UNIVERSITI TENAGA NASIONAL
COLLEGE OF ENGINEERING
MEMB331 MACHINE DESIGN & CAD LAB
SEMESTER 2 2016/2017
LAB 1: SLIDER CRANK CHAIN
EXPERIMENT
SECTION 4
GROUP 4
MOHD NAZIM BIN JAMALI
ME094660
SASIDEVAN A/L MUNUSAMY
ME096493
DENNIS BIN ABDUL ADAM
ME095476
LIONELL NITHIYA A/L NITHIYA SAGAYA
SEELAN
ME095508
15/11/2016
22/11/2016
22/11/2016
SUMMARY & OBJECTIVES
The Slider Crank Chain are an example of the two essential instruments which frame the fundamental for numerous more convoluted movements. In this experiment, the main aim is to come by a graph for velocity of
piston against angle of crank by utilizing the technique of instantaneous centers (the crank are assumed to rotate at an angular
velocity that is constant). Next, the focus is to acquire the angle of
crank that relates to the maximum velocity of piston and also to demonstrate that for a slider crank chain, the motion of piston approaches simple harmonic motion with ascending connecting rod values or ratio of the crank. The experiment is initiated with a
connecting rod of 115mm length. Cross scale readings and piston
displacement are recorded for every 10° increment of crank rotation. Then,
connecting rods of lengths 130mm and 175mm are tested with similar steps.
During the analysis, it was noted that graph obtained for piston displacement versus crank angle was a bell shaped graph. Then, it was observed that the maximum piston displacement occurs at a crank angle of 90° where the piston velocity is perpendicular to this value. Therefore, the maximum velocity also occurs at a crank angle of 90°. Meanwhile, the maximum acceleration occurs between the crank angle of 10° and 40° as
Result & Observation
Length of connecting rod: 115 mm Radius of crank: 35 mm
Crank Angle Piston Displacement, mm Piston Velocity, mm/s Piston Acceleration, mm/s² 0 60 44 0 10 61 50 0.6 20 62 58 0.8 30 65 64 0.6 40 69 69 0.5 50 75 74 0.5 60 80 76 0.2 70 87 78 0.2 80 92 78 0 90 99 77 -0.1 100 105 75 -0.2 110 111 71 -0.4 120 116 68 -0.3 130 120 64 -0.4 140 124 60 -0.4 150 128 56 -0.4 160 129 52 -0.4 170 130 48 -0.4 180 130 44 -0.4 190 130 41 -0.3 200 130 38 -0.3 210 127 33 -0.5 220 125 30 -0.3 230 122 27 -0.3 240 118 24 -0.3 250 114 20 -0.4 260 108 16 -0.4 270 101 13 -0.3 280 95 12 -0.1 290 90 12 0 300 81 13 0.1 310 78 14 0.1 320 72 19 0.5 330 68 22 0.3 340 64 30 0.8 350 61 36 0.6
Crank Angle Piston Displacement, mm Piston Velocity, mm/s Piston Acceleration, mm/s² 0 44 44 0 10 45 50 0.6 20 47 58 0.8 30 50 64 0.6 40 54 70 0.6 50 59 73 0.3 60 64 77 0.3 70 71 79 0.2 80 76 79 0 90 83 78 -0.1 100 90 75 -0.3 110 96 72 -0.3 120 101 69 -0.3 130 105 65 -0.4 140 109 61 -0.4 150 111 58 -0.3 160 113 53 -0.5 170 114 49 -0.4 180 115 45 -0.4 190 115 40 -0.5 200 114 37 -0.3 210 113 34 -0.3 220 110 29 -0.5 230 107 26 -0.3 240 103 23 -0.3 250 98 19 -0.4 260 92 15 -0.4 270 85 12 -0.3 280 80 12 0 290 74 12 0 300 67 13 0.1 310 62 15 0.2 320 57 18 0.3 330 52 23 0.5 340 49 30 0.7 350 47 35 0.3 360 46 45 1
Length of connecting rod: 175 mm Radius of crank: 35 mm
Crank Angle Piston Displacement, mm Piston Velocity, mm/s Piston Acceleration, mm/s² 0 0 45 0 10 1 50 0.5 20 2 58 0.3 30 4 64 0.8 40 8 69 0.5 50 13 73 0.4 60 18 76 0.3 70 24 78 0.2 80 31 78 0 90 37 78 0 100 43 76 -0.2 110 49 74 -0.2 120 54 71 -0.3 130 59 67 -0.4 140 63 63 -0.4 150 66 58 -0.5 160 68 54 -0.4 170 69 50 -0.4 180 70 45 -0.5 190 70 40 -0.5 200 70 36 -0.4 210 68 32 -0.4 220 66 28 -0.4 230 61 24 -0.4 240 57 21 -0.3 250 53 18 -0.3 260 46 14 -0.2 270 40 13 -0.1 280 35 12 -0.1 290 27 11 0.1 300 23 12 -0.1 310 17 15 0.3 320 12 18 0.3 330 8 23 0.5 340 4 29 0.6 350 2 35 0.6 360 0 44 0.9
