The conventional spider arm is in 100% contact between the driver jaw & the driven jaw, even at no load condition. Obviously, when torque is applied, the resultant force extrudes the elastomeric material of the spider only in the outward direction. Depending upon the torque fluctuations and the misalignment forces, there is a continuous abraised movement of the spider arm against the entire surface of the jaws which causes substantial heat build up due to friction & results into fracture of the molecular links in the spider which causes its failure.

The new NENFLEX spiders, the star shaped, the wrap around & the individual free floating drive insets have a special profile which allows only a partial contact of the spider arm with the coupling jaws, at no load. When torque is applied, the entire surface of the spider arm comes into contact with the driver & the driven jaws as illustrated in Fig. 1 & 2. There is less abrasion & heat build up because of the easier deformation of the spider arm, by virtue of the space available as marked by the small arrows.