function input_ex_rotor(; r = 1)

    # Copyright (C) 2021, Bruce Minaker
    #  Rotor stator model from D. Negrut and J.L. Ortiz, A practical approach for the linearisation of the constrained multibody dynamics equations, J. Comp. Nonlinear Dynam. 1 (2006), pp. 230â€“239.

    the_system = mbd_system("Rotor and stator")

    item = body("rotor")
    item.mass = 1300
    item.moments_of_inertia = [500, 500, 1000]
    item.products_of_inertia = [0, 0, 0]
    item.location = [0, 0, 0.75]
    item.velocity = [0, 0, 0]
    item.angular_velocity = [0, 0, r]
    add_item!(item, the_system)

    item = body("stator")
    item.mass = 200
    item.moments_of_inertia = [50, 50, 10]
    item.products_of_inertia = [0, 0, 0]
    item.location = [0, 0, 0]
    item.velocity = [0, 0, 0]
    item.angular_velocity = [0, 0, 0]
    add_item!(item, the_system)

    item = rigid_point("bearing")
    item.body[1] = "rotor"
    item.body[2] = "stator"
    item.location = [0, 0, 0]
    item.forces = 3
    item.moments = 2
    item.axis = [0, 0, 1]
    add_item!(item, the_system)

    item = flex_point("bushing")
    item.body[1] = "stator"
    item.body[2] = "ground"
    item.location = [0, 0, 0]
    item.forces = 3
    item.moments = 2
    item.axis = [0, 0, 1]
    item.stiffness = [1000, 10000]
    item.damping = [1, 10]
    add_item!(item, the_system)

    item = flex_point("bushing")
    item.body[1] = "stator"
    item.body[2] = "ground"
    item.location = [0, 0, 0]
    item.forces = 0
    item.moments = 1
    item.axis = [0, 0, 1]
    item.stiffness = [0, 100000]
    item.damping = [0, 100]
    add_item!(item, the_system)

    # Add some inputs and outputs
    item = sensor("kx")
    item.body[1] = "rotor"
    item.body[2] = "ground"
    item.location[1] = [0, 0, 0]
    item.location[2] = [0.1, 0, 0]
    item.gain = 1000
    item.units = "N"
    add_item!(item, the_system)

    item = sensor("ky")
    item.body[1] = "rotor"
    item.body[2] = "ground"
    item.location[1] = [0, 0, 0]
    item.location[2] = [0, 0.1, 0]
    item.gain = 1000
    item.units = "N"
    add_item!(item, the_system)

    item = sensor("kz")
    item.body[1] = "rotor"
    item.body[2] = "ground"
    item.location[1] = [0, 0, 0]
    item.location[2] = [0, 0, 0.1]
    item.gain = 1000
    item.units = "N"
    add_item!(item, the_system)

    item = actuator("X")
    item.body[1] = "rotor"
    item.body[2] = "ground"
    item.location[1] = [0, 0, 0]
    item.location[2] = [0.1, 0, 0]
    item.units = "N"
    add_item!(item, the_system)

    item = actuator("Z")
    item.body[1] = "rotor"
    item.body[2] = "ground"
    item.location[1] = [0, 0, 0]
    item.location[2] = [0, 0, 0.1]
    item.units = "N"
    add_item!(item, the_system)



    the_system

end
