Fifth-Wheel Load Transducer
The UMTRI fifth-wheel load transducer was created by UMTRI for NHTSA and is the property of NHTSA. UMTRI serves as NHTSA's agent in making the device available for use by the motor vehicle industry for appropriate testing purposes.
The transducer is intended to measure all four primary loads that are transmitted between tractor and semitrailer by the fifth-wheel coupling, namely, longitudinal force, Fx, lateral force, Fy, vertical force, Fz, and roll moment, Mx. The transducer system measures these loads by replacing the standard fifth-wheel chairs with specially-made chairs, each of which is, itself, a four-component load transducer. The four signals from the individual chairs are combined appropriately by a data-reduction matrix calculation to yield the three forces and one moment acting on that chair. In turn these values from the left and right chairs are combined to determine the total loads on the fifth wheel.
The transducer system is nominally designed for use with trailers applying static fifth-wheel loads of up to 30,000 lbs. Calibrations show the system to provide better than 1-percent accuracy in Fx and Fy and about 2-percent accuracy in Fz and Mx. Other tests show that the load cells are quite insensitive to twisting and flexing of the frame rails to which they are mounted.
For further information about our fifth-wheel load transducer facility, please read this brochure.