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Pump drill: A superb device for converting translational motion into high-speed rotation

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Abstract

Pump drill is an easily constructed ancient device that has been used for centuries to start fires and bore holes. It can effectively transfer rhythmic translational motions into vibratory, bi-directional rotary insertions. Here we explore, both experimentally and theoretically, the kinematics, dynamics, and potential applications of pump drills. The theoretical model, validated by experimental measurements, enables us to obtain the optimal structural geometries (e.g., the thread length and the crossbar span) of pump drills that maximize the mechanical responses such as the winding angle of the threads. Furthermore, the dependence of its rotational speed and piercing force on the loading conditions is investigated. Finally, manually powered devices, including an electric generator and a centrifugal separator, are developed based on the pump drill. This study paves a way towards promising applications of the pump drill in, for instance, energy harvesting and centrifugation.

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... [16] and [17] and the many references cited therein). Recent contributions to the literature on the mechanics of helical rods include [18][19][20][21][22]. With respect to this recent literature, the main differences of our research consist in the type of structure analyzed, and in the generality of the allowed deformations, i.e., rods are not assumed to remain circular helices a priori and can deform into helical shapes with nonconstant curvature and torsion. ...
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... The theoretical model presented in this work can help design and optimize a general class of helical structures, which has a promise in analyzing and predicting the unique mechanical behavior of high-performance thread materials and devices, for example, the artificial muscles and actuators, 2,41 the buzzer prototype, 42 and the pump drill. 43 Finally, it is noteworthy that the deformation of real hierarchical helical structures is usually complicated, and there are many factors that may influence their mechanical responses. Some limitations of the model have to be mentioned. ...
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Many motile species of bacteria are propelled by flagella, which are rigid helical filaments turned by rotary motors in the cell membrane. The motors are powered by the transmembrane gradient of protons or sodium ions. Although bacterial flagella contain many proteins, only three-MotA, MotB and FliG-participate closely in torque generation. MotA and MotB are ion-conducting membrane proteins that form the stator of the motor. FliG is a component of the rotor, present in about 25 copies per flagellum. It is composed of an amino-terminal domain that functions in flagellar assembly and a carboxy-terminal domain (FliG-C) that functions specifically in motor rotation. Here we report the crystal structure of FliG-C from the hyperthermophilic eubacterium Thermotoga maritima. Charged residues that are important for function, and which interact with the stator protein MotA, cluster along a prominent ridge on FliG-C. On the basis of the disposition of these residues, we present a hypothesis for the orientation of FliG-C domains in the flagellar motor, and propose a structural model for the part of the rotor that interacts with the stator.
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Mechanical Movements, Powers and Devices
  • G D Hiscox
G.D. Hiscox, Mechanical Movements, Powers and Devices, Norman W. Henley Publishing Company, 1903.
Primitive Technology: A Book of Earth Skills
  • D Wescott
D. Wescott, Primitive Technology: A Book of Earth Skills, Gibbs Smith, 1999.
Fabricated: The New World of 3D Printing Recent progress in soft lithography
  • H Lipson
  • M Kurman
H. Lipson, M. Kurman, Fabricated: The New World of 3D Printing, John Wiley & Sons, 2013. [16] J.A. Rogers, R.G. Nuzzo, Recent progress in soft lithography, Mater. Today 8 (2005) 50–56.
Multifunctional carbon nanotube yarns by downsizing an ancient technology
  • M Zhang
  • K R Atkinson
  • R H Baughman
M. Zhang, K.R. Atkinson, R.H. Baughman, Multifunctional carbon nanotube yarns by downsizing an ancient technology, Science 306 (2004) 1358-1361.
Fabricated: The New World of 3D Printing
  • H Lipson
  • M Kurman
H. Lipson, M. Kurman, Fabricated: The New World of 3D Printing, John Wiley & Sons, 2013.