Gear Fault Detection using Transmission Variance Measurements

This paper reports the findings of a study that used measurements of shaft rotational position, made using inexpensive Hall effect sensors and magnets mounted at the ends of a gearbox input and output shafts, to determine gear "transmission variance". The transmission variance as a function of gear/shaft rotational position, were then used to detect gear faults and fault severity. The results show that variations in the rotational position of the output shaft relative to that of the input shaft (the transmission variance) can be used to reveal gear mesh characteristics, including faults such as cracked or missing gear teeth and flattened gear tooth faces, in both plastic gears and steel gears under realistic loads and speeds. The method described has potential advantages over traditional analysis methods based on gearbox vibration and/or oil analysis.