Experimental stress analysis has proved itself to be a useful and valuable engineering tool that was used with design and testing programs on experimental snowmobiles to assure reliability. It also helped reduce the testing time. Design changes were made with an accurate knowledge of the stresses involved and in some cases were processed before endurance testing produced a broken part. V-belt sheaves were analyzed and strengthened. A high-temperature evaluation of piston material helped cure a piston pin hammering problem.