for all curves; curve 1, ξ=0.3; curve 2, ξ=0.6; curve 3, ξ=0.8.

Upon turning to Figure 2(b) and recalling that nonmetallic belts under tension stretch over time, it is clear that whenever these belts are used, the tension on them will increase as the angle θ decreases due to the belt’s stretching. Hence, the motor must be moved periodically if the tension is to remain within narrow limits.