Piston Acceleration = (Piston Velocity, i - Piston Velocity, i+1) / 10s = (50mm/s – 45mm/s) / 10s
= 0.5 mm/s²
Discussion
1. Based on the data collected, the graph obtained for displacement of the piston versus angle of crank was a graph with a bell shaped. Based on this graph that we have plotted, we can be observed that the displacement of piston is at the maximum value when the angle of crank is at 90˚. The reason is because the velocity of the piston is perpendicular to the displacement of the piston at the angle of the crank of 90˚. Next, based on the graph obtained for the velocity of the piston versus angle of the crank, the resulting line on the graph has the shape of sinusoidal. Furthermore, it can be observed that the velocity of the piston is at maximum when the angle of the crank is at 90˚ and the velocity of the piston is at minimum when the crank angle is at 270˚. Lastly, based on the graph obtained for acceleration of the piston against the angle of the crank, the shape
stationary point in its path. This type of motion, displays a single resonant frequency and sinusoidal in time.
3. The maximum velocity of the piston takes place at 90˚ because the velocity of the piston is perpendicular to the piston displacement at this particular point.
4. The increase in the ratio of the crank will certainly effect the displacement of the piston by the rod. As the length of the
connecting rod increases the displacement of the piston is shorter. However, the piston velocity and acceleration is not affected by the increase in ratio. Furthermore, as the ratio increases, simple
harmonic motion can be achieved.
5. Theoretically, the maximum piston acceleration should occur when the crank angle is at 180˚. However in this experiment, the
maximum piston acceleration occurs in between 10˚ and 40˚, it also occurs again at 360˚.
6. For the 115 mm and 175 mm rod length, the maximum acceleration
is at 0.9 mms-2. Whereas for the 130 mm rod length, the maximum
piston acceleration is at 1 mms-2
7. Maximum acceleration of piston and the velocity of the piston does not occur at the same angle in this experiment. However the piston acceleration is proportional to the piston velocity and this case can be authenticated by the simple harmonic motion.
Conclusion
In this experiment, we determined that the maximum piston displacement occurs at a crank angle of 90° where the piston velocity is perpendicular to this value. Therefore, the maximum velocity also occurs at a crank angle of 90°.
Overal the result that we have obtained are a sinusoidal graph with some fluctuating data from the error. Hence, the motion of these piston is a Simple Harmonic Motion. To achieve a more accurate Simple Harmonic
Motion, the ratio of the rod length and piston displacement should be increase.
From all these result and calculation, we found out that the maximum acceleration occurs between the crank angle of 10° and 40° as well as at 360°. So, the rod length of 115 mm and 175mm gives a maximum
acceleration of 0.9 mms-2, while rod length of 130mm give a maximum
acceleration of 1mms-2.
In conclusion, the acceleration of piston is proportional to the velocity of piston creating a Simple Harmonic Motion.
References
[1] Simple Harmonic Motion. 2009.
http://hyperphysics.phy-astr.gsu.edu/hbase/shm.html
[2] Introduction to Harmonic Motion. 2010.
https://www.khanacademy.org/science/physics/mechanical-waves-and- sound/simple-harmonic-motion-with-calculus/v/introduction-to-harmonic-motion
