Grashof Condition

For my end goal, I needed a mechanism that could by continuously rotated at a constant angular velocity. To satisfy this requirement, I used the Grashof equation for my mechanism by thinking of my mechanism as two four bar linkages.

L + S < Q + P (Grashof Equation)

This tells us that if the longest and shortest link lengths are less than the remaining link lengths, the linkage is a Class 1 case. Therefore the linkage has one grounded link that can rotate fully. To ensure that my input link could rotate fully, I adjusted the link lengths such that the four bar linkage satisfied the Grashof condition.

Figure 1: First four bar linkage Figure 2: Second four bar linkage

Prototyping

Initial prototypes of the mechanism were made of LEGOs, until desired design was achieved.

Figure 3: Joint Assembly

Laser Cutting and Materials

After optimal design was reached, measurements were taken and further prototypes were made with wood, washers, and screws. For further prototypes, height was added to final mechanism design to help achieve the goal of using the mechanism as a crusher. Links and frames were made by laser cutting 1/4" wood. 5/16" wooden rod and washers were used to create joints between links allowing free rotational movement between joints. Screws were used to place frame on plywood base. After prototyping with wood, conclusion was reached to reduce size of slider to reduce weight so coupler link would not break. Below is a figure containing all laser cut pieces.

Figure 4: Pieces cut by laser cutter

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