Foldable boom inner wings are attached to a boom center frame through a
rocker attached to a breakaway hydraulic cylinder pressurized to full
stroke and connected to an accumulator. When a wing impacts an object,
the impact load is transmitted through the fold cylinder and rocker into
the breakaway cylinder. As the breakaway cylinder retracts to allow the
wing to pivot, pressure builds in the system in three stages. First
pressure builds along an accumulator pressure curve until a relief valve
in the hydraulic system actives to initiate the second stage wherein oil
is dumped through the relief valve. Thereafter, pressure is again allowed
to build along the same accumulator curve to absorb impact hydraulically
before the cylinder reaches full stroke. The staged pressure buildup
prevents boom momentum from gaining and loads from increasing above the
strength of the overall structure.