Answer :
Below is an image of a design of a fourbar Grashof crank-rocker to give 45° of rocker rotation with equal time forward and back, from a constant speed motor input.
Below is the steps on how to make the design:
1. Draw the output link [tex]\( O_4B \)[/tex] in its extreme positions [tex]\( B_1 \)[/tex] and [tex]\( B_2 \)[/tex], subtending the desired angle at [tex]\( O_4 \)[/tex].
2. Draw and extend the chord [tex]\( B_1B_2 \)[/tex].
3. Select a convenient point [tex]\( O_2 \)[/tex] on the extended [tex]\( B_1B_2 \)[/tex].
4. Bisect [tex]\( B_1B_2 \)[/tex] and draw a circle with this radius centered at [tex]\( O_2 \)[/tex].
5. Label the circle's intersections with \( B_1B_2 \) extended as \( A_1 \) and [tex]\( A_2 \)[/tex].
6. Measure the coupler length from[tex]\( A_1 \) to \( B_1 \) or \( A_2 \) to \( B_2 \).[/tex]
7. Measure the ground length (link 1), crank length (link 2), and rocker length (link 4).
8. Check the Grashof condition. If non-Grashof, move [tex]\( O_2 \)[/tex] farther from [tex]\( O_4 \)[/tex]and repeat.
9. Lastly, build a model and check its function and transmission angles.
