OF DESIGN MACHINERY
SOLUTION MANUAL 3-3-1
PROBLEM 3-3 Statement: Design a fourbar mechanism to give the two positions shown in Figure P3-1 of output rocker motion with no quick-return. (See Example 3-2.) Build a cardboard model and determine the toggle positions and the minimum transmission angle. Coordinates of A1, B1, A2, and B2 (with respect to A1): x A1 0.00 yA1 0.00 Solution: x B1 1.721 yB1 1.750 x A2 2.656 yA2 0.751 x B2 5.065 yB2 0.281
Given:
See Figure P3-1 and Mathcad file P0303. Link length: Link 3 L3 5.000 Link 4 L4 2.000
Design choices: 1.
Following the notation used in Example 3-2 and Figure 3-5, change the labels on points A and B in Figure P3-1 to C and D, respectively. Draw the link CD in its two desired positions, C 1D1 and C 2D2, using the given coordinates. Draw construction lines from C1 to C 2 and D1 to D2. Bisect line C 1C 2 and line D1D2 and extend their perpendicular bisectors to intersect at O4. Using the length of link 4 (design choice) as a radius, draw an arc about O4 to intersect both lines O4C1 and O4C 2. Label the intersections and B1 B2. Draw the chord B1B2 and extend it in any convenient direction. In this solution it was extended to the left. Layout the distance A1B1 along extended line B1B2 equal to the length of link 3. Mark the point A1. Bisect the line segment B1B2 and layout the length of that radius from point A1 along extended line B1B2. Mark the resulting point O2 and draw a circle of radius O2A1 with center at O2. Label the other intersection of the circle and extended line B1B2, A2. Measure the length of the crank (link 2) as O2A1 or O2A2. From the graphical solution, L2 0.9469
2. 3. 4. 5. 6. 7. 8. 9.
10. Measure the length of the ground link (link 1) as O2O4...