American Journal of Biomedical Science and Engineering 2017; 3(1): 8-14 http://www.aascit.org/journal/ajbse ISSN: 2381-103X (Print); ISSN: 2381-1048 (Online) An Automated Scotch Yoke Mechanism Oladejo Kolawole Adesola1, *, Samuel Ajibola Oluwagbemileke1, Oriolowo Kolawole Taofik2, Adetan Dare Aderibigbe1, Adekunle Nurudeen Olakunle3 1Department of Mechanical Engineering, Obafemi Awolowo University, Ile Ife, Nigeria 2Department of Industrial and Production Engineering, University of Ibadan, Ibadan, Nigeria 3Department of Mechanical Engineering, Federal University of Agriculture, Abeokuta, Nigeria Email address [email protected] (Oladejo K. A.), [email protected] (Oladejo K. A.), [email protected] (Oladejo K. A.), [email protected] (Oriolowo K. T.) Keywords Citation Angular Speed, Oladejo Kolawole Adesola, Samuel Ajibola Oluwagbemileke, Oriolowo Kolawole Taofik, Adetan Velocity, Dare Aderibigbe, Adekunle Nurudeen Olakunle. An Automated Scotch Yoke Mechanism. Linear Velocity, American Journal of Biomedical Science and Engineering. Vol. 3, No. 1, 2017, pp. 8-15. Scotch Yoke Mechanism, Model Abstract This paper addressed the relationship between linear velocity of a scotch yoke mechanism during motion. Understudying the working principle of the scotch yoke mechanism as regards to how it converts circular motion into linear motion. Received: March 16, 2017 Experimental apparatus were set up which involves calibrating of the motor speed, Accepted: April 18, 2017 calibrating of the motor speed, calibrating the timing of the circuit from theoretical Published: June 3, 2017 knowledge which led to the scotch yoke mechanism model construction. Mono–stable multi–vibrator and DC motor speed controller circuits were introduced into the design. Linear velocity produced independently by Tachometer and Timer circuit experiment was determined. There is close relationship between the angular speed and linear velocity produced from the Tachometer experiment and the timer circuit experiment, which helps to have a model for demonstrating the motion conversion characteristics of the scotch yoke mechanism. These findings demonstrated the motion characteristics of the scotch yoke mechanism; also the model will be useful in teaching and research purposes. 1. Introduction The Scotch Yoke Mechanism is a fairly simple mechanism for converting the linear motion of a slider into rotational motion or vice-versa. The parts of this device include a sliding bar, a yoke on the bar with a slot cut out, and a smaller bar connected to the yoke and affixed by a pin through the yoke slot to the sliding bar. As the bar slides back and forth, or reciprocates, the smaller bar is forced to slide up and down in the yoke slot, creating a rotational movement. The converse of this motion relationship is also true; as the pin initiates a rotational movement, the slider correspondingly generates a reciprocal or back and forth movement. In operation, the reciprocating part is directly coupled to the sliding bar or yoke with a slot that engages the pin on the rotating part. The motion of the Scotch Yoke Mechanism is such that pure simple harmonic motion is produced by the mechanism when driven by an eccentric or crank. Because velocity and acceleration are derivatives of the displacement time curve these graphs also have a perfect wave form. Scotch Yoke Mechanism is most commonly used in control valve actuators in high- pressure oil and gas pipelines. Although not a common metalworking machine nowadays, crude shapers also use Scotch yokes. It has been used in various internal American Journal of Biomedical Science and Engineering 2017; 3(1): 8-14 9 combustion engines, such as the Bourke engine, SyTech experiments remains a challenge, a synthetic, controlled study engine, and the Waissi engine. Some other contemporary uses of insect-like flapping is not only of engineering value, but include Can Crusher Machines, Power Operated Hairbrushes, also of biological relevance. For this application, insect-like and Medical/Dental aid robots. Junzhi, et al., (2009), flapping wings are an attractive solution and hence the need to addressed the design, construction, and motion control of an realize the functionality of insect flight by engineering means. adjustable Scotch yoke mechanism generating desired Since the semi-span of the insect wing is constant, the kinematics for dolphin-like robots. Since dolphins propel kinematics are spatial; in fact, an approximate figure-of- themselves by dorsoventral oscillations following a sinusoidal eight/banana was traced on a sphere. Hence a natural path with alterable amplitudes, a two-motor-driven Scotch mechanism implementing such kinematics should be (i) yoke mechanism is adopted as the primary propulsor to spherical and (ii) generated mathematically convenient curves produce sinusoidal oscillations, where a certain combination of expressing the figure-of-eight/banana shape. a leading screw mechanism and a rack and pinion mechanism Scotch Yoke is equivalent to the slider crank mechanism of driven by the slave motor are incorporated to independently conventional reciprocating compressors when the connecting change the length of the crank actuated by the master motor. rod is imagined to have an infinite length. Since pure harmonic Meanwhile, the output of the Scotch yoke, i.e., reciprocating motion is generated, shaking forces occur only at the motion, is converted into the up-and-down oscillations via a fundamental running frequency of the compressor and perfect rack and gear transmission. A DSP-based built-in motion dynamic balance is possible. This feature plus a compact control schemeis then brought forth and applied to achieve design are the major advantages of a Scotch-yoke mechanism dolphin-like propulsion. Their preliminary tests, in a robotics in compressor design. Until recently, Scotch-yoke mechanisms context, confirmed the feasibility of the devised mechanism have been utilized only in compressors of relatively small severing as a dedicated propulsor for bio-inspired movements. capacity. For the application discussed herein, a Scotch-yoke Manthan, et al., (2015), presents the automation of elliptical mechanism has been employed in a line of four cylinder trammel mechanism by applying rack and pinion and DC hermetic compressors ranging in capacity from 90,000 BTIJH Motor arrangement on the rod of the trammel which moves on to 145,000 BWH. With this design, two pair of opposed the channel. The power was supplied by batteries and the pistons are employed perpendicular and in slightly offset entire system was carried out to have its operation by making planes, Elson and Amin, (1974). Gregory, et al., (2003), ellipses of varying sizes. Moreover, a compass system attached developed a model which was initially non dimensional and at the end of the pinion made it easy to fix and remove the simplified under conditions of large numbers of cycles, to cutting tools of every kind. Equations relating the position of predict the importance of including coupling based solely on a two sliders with the position of drawing or cutting element ratio of maximum allowable wear depth to the crank radius. provided at the end of connecting rod were derived. The results Experiments show a linear progression of wear over two were experimentally verified by fabricating an elliptical distinct regions, suggesting a sudden transition in wear modes trammel and drawing ellipses from it. The sliders of the just after 1.5 million cycles. The need for cycle or time mechanism move perpendicular to each other and the drawing dependent wear rates in analysis, which is a potentially far or cutting element produces the ellipse on the required surface more significant source of error, is clearly illustrated by the and of the required major and minor axes which in turn experiment and discussed. Objectives of this experimental provides a very convenient mechanism for cutting out elliptical paper is to determine what relationship exists between linear pieces of whatever sizes out of any kind of material. Angular Speed and Linear Velocity of a Scotch yoke Galinski and Zbikowski, (2005), described the rationale, Mechanism as it engages in motion by: (i) Understudy the concept, design and implementation of a fixed-motion working principle of the Scotch yoke mechanism and study (nonadjustable) mechanism for insect-like flapping wing micro how it converts circular motion into linear motion, and (ii) To air vehicles in hover, inspired by two-winged flies. This spatial construct a model as a means of experimental evaluation of the (as opposed to planar) mechanism was based on the novel idea output motion of the Scotch Yoke mechanism. of a double spherical Scotch yoke. The mechanism was constructed for two main purposes: (i) as a test bed for aeromechanical research on hover in flapping flight, and (ii) as aprecursor design for a future flapping wing micro air vehicle. Insects fly by oscillating (plunging) and rotating (pitching) their wings through large angles, while sweeping them forwards and backwards. During this motion the wing tip approximately traces a ‘figure-of eight’ or a ‘banana’ and the wing changes the angle of attack (pitching) significantly. The kinematic and aerodynamic data from free-flying insects were sparsed and uncertain, and was not clear what aerodynamic consequences different wing motions have. Since acquiring the 1 – Crank, 2 – link, 3 – Pivot, 4 – Slider. necessary kinematic and dynamic data from biological Figure 1. Scotch Yoke Mechanism. 10