An injector head unit comprising: one or more drive chains revolving within a common plane mounted on an upper drive sprocket and a lower drive sprocket, and a movable bearing housing associated with one of the upper and lower drive sprockets, A. wherein at least one of the upper and lower drive sprockets are configured to move vertically to tension the drive chains; and further comprising: at least one fixed reference point proximate to at least one of the upper and lower drive sprockets, wherein the at least one fixed reference point indicates a percentage elongation of the drive chains relative to an original drive chain length, wherein relative positioning of one of the movable upper and lower drive sprockets with the fixed reference point indicates to a user an amount of elongation of the drive chains after a certain period of time; or B. wherein the lower drive sprocket is configured to move vertically to tension the drive chains; further comprising: one or more fixed reference points (122a, 122b, 122c) proximate to the movable lower drive sprocket, wherein the fixed reference points (122a, 122b, 122c) indicate a percentage elongation of the drive chains relative to an original drive chain length; and a reference point on the lower drive sprocket configured to move relative to the one or more fixed reference points (122a, 122b, 122c), wherein relative positioning between the lower drive sprocket reference point and the fixed reference points (122a, 122b, 122c) indicates to a user an amount of elongation of the drive chains during operation. one or more drive chains revolving within a common plane mounted on an upper drive sprocket and a lower drive sprocket, and a movable bearing housing associated with one of the upper and lower drive sprockets, A. wherein at least one of the upper and lower drive sprockets are configured to move vertically to tension the drive chains; and further comprising: at least one fixed reference point proximate to at least one of the upper and lower drive sprockets, wherein the at least one fixed reference point indicates a percentage elongation of the drive chains relative to an original drive chain length, wherein relative positioning of one of the movable upper and lower drive sprockets with the fixed reference point indicates to a user an amount of elongation of the drive chains after a certain period of time; or B. wherein the lower drive sprocket is configured to move vertically to tension the drive chains; further comprising: one or more fixed reference points (122a, 122b, 122c) proximate to the movable lower drive sprocket, wherein the fixed reference points (122a, 122b, 122c) indicate a percentage elongation of the drive chains relative to an original drive chain length; and a reference point on the lower drive sprocket configured to move relative to the one or more fixed reference points (122a, 122b, 122c), wherein relative positioning between the lower drive sprocket reference point and the fixed reference points (122a, 122b, 122c) indicates to a user an amount of elongation of the drive chains during operation. A. wherein at least one of the upper and lower drive sprockets are configured to move vertically to tension the drive chains; and further comprising: at least one fixed reference point proximate to at least one of the upper and lower drive sprockets, wherein the at least one fixed reference point indicates a percentage elongation of the drive chains relative to an original drive chain length, wherein relative positioning of one of the movable upper and lower drive sprockets with the fixed reference point indicates to a user an amount of elongation of the drive chains after a certain period of time; or at least one fixed reference point proximate to at least one of the upper and lower drive sprockets, wherein the at least one fixed reference point indicates a percentage elongation of the drive chains relative to an original drive chain length, wherein relative positioning of one of the movable upper and lower drive sprockets with the fixed reference point indicates to a user an amount of elongation of the drive chains after a certain period of time; or B. wherein the lower drive sprocket is configured to move vertically to tension the drive chains; further comprising: one or more fixed reference points (122a, 122b, 122c) proximate to the movable lower drive sprocket, wherein the fixed reference points (122a, 122b, 122c) indicate a percentage elongation of the drive chains relative to an original drive chain length; and a reference point on the lower drive sprocket configured to move relative to the one or more fixed reference points (122a, 122b, 122c), wherein relative positioning between the lower drive sprocket reference point and the fixed reference points (122a, 122b, 122c) indicates to a user an amount of elongation of the drive chains during operation. one or more fixed reference points (122a, 122b, 122c) proximate to the movable lower drive sprocket, wherein the fixed reference points (122a, 122b, 122c) indicate a percentage elongation of the drive chains relative to an original drive chain length; and a reference point on the lower drive sprocket configured to move relative to the one or more fixed reference points (122a, 122b, 122c), wherein relative positioning between the lower drive sprocket reference point and the fixed reference points (122a, 122b, 122c) indicates to a user an amount of elongation of the drive chains during operation.