pts Due: Wed, February 8th, at the start of class, Paper copies only -No electro

Question

pts Due: Wed, February 8th, at the start of class, Paper copies only -No electronic submissions Problem 1. Figure 1 on the next page shows the three prescribed positions for a wing landing gear. Design a four bar linkage that will move the landing gear thru all three positions. The moving pivots must be connected to the wheel support member and the ground pivots must be within the air frame. Add a dyad driver to the linkage with a time ratio of 1.3 (Where 1.3-time going down time coming up.) For this problem only; make two drawings, one drawing showing all layout and construction lines and calculations; and another drawing with the final design showing the linkage in one position only Problem 2.) Figure 2 on the following page shows a movable shelf and cabinet. Graphically synthesize a linkage to guide the shelf through the 3 positions shown. The first position is level with the top of the cabinet and the third position is a stored position for inside the cabinet. Ground pivots should fall within the cabinet and the linkage size should be minimized to take up the least amount of cabinet space. Find acceptable locations for the ground and

Explanation / Answer

The four bar linkage is the simplest mechanism composed of rigid bodies and lower pairs is called a linkage . In planar mechanisms, there are only two kinds of lower pairs --- revolute pairs and prismatic pairs.

Some important concepts in link mechanisms are:

In a four-bar linkage, we refer to the line segment between hinges on a given link as a bar where:

Grashof's theorem states that a four-bar mechanism has at least one revolving link if

s + l <= p + q

and all three mobile links will rock if

s+ l > p + q

The inequality 5-1 is Grashof's criterion.

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