GameFishing Line with a breaking tension of fortypounds (about 178 N).

Traditional boleadora and fabricated boleadora.

We outfitted the boleadora with infrared reflectivemarkers on each mass and recorded data aboutthe boleadora’s flight using fourteen Raptor-12 in-frared cameras spaced as shown below. The datawas used to recreate visualizations of actual throwsin VPython.

Throwing and tracking the boleadora.

Raptor-12 infrared camera.

Results & Computational ModelThe boleadora, when thrown by holding the com-mon point, did not actually spin as one might ex-pect. Rather, the masses slowly spread as the sys-tem was in flight.

Boleadora thrown from knot.

The second technique of throwing from a mass re-vealed a clear rotational behavior in the system af-ter release.

Boleadora thrown from ball.

Future WorkIn the future, we will investigate the behavior ofthe boleadora with more than three spheres andwith different initial conditions. Furthermore,we will investigate the affect of mass and stringlength on the flight and dynamics of the bola.

In addition, the computational models will berefined. In the current models, the strings aretreated as very stiff springs and the spheres donot collide. While being swung, it is expectedthat the spheres will collide and eventually restagainst each other, yet the current computationalmodels allow the spheres to pass through eachother and oscillate back and forth before they arereleased. In future models, collisions betweenspheres will be added.

Finally, the photo of the gaucho shows someinitial spread in the bola, which was not evidentin the video analysis data. After computationalmodels are edited to included non-uniformcircular motion, various throwing motions willbe investigated to see if the bola spreads duringthe throw, before it is released.

References•VPython Software.

(www.vpython.org)

•Motion Analysis Software.(www.motionanalysis.com)

•D. L. Mathieson, “Wrap up rotational motionby throwing a bola,” Phys. Teach. 30, 180–181(March 1992).

•T. McCarthy, “Bola Motion,” Phys. Teach. 48,222-224 (April 2010).

Acknowledgments•Briana Fiser•Kevin Ford, Taylor Wimbish, and Danielle Paul

at High Point University for assistance with themotion capture system in the Human Biome-chanics and Physiology Lab.