{"data":{"fields":"term_definition","term_definition":"<div class=\"definition\">Refers to a closed-loop (four-square) fatigue testing machine for endurace testing automotive and truck drive axles under load in a laboratory. The machine consists of a drive motor and reduction gear box driving the pinion of a test axle. The two axle shafts are coupled to one loop which drives the axle shaft of a second slave axle and thence the slave pinion which is coupled to the test pinion. A wind-up<\/div>"}}