last equation 11 establishes a figure of merit for such tension actuators in order to generate larger forces for a given applied fluid pressure 34 the desire is to achieve the greatest change in effective displacement for each given incremental contraction over the full range of operation the total effective volumetric displacement over the full stroke length is calculated by the total area under the curve to be 0 40 cubic inches in the actuator 20b shown in fig8 and 9 there are five pairs of the tension strands 26 oriented at a pitch angle of 72 u00b0 the double row of small circles 46 schematically indicate the keyhole shaped slots 46 fig5 in the existing end fittings 22 which have already been described thus as seen in order to achieve a pitch angle of 72 u00b0 the continuous strand which is used to produce the five pairs of strands 26 is laced through every fourth one of the twenty slots 46 the anchoring points 28 are indicated it is noted that a single crossing point 62 between each two neighboring struds and located exactly at the mid length of the strands 26 is achieved when the number of pairs of strands is sufficiently small that equ5 the total number of crossing points 62 is five but only three are seen in fig8 because the other two are located on the other side of the elastomeric shell 24 in the actuator 20c shown in.