A shaft mounting assembly comprising: an elongate shaft comprising an outer surface having a substantially circular cross-section; a cylinder having an inner surface defining a bore, the bore housing the shaft, wherein the inner diameter of the cylinder is larger than the outer diameter of the shaft such that a gap is defined between the outer surface of the shaft and the inner surface of the cylinder; and, a spring comprising a substantially circular discontinuous band; wherein one of the outer surface of the shaft and the inner surface of the cylinder comprises a groove; and wherein the groove extends around the circumference of the outer surface of the shaft or the circumference of the inner surface of the cylinder respectively; wherein the spring is positioned in the groove such that both axial edges of the band are located within the groove; and, wherein the spring has a de-energised state in which the height of the band is greater than the depth of the groove, so that a portion of the band between the axial edges protrudes out of the groove, and the axial width of the band is less than the width of the groove; and, an energised state in which the spring is compressed within the bore such that the height of the band is reduced, and the axial width of the band is increased compared to the de-energised state; and wherein the substantially circular discontinuous band of the spring has correspondingly shaped axially arcuate inner and outer surfaces; and the axial width of the band is less than the width of the groove in the energised state; wherein the shaft is a static piston which is housed in the cylinder so as to be non-reciprocatable and non-rotatable relative to the cylinder. an elongate shaft comprising an outer surface having a substantially circular cross-section; a cylinder having an inner surface defining a bore, the bore housing the shaft, wherein the inner diameter of the cylinder is larger than the outer diameter of the shaft such that a gap is defined between the outer surface of the shaft and the inner surface of the cylinder; and, a spring comprising a substantially circular discontinuous band; wherein one of the outer surface of the shaft and the inner surface of the cylinder comprises a groove; and wherein the groove extends around the circumference of the outer surface of the shaft or the circumference of the inner surface of the cylinder respectively; wherein the spring is positioned in the groove such that both axial edges of the band are located within the groove; and, wherein the spring has a de-energised state in which the height of the band is greater than the depth of the groove, so that a portion of the band between the axial edges protrudes out of the groove, and the axial width of the band is less than the width of the groove; and, an energised state in which the spring is compressed within the bore such that the height of the band is reduced, and the axial width of the band is increased compared to the de-energised state; and wherein the substantially circular discontinuous band of the spring has correspondingly shaped axially arcuate inner and outer surfaces; and the axial width of the band is less than the width of the groove in the energised state; wherein the shaft is a static piston which is housed in the cylinder so as to be non-reciprocatable and non-rotatable relative to the cylinder.