EN
The friction testing rig was improved by applying a microcomputer as part of the installation. Values of external coefficients of triction against underlayment were studied in the case of soiled and clean tubers of one variety of potatoes as well as clods and stones picked from potato fields. Rubber and steel underlayments were used. The existance of statistically valid differences between friction coefficients was confirmed, particularly regarding the steel underlayment. Some of these differences may have an importance in the process of mechanical crop separation.