Bennett 4R mechanism

It is Bennett 4R mechanism (not spherical 4R mechanism)

4R: 4 revolute joints. It does not meet Kutzbach criterion.

The conditions that the mechanism must satisfy to be able to move:

1. The opposite sides of the mechanism (i.e. links that are not concurrent) have the same lengths, denoted by a, b.

2. The angles of twist are denoted by A, B and they are equal on opposite sides but with different sign.

3. The link lengths and link twist angles must satisfy the relation: sinA/a = sinB/b

For the blue and yellow (fixed) link: a = 17.599, A= 15 deg.

For the orange and green link: b= 34, A= 30 deg.