a biasing element 88 such as a helical spring is provided between the flange 82 and a seat 86 to apply a biasing force to the coupling member 66 in a direction away from the input shaft 26 at undesirably high temperatures the thermal coupling material melts which permits the biasing element 88 to urge the coupling member 66 away from the input shaft 26 such that the dog teeth 68 are separated from one another to provide the gap 89 as shown in fig5 in one example the thermal coupling 84 is provided by a eutectic solder material of 91 3 tin and 8 7 zinc by weight for example this composition melts at 390 u00b0 f 199 u00b0 c the thermal coupling 84 exhibits good creep characteristics for example about 4 4 times high compressive stress capability and 49 times longer life for the same operating parameters than the previous thermal coupling material that melted at 354 u00b0 f 179 u00b0 c the input shaft 26 includes splines 91 at one end which engage with corresponding structure of the accessory drive gearbox 14 the dog teeth 68 are arranged at the opposite end of the shaft relative to the splines 91 an intermediate region of the input shaft 26 includes a weakened area 90 provided by an arcuate groove circumscribing an outer diameter of the input shaft 26 the weakened area 90 is designed to break at a particular torque to prevent damage to the accessory drive box 14 and engine 12 the weakened area 90 includes a diameter 94 which may be 0 559 inch 1 42 cm nominally at a nominal 40 hrc the input shaft 26 has a shear torque in lbs to.