A rail vehicle for movement along a track having a longitudinal axis, comprising: a frame ; a carriage assembly operatively coupled to the frame ; and at least one workhead coupled to the carriage assembly , the workhead having a jaw member for removing rail spikes ; a mechanical detector coupled to the carriage assembly , the mechanical detector being operable to move from a first, disengaged position in which the mechanical detector is parallel or oblique to the longitudinal axis of the track as measured along a stem portion of the mechanical detector , to a second, engaged position in which the mechanical detector is substantially orthogonal to the longitudinal axis of the track as measured along the stem portion of the mechanical detector , wherein the mechanical detector is operable to detect a tie when in the second, engaged position; a hydraulic cylinder operably coupled to the mechanical detector through a coupling assembly and configured to rotate the mechanical detector between the first and second positions; and an onboard computing system operable to receive a signal when the tie is detected and cause the carriage assembly to lower into position adjacent a rail spike ; a pair of guide rods coupled to the frame ; and a subframe member including a plurality of connectors , wherein the carriage assembly is operatively coupled to the frame via the subframe member and the guide rods , and the plurality of connectors receive the guide rods in cavities defined by the connectors , wherein the subframe member is operable to move along the guide rods in a longitudinal direction for longitudinal displacement of the carriage assembly along and relative to the frame . a frame ; a carriage assembly operatively coupled to the frame ; and at least one workhead coupled to the carriage assembly , the workhead having a jaw member for removing rail spikes ; a mechanical detector coupled to the carriage assembly , the mechanical detector being operable to move from a first, disengaged position in which the mechanical detector is parallel or oblique to the longitudinal axis of the track as measured along a stem portion of the mechanical detector , to a second, engaged position in which the mechanical detector is substantially orthogonal to the longitudinal axis of the track as measured along the stem portion of the mechanical detector , wherein the mechanical detector is operable to detect a tie when in the second, engaged position; a hydraulic cylinder operably coupled to the mechanical detector through a coupling assembly and configured to rotate the mechanical detector between the first and second positions; and an onboard computing system operable to receive a signal when the tie is detected and cause the carriage assembly to lower into position adjacent a rail spike ; a pair of guide rods coupled to the frame ; and a subframe member including a plurality of connectors , wherein the carriage assembly is operatively coupled to the frame via the subframe member and the guide rods , and the plurality of connectors receive the guide rods in cavities defined by the connectors , wherein the subframe member is operable to move along the guide rods in a longitudinal direction for longitudinal displacement of the carriage assembly along and relative to the frame . <EOS>