gripper rolls along the curved member 44 furthermore this particular guide is an example of a structural element that has been incorporated into the machine frame 46 the elongated curved member forming the illustrated guide has been welded to the frame the machine frame transmits from the load bearing drive shafts 14 at the top of the frame which are drive by hydraulic motors 48 to pivot and load cell points 48 and 50 respectively at the bottom by combining load carrying with chain guide the frame 46 reduces or minimizes the space and mass requirements of both functions referring to fig6 a and 6b each chain loop 12 of an injector head such as the ones shown in fig1 5 comprises a flexible tensile member with distributed mass it maintains a constant tensile force at any point throughout its entire length if the member is of constant section and material it will have its mass evenly distributed along its length the chain will have a resistance to bending but this may be very low the combination of such a member 39 s mass flexibility length and tension together provide the mechanism for oscillation higher mass and greater length reduce the frequency of oscillation higher tension increases it once induced an oscillation in such a system will persist until its.