TM 5-5420-278-100003 000003 00-1DESCRIPTION AND THEORY OF OPERATIONIMPROVED RIBBON BRIDGE (IRB)RAMP BAY M16NSN 5420-01-470-5825 P/N 12478918;INTERIOR BAY M17NSN 5420-01-470-5824 P/N 12478919.Section I. EQUIPMENT DESCRIPTION AND DATAEQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURESThe Improved Ribbon Bridge (IRB) is a modular bridge having a roadwaysurface supported by a floating integral superstructure made of aluminum thatfunctions as a ponton. A complete ribbon bridge consists of a ramp bay at each bankand the required number of connected interior bays spanning between them. TheIRB 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 inWP 0036 00. The IRB can be used for rafting operations by using one or moreinterior bays joined with a ramp bay at each end. An IRB bay is retrievable in fiveminutes or less. Each bay is transported, launched, and retrieved in a foldedcondition on a ribbon bridge transporter.IRB Interior Bay (IRB-I). The IRB-I is a four-ponton folding module consistingof two roadway pontons and two bow pontons. Each inner ponton is divided into twowatertight compartments. The IRB-I unfolds automatically once released and afloat.IRBs are connected to each other by manually engaging two lockpins and latches onthe roadway pontons. The lockpins act as bearing points between consecutivelyjoined bays, thus allowing the entire bridge to hinge with the weight of a movingvehicle and uneven water conditions.IRB Ramp Bay (IRB-R). The IRB-R is a four-ponton module that functionssimilar to the IRB-I, but differs substantially in design. The ramp end of theroadway pontons extends lengthwise, beyond the bow pontons, and slopes down,forming the ramp edge. The sides of the bow pontons are slightly tapered towardthe ramp end, and attaching extensions called ramp plates are provided. The IRB-Rcontains a manually controlled raising mechanism that works against the end andweight of an adjoining IRB-I. The angle or height of the IRB-R can be adjusted tomeet various bank conditions. The IRB-R also contains two large stowage boxesrecessed in the outer pontons.The Common Bridge Transporter (CBT) M1977. The CBT consists of aremanufactured 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 removableflatrack that is loaded on the CBT by the LHS, and is used in conjuction with theLHS to load, unload, and transport interior and ramp bays.
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