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Statics
Published in J.N. Fawcett, J.S. Burdess, Basic Mechanics with Engineering Applications, 2012
A capstan is a device used to produce large tensions in ropes. The most common application is in mooring ships to docks. The capstan consists of a rotating drum, usually with a vertical axis, which is driven at a slow speed. A rope is looped around the drum as shown in Fig. 3.77. When T2 = 0, or is very small, slip occurs between the rope and drum. If a small tension is now applied by hand, so increasing T2, the resulting value of T1 will depend upon the coefficient of friction between the rope and the drum and the angle of wrap of the rope on the drum. Let us consider the effect of the number of turns of rope on the drum. From eqn (vii)T2=T1e−μ2πn,
Reliability maintenance aspects of deck machinery for ageing/aged fishing vessels
Published in Journal of Marine Engineering & Technology, 2022
David Kimera, Fillemon Nduvu Nangolo
The maintenance of deck machinery systems beyond their useful lifetime is paramount in order to ensure the safety of the operators and keep downtime at its optimal base. A re-maintenance plan/strategy is recommended where the vessel owners/managers should emphasise scheduled maintenance checks and reports from the maintenance crew on a weekly basis. For reliability prediction of ageing deck machinery, degradation data such as crane drop load, crane load capacity, winch loads, winch load tension, capstan rpm, crane/capstan brake power among others, ought to be used in preference to only failure data because degradation can be modelled using several approaches. These degradation data trends can be used by the maintenance crew to further analyse machinery performance and maintenance options. When using reliability software, field data and machine specifications ought to be incorporated for best interpretation of the software output results. There is a need to carry out fatigue tests on aged/ageing deck machinery in order to ascertain the fatigue-failure relationship and how fatigue affects the reliability of such machinery.
Design of a 6-DOF force device for virtual assembly (FDVA-6) of mechanical parts
Published in Mechanics Based Design of Structures and Machines, 2018
Q. H. Wang, S. C. Wu, J. W. Liu, J. R. Li
It is connected onto the base through capstan 3, which allows motor 3 (for joint 3) to be mounted on the base instead of mounting it directly onto the joint. In this way, the moving mass is greatly reduced. The rotation of joint 2 (around axis 2) is controlled by motor 2 (on capstan 1, hidden in Fig. 1). The design of each link considers the stability of the system, for, e.g., as designed, link 2 and link 3 are made unique to be assembled onto link 3 from the same side, so as to remarkably increase stiffness of the device as well as its dynamic stability. Link 2 can rotate around axis 2. Moreover, to allow a force control without extra cost associated with force sensors (Yoon et al. 2004), highly backdrivable and zero backlash cable capstan reducers are used on these three DOFs. And for stiffness and self-weight concerns, parts of the first component are made of aluminum alloy.
Theoretical modeling and characterization of bending properties of fabrics with friction and extensibility effect
Published in The Journal of The Textile Institute, 2025
Yi Sun, Yuan Tian, Dongming Zheng, Gui Liu, Xingxing Pan, Ning Pan, Zhaoqun Du
The force and moment equilibrium of an infinitesimal element and how it extends from to dl are shown in Figure 7. From the force balances along tangential and normal directions, and moment equilibrium at point O, the following three classical capstan equations are derived as follows where T, Q, M are the tension, shear force and bending moment, respectively; φ is an angle measured in the contact region; r1 is the half-height of the cross section, that is the half-thickness of samples.