2.2.1. Calculation of the Shaft Diameter

This parameter was obtained by carrying out a simplification. Since the machines under examination are generally subjected to low stresses, only the torsion to which the shaft is subjected was taken into consideration [37]. Considering *τa*, the maximum allowable tension of the material of which the shaft is composed, and *Pe*, the maximum power that is reached at the axis of the machine, the shaft diameter was obtained as follows:

$$d\_{\rm slf} = \left(\frac{16P\_{\rm c}}{\omega \pi \tau \tau\_{\rm a}}\right)^{\frac{1}{3}} \tag{31}$$

Since it is not always possible to know the value of the admissible voltage for each pump under analysis whose constituent material is known, the value obtained to which reference will be made in the maximum calculations was an average value equal to 7.56 Mpa [37].
