The vibraphone frame offers a number of challenges to designers. It must be sturdy enough to endure the torsional forces created by the damper/spring/pedal assembly and the stresses of repeated transport and playing, while still being light enough for easy transport. Considering the weight of the bars alone, this does not leave much margin for the frame. The bars must also be securely attached to the frame, but not rigidly. Each bar must have some independent flex for it to ring.