Simpson 3D printer string calculator
Play with angle alpha (move the slider) to see the Simpson arm bend, and see the string length vary for the odd multipliers in some cases (X1ccw). This shows that the string anchors must be on the same side as the motor in order for the string length to be constant as alpha varies, for the ccw case only. This assumes pulleys of radius Pradius are mounted on the Simpson bolts, which are on a diameter at radius Bradius of the meshing gears (not shown) of radius Gradius. B and B' are the axes of the gears on the two arms. The effect of the meshing gears is here implicit in the reflection about the y axis. All these dimensions can be adjusted by the corresponding slider.
This has been modifed from the earlier version to handle both CW and CCW winding on the lower pulleys. The result is that the CW scheme has better symmetry and works best.