FAP-M Flexible Shaft

Flexible shafts are mechanical elements which are subject to torque and undergo a rotational elastic deformation.

Considering a single flexible shaft, the equal and opposite torques which are applied at each extremity cause a relative rotation of the various sections which is proportional to the distance between the sections.

Parameter r = 1 when the shaft is loaded according to the winding direction of the spiral; r < 1, when the shaft is loaded according to the opposite direction of the spiral, as indicated in the following table:

The relation between Applied Torque T [Nm] and Twist Angle of the segments φ [°] is a function of three parameters as follows:

● Torsional Rigidity k [103Nm/°] which depends on the section diameter and its construction characteristics

● Length of the shaft L [mm]

● Rotation Direction r (dimensionless parameter which characterizes the asymmetric behavior of the shaft)

The figure shows a qualitative-quantitative curve of the efficiency of the flexible shaft as a function of the bending radius. For configurations which are almost in a straight line, the efficiency is equal to the maximum value 0.9. The efficiency is nearly constant for high values of the bending radius and decreases rapidly down to 0.2 as the minimum bending radius is approached.