Dynaflect comprises a dynamic force generator, together with a set of motion sensing devices, mounted on a small trailer, and a motion measuring system which is normally carried in the towing vehicle. Deflections are measured while the trailer is halted for a brief time at the desired location. The motion sensing devices are lowered into contact with the surface and the results are read by the operator In the towing vehicle.

The force generator produces a vertical force which varies sinusoidally at the rate of 8 cycles per second. The total force applied to the material beneath the trailer consists of the static weight of the apparatus, 2000 pounds, plus the dynamic force which alternately adds to and subtracts from this weight. The peak to peak excursion of the dynamic force is 1000 lbs. This force Is applied to the ground through a pair of rigid wheels.

The material on which the steel wheels rest deflects downward and upward In synchronism with the 1000 lb. repetitive force. The amplitude of this Induced motion is sensed by means of geophones which are lowered Into contact with the surface at various distances, along the trailer tow bar, from the point of application of the force.

Since the motion is cyclic, the determination of its amplitude requires no fixed reference point in the vicinity. Accordingly, the Dynaflect system is immune from certain errors which affect all deflection measuring methods which require, a local reference point. The Dynaflect system employs an inertial reference, which may be regarded as located at the center of gravity of the earth.

The deflection measurements are read on a digital display In the control unit, which Is normally located beside the operator on the front seat of the towing vehicle. The control unit also provides for complete remote operation of the system. The operator need not leave the front seat, of the vehicle, except during the initial daily calibration procedure.

Provision is made for measuring deflection at  as many as five different distances form the load application point, ranging from 4 inches to several feet ( limited only by the length of the connecting cables to the individual geophones). This permits the shape of the "deflection basin" to be determined. For many applications, however, it suffices to measure only the deflection close to the load point. A remote controlled lift mechanism in the trailer moves the force generator, with its force wheels, in or out of contact with the ground. When out of contact, the trailer is supported on its tires travel at normal vehicle speeds. With the force wheels down, tires lifted, the trailer may be moved short distances, from one measuring point to another, at speeds up to six miles per hour. The sensors are raised and lowered by remote control to enable such moves to be made quickly.

Total power for Dynaflect Is obtained from the 12 volt electrical system of the towing vehicle. A set of cables Is furnished to supply current for the operating functions as well as for the required stop, tail and turn signal lights on the trailer.