Experiments on flow-induced vibrations using a close-packed triangular rod array with a pitch-to-diameter ratio of 1.1 in water cross-flow was carried out and data analysis performed. The bundle consists of 21 rows with five rods in each. One flexibly mounted test rod (TR) is located in the fourth row in an otherwise fixed array. The rod can freely move in the transverse and in-line direction. Two accelerometer sensors were attached at the both ends of the TR to measure the rod response on the fluid flow. Kalman type filters was used in order to restore TR kinematics from simultaneous measurements of accelerometers and less sensitive laser extensometers. The effect of Reynolds number on the stability of the flexibly mounted TR has been analysed. Flow history (different flow increasing and decreasing scenarios) impact on the stability of TR oscillating motion was studied as well.