An impact damper consisting of a steel pipe and a 20 lb (9 kg) steel shot-put was attached to the mast arm. The shot-put was confined within the pipe by steel plates. The total gap distance between the shot-put and steel plates was adjustable, allowing the damper to be tested at different gap widths. As with the Hapco damper, this damper relied on the impact to dissipate energy. The shot-put traveled the pipe's length, impacting the steel end plates. The impact damper's configuration could be changed by rotating the damper at 45-deg intervals allowing the device to be multi-directional and dampen the mast armÂ’s motion for both the in- and out-of-plane direction.