Determination of Optimal Handle Sizes by use of Normalized Hand Sizes in a Pulling Task

Abstract

Two handle shapes (double frustum and oval) with different sizes, resulting in a total of 10 handles were tested to determine optimal handle sizes in a pulling task. Force data were collected by force sensitive resistors (FSR), which were placed on the palmar surface of the fingers. Subjective ratings of discomfort were also recorded for each handle. The results of subjective ratings showed that medium sized-handles were described as being more comfortable than the other sizes, and double frustum handles required less finger forces than oval handles. ‘Normalized Hand Size (NHS)’, which is the ratio of handle circumference to user's hand length was applied to predict the optimum handle size for the subjective ratings as well as finger forces in a pulling task according to the user's hand size. in oval handles, generally medium handles showed higher preference and required less finger forces than large handles. in case of the double frustum handles, the 60.9% NHS was the best ratio for the least subjective discomfort ratings and the 58.1% NHS was recommendable for the least finger force requiring in a pulling task. Based on the results of NHS study, 34.4∼38.1 mm and 31.4∼35.0 mm were recommended for middle hand size groups of male and female, respectively. The optimum handle sizes for the males were about 8.1∼8.7% larger than that of the female.