The boom is a three section 27 to 70 ft (8.2 to 21.3
the sections. The boom nose consists of five
m) cable extended boom.
sheaves (two upper and three lower), mounted on
heavy duty tapered roller bearings and utilizes pin-
The boom is trapezoidal in design and utilizes one
type guards to allow easy reeving.
heavy duty 5.5 in. (13.9 cm) telescope cylinder. The
telescoping sections are supported on graphite
Boom assembly lift is provided by one heavy duty
impregnated nylatron wear pads. Adjustable side
7.5 in. (18.9 cm) diameter bore lift cylinder. Boom
wear pads prevent metal-to-metal contact between
elevation is from -3 to 78 degrees.
THEORY OF OPERATION
the sheaves at the end of the telescope cylinder
push on the four extension cables. This causes the
The rod end of the telescope cylinder is secured to
extension cables to pull the fly section out at the
the boom base section and the cylinder barrel is
same time and rate that the telescope cylinder is
secured to the mid section. The four extension
pulling out the mid section.
cables are secured to the boom base section, routed
around four sheaves at the barrel end of the
telescope cylinder, and secured at the opposite end
to the fly section. The retraction cable is secured at
As the telescope cylinder is retracted, the mid
the outside front of the base section, routed around a
section, which is attached to the cylinder barrel, is
sheave mounted on the end of the mid section, and
pulled in. At the same time, the sheave at the rear of
secured at the opposite end to the fly section.
the mid section pushes on the retraction cable. This
causes the retraction cable to pull the fly section in at
As the telescope cylinder extends, the cylinder
the same time and rate that the telescope cylinder is
barrel, which is attached to the mid section, pulls the
pulling in the mid section.
mid section out along with it. At the same time,