DESCRIPTION AND THEORY OF OPERATION
IMPROVED RIBBON BRIDGE (IRB)
RAMP BAY M16
NSN 5420-01-470-5825 P/N 12478918;
INTERIOR BAY M17
NSN 5420-01-470-5824 P/N 12478919.
Section I. EQUIPMENT DESCRIPTION AND DATA
EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES
The Improved Ribbon Bridge (IRB) is a modular bridge having a roadway
surface supported by a floating integral superstructure made of aluminum that
functions as a ponton. A complete ribbon bridge consists of a ramp bay at each bank
and the required number of connected interior bays spanning between them. The
IRB has a roadway width of 14 ft 9 in. (4.5 m). Adjacent to the roadway is a 4 ft
(1.2 m) walkway on the bow pontons. IRB crossing weight capacities are listed in
WP 0036 00. The IRB can be used for rafting operations by using one or more
interior bays joined with a ramp bay at each end. An IRB bay is retrievable in five
minutes or less. Each bay is transported, launched, and retrieved in a folded
condition on a ribbon bridge transporter.
IRB Interior Bay (IRB-I). The IRB-I is a four-ponton folding module consisting
of two roadway pontons and two bow pontons. Each inner ponton is divided into two
watertight compartments. The IRB-I unfolds automatically once released and afloat.
IRBs are connected to each other by manually engaging two lockpins and latches on
the roadway pontons. The lockpins act as bearing points between consecutively
joined bays, thus allowing the entire bridge to hinge with the weight of a moving
vehicle and uneven water conditions.
IRB Ramp Bay (IRB-R). The IRB-R is a four-ponton module that functions
similar to the IRB-I, but differs substantially in design. The ramp end of the
roadway pontons extends lengthwise, beyond the bow pontons, and slopes down,
forming the ramp edge. The sides of the bow pontons are slightly tapered toward
the ramp end, and attaching extensions called ramp plates are provided. The IRB-R
contains a manually controlled raising mechanism that works against the end and
weight of an adjoining IRB-I. The angle or height of the IRB-R can be adjusted to
meet various bank conditions. The IRB-R also contains two large stowage boxes
recessed in the outer pontons.
The Common Bridge Transporter (CBT) M1977. The CBT consists of a
remanufactured and modified Heavy Expanded Mobility Tactical Truck (HEMTT)
M977 and a Load Handling System (LHS) which together are called the CBT or
Transporter. The Bridge Adapter Pallet (BAP) M15 is a separate removable
flatrack that is loaded on the CBT by the LHS, and is used in conjuction with the
LHS to load, unload, and transport interior and ramp bays.