I need to find the mobility of the pictured system I have labeled the 5 links with black numbers and the 6 joints with red letters for convenience Attempt at a solution: I know the mobility equation is M = 3(N-1) – 2(J1) – J2 + R, where N = number of links, J1 is the number of 1 DoF Joints, J2 is the number of 2 DoF joints and R is the number of redundancies. So far, I have 5 links (where 1 is the ground and 4 is the entire disk), 5 1 DoF joints (A, C, D rolling without slipping, E & F), and one 2 DoF joints (B, a 2 DoF slider). Plugging that into the mobility equation yields 3(5-1) – 2(5) – 1 = 12 – 10 – 1 = 1 However, upon inspection, the system has 2 degrees of freedom and not 1 as the mobility equation suggests. I have been trying to reason through where I may have went wrong, or if there are any redundancies in the system to no avail. Any help would be appreciated.