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Research Papers

Improvement in Ballistae Design From Eutitonon to Palintonon: A Study on the Mechanical Advantages

[+] Author and Article Information
C. Rossi

e-mail: cesare.rossi@unina.it

S. Pagano

D.I.M.E.,
Department of Mechanical Engineering for Energetics,
University of Naples “Federico II,”
Via Claudio, 21 80125 Naples, Italy

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received October 11, 2012; final manuscript received April 23, 2013; published online June 10, 2013. Assoc. Editor: Hong-Sen Yan.

J. Mech. Des 135(8), 081006 (Jun 10, 2013) (7 pages) Paper No: MD-12-1511; doi: 10.1115/1.4024371 History: Received October 11, 2012; Revised April 23, 2013

This study investigated why the design of ancient throwing machines evolved from eutitonon (arms outside the mainframe) to palintonon (arms inside the mainframe) from the end of the first century B.C. to the first century A.D. and evaluated the mechanical advantages of the new design. Palintonon was first used for big machines; in the following centuries, it was also used for much smaller machines. Essentially, the palintonon design has several advantages: more elastic energy can be stored in the hair bundles representing the motors of these machines, heavier projectiles can be thrown with the same charging effort, projectiles are stressed by lower acceleration in the machine with the same muzzle velocity, and the throwing machines have higher efficiency. Results are also presented regarding the “internal ballistics” of these ancient throwing machines by using simulation software.

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Figures

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Fig. 2

Reconstruction of a Roman ballista (archaeological area of Saepinum, Campobasso-Italy, courtesy of Dr. F. Russo) and an author's virtual reconstruction of the torsion motor

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Fig. 3

(a) Maximum twist of the bundle versus L/D ratio and (b) elastic energy versus rotation [4]

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Fig. 4

Schemes of the eutitonon and palintonon designs

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Fig. 5

Projectile velocity versus arm position

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Fig. 6

Force of inertia on the projectile versus arm rotation

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Fig. 7

Projectile velocity versus arm position

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Fig. 8

Force of inertia on the projectile versus arm rotation

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Fig. 9

Projectile velocity versus arm position

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Fig. 10

Force of inertia on the projectile versus arm rotation

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Fig. 11

Eutitonon model and projectile velocity as a function of time during the launch run

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Fig. 12

Palintonon model and projectile velocity as a function of time during the launch run

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