than others in particular titanium is abrasive and may wear through other contacting materials if subjected to sufficient stress the coating 40 minimizes wear from twisting bending and other deformation as well as from friction the assembly 11 includes more than one spring so each individual spring can have a lower mass as strength from multiple springs is combined as a result of the lower mass of each individual spring in the system the dual spring embodiment has a higher intrinsic natural frequency this higher natural frequency adds safety as the frequency is out of the range of frequencies experienced in use when the apparatus experiences frequencies similar to its natural frequency it can more easily fail this has been seen in airplane landing gear because the natural frequency of the system is higher a measure of safety is added returning to the end mounts 18 the inner diameter of the grooves 28 in end mounts 18 is slightly larger than the resting coil diameter of the outer spring 16 for this reason coupled with the fact that the mentioned springs are tension springs as the spring is introduced to tension the spring diameter naturally tends to decrease however the end mount 18 forces the coil diameter to remain the same on.