Shock Absorbing Personal Load Operational Carriage System (SAPLOC System)

Abstract

This study details a novel approach to solve the problem of load carriage in military operations. The goal was to build a shock absorber into a rucksack to decrease the forces that are transmitted through the body and lower extremities while walking with a heavy pack. Soldiers often have overuse injuries like stress fractures, back problems, or joint pain during their careers and part of the cause is the heavy repetitive forces caused by walking with 80 plus pounds on their back. The SAPLOC System is a prototype that decouples the motion of the wearer’s body and the center of mass of the pack, much like a car’s suspension system, to reduce forces experienced by the body. The current prototype consists of a cylinder of aluminum to simulate the contents of a rucksack, a rod that it slides along, springs, and an aluminum for a surface the cylinder rubs against to act as a damper, all attached to an existing military surplus external rucksack frame. An accelerometer is attached to the oscillating mass and to the frame that is rigidly fixed to the body to deduce information about the coupling between the body and the load. Positive results from the accelerometers show that the system is not optimized, but it decreases the acceleration of the wearer compared to a fixed mass without a shock absorber in some situations, thus reducing the forces successfully. The current setup is not successful in reducing forces on level ground, but it generally is successful reducing forces going up and down stairs. From this conclusion future optimization and research into the concept is warranted.