Scotch Yoke, Slotted Link, Withworth Return Mechanism

2314 Words May 9th, 2013 10 Pages
EXPERIMENT 4.1 – SCOTCH YOKE MECHANISM

BACKGROUND OF STUDY:
Pure simple harmonic motion is produced by the Scotch Yoke mechanism when driven by an eccentric or crank.
Its early application was on steam pumps but it is not suitable for high speeds due to the backlash in the scotch yoke. It is now mainly used in computing type applications where harmonic motion is required.
The Scotch yoke is a mechanism for converting the linear motion of a slider into rotational motion or vice-versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part. The shape of the motion of the piston is a pure sine wave over time given a constant rotational speed.
This setup is most
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.5 | 16.75 | 80 | 21 | 21 | 21 | 90 | 25.5 | 25 | 25.25 | 100 | 30 | 29 | 29.5 | 110 | 34 | 33.5 | 33.75 | 120 | 38 | 37.5 | 37.75 | 130 | 41.5 | 41.5 | 41.5 | 140 | 44.5 | 44.5 | 44.5 | 150 | 47 | 47 | 47 | 160 | 49 | 49 | 49 | 170 | 50 | 50 | 50 | 180 | 50 | 50 | 50 | 190 | 50 | 50 | 50 | 200 | 49 | 49 | 49 | 210 | 47 | 47 | 47 | 220 | 44.5 | 44.5 | 44.5 | 230 | 41.5 | 41.5 | 41.5 | 240 | 37.5 | 38 | 37.75 | 250 | 33.5 | 34 | 33.75 | 260 | 29 | 30 | 29.5 | 270 | 25 | 25.5 | 25.25 | 280 | 21 | 21 | 21 | 290 | 16.5 | 17 | 16.75 | 300 | 12.5 | 13 | 12.75 | 310 | 9 | 9.5 | 9.25 | 320 | 5 | 6 | 5.5 | 330 | 4 | 4 | 4 | 340 | 2 | 2 | 2 | 350 | 0.5 | 1 | 0.75 | 360 | 0 | 0 | 0 |
Table 1 – Scotch Yoke Mechanism Experimental Data
Graph

Theoretical data
Theoretically:
x=r (1-cosθ)
Where: x is average linear displacement (mm) r is radius (mm) θ is crank angle (⁰)
Given: r = 25mm
From the formula, we calculate this theoretical data: Angle, θ (⁰) | Average Linear Displacement, x (mm) | 0 | 0 | 10 | 0.38 | 20 | 1.51 | 30 | 3.35 | 40 | 5.85 | 50 | 8.93 | 60 | 12.5 | 70 | 16.4 | 80 | 20.66 | 90 | 25 | 100 | 29.34 | 110 | 33.55 | 120 | 37.5 | 130 | 41.07 | 140 | 44.15 | 150 | 46.65 | 160 | 48.49 | 170 | 49.62 | 180 | 50 | 190 | 49.62 | 200 | 48.49 | 210 | 46.65 | 220 | 44.15 | 230 | 41.07 | 240 | 37.5 | 250 | 33.55 | 260 | 29.34 | 270 | 25 | 280 | 20.66 | 290 | 16.45 | 300 | 12.5 | 310 | 8.93 | 320 | 5.85 | 330 | 3.35 |

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