A portable instrument of the seismograph type has been designed for measuring the riding-quality of vehicles. Headings are made by a continuously revolving counter that automatically sums up the vertical displacements of a partly suspended weight. As the counter readings are a measure of the riding-quality, a large reading indicates poor riding and, conversely, a small reading indicates good riding. An arbitrary scale graduated into revolutions of the counter per mile of travel translates the readings into riding-quality; a reading of 10 indicates “very smooth,” 20, “good,” etc. The instruments have been calibrated in a special testing-machine in which the readings can be observed under an harmonic motion of fixed period and amplitude.
Comparison of the riding-qualities of balloon tires and of cord tires, made on three different automobiles run over a variety of roads, shows results that are very favorable to balloon tires. Data on the effect of shock-absorbers and of car-speed on riding-quality are now being obtained. Detailed records of the riding-quality of an airplane, as measured by the integrating instrument, show the airplane to be slightly better than the best automobile.