When the lever contacts the follower-piece of the lid, it creates a closed-chain mechanism that can be modeled as an inverted crank-slider. Because the lever has non-trivial thickness and contacts different parts of the follower in each direction, the mechanisms have to be modeled separately. We will call the direction when the arm is being depressed the "Forward" direction, and the direction when the arm is moving up the "Backward" direction.

Forward Direction

In the forward direction, the mechanism can be modeled as a 4-bar crank slider as shown below:

Link 2 is the input crank, and it slides against link 3, which changes length as the crank rotates clockwise. Link 3 is rigidly coupled to link 4 (the lid) and offset by a fixed angle, leaving just one degree of freedom. Position and acceleration analysis can be seen below:

The input crank starts at 116 degrees and rotates clockwise to 73 degrees. These positions, along with link lengths and relative angles, were measured and calculated from images of the mechanism. The contact angles were found using the Bisection root-finding method, solving for when theta 4 was equal to 180 degrees. The kinematic values were only found during contact. Otherwise, theta 4 was set to 180 degrees and the acceleration of link 4 was set to 0.

From these plots we can see that the lid rotates clockwise so that the follower piece of the lid can move out of the way of the lever.

Backward Direction

In the backward direction , the mechanism can be modeled as a 5-bar crank slider as shown below:

Link 2A is the input crank, and is rigidly coupled to link 2B. Link 3 is rigidly coupled to link 4 (the lid) and offset by a fixed angle, again leaving just one degree of freedom. In this orientation, the end of link 3 slides against the edge of link 2B, meaning link 2B changes position. Position and acceleration analysis can be seen below:

The beginning and start angles are the reverse of the angles from the forward direction. The angle of the lid when contact ceases is similar to that found in the forward direction. However, the acceleration is much greater than the forward direction's acceleration. This is important because the coin is launched in the backward direction, so the lid has to continue opening past the point at which contact ceases.