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The LARC Vehicle
The LARC-5 (Lighter Amphibious Resupply Cargo) is an Army amphibious vehicle originally used in the 1960's to ferry supplies from ships to shore. Its total possible load is 5 tons (hence the five after LARC). Although no longer manufactured, all three sizes LARC-5, LARC-15, and LARC-60's still see service both within and outside the military.
The Hydro-LARC
The Mechanical LARC-5
Click to view a LARC Video.
Movie viewers may be obtained from www.real.com.
The FRF's Hydro-LARC is so named because it has been modified from the original
transmission, gear propeller, and drive shaft to a hydraulic fluid drive
system. The Caterpillar 3106 turbo diesel engine is a 6-cylinder 223 kW (300 hp)
engine that transfers hydraulic fluid at 5515 kPa (800psi) or higher to hydraulic
motors that power all four of the wheels, the propeller, power steering, brakes,
and bilge pumps. The variable stroke feature of the pump allows an infinitely
variable gear ratio in either forward or reverse and constant engine speed.
The conversion to hydraulic power was done to increase reliability and performance.
The maximum speed of the LARC on land is 40 km/hr (25 mph) and approximately
11 km/hr (6 knots) in water. Surveying is typically conducted at a speed of 7 km/hr
(4 knots), however, the speed of the Hydro-LARC is adjusted according to wave conditions
to obtain optimal data quality . The typical offshore operating range
of the LARC is 8 km (5 miles). The LARC is 10.6 m (35 ft) long,
3 m (10.2ft) wide, and 3.3 m (11 ft) tall. For use outside of the immediate vicinity
of the FRF, the LARC is loaded on a flat-bed trailer and hauled to the site.
To support survey operations, the operator's cab has been enlarged to provide space
for the survey equipment and two additional personnel in a climate controlled environment.
AC power for the survey equipment is supplied by a 5.2 kW (7 hp) diesel generator mounted
below the deck of the vehicle. The generated AC power passes through a power
conditioner and into a non-ferrous uninterrupted power source (UPS). The UPS
output then feeds power to the survey equipment. This generator also powers
the cabin air conditioning unit.
The FRF also operates a second, mechanical drive LARC. The second LARC is used for
other tasks such as to deploy instruments, support diving activities, collect data,
lay underwater cables and to tow a variety of sensors. An onboard davit and winch
can lift 400 kg (900 lbs). A portable shed can be set on the open deck to support
the electronics requirements of any type of sensor. The Army used the LARC to ferry
supplies from boats to shore; when purchased by the FRF, the LARC was military surplus.
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