The United States Bowling Congress Equipment and Specifications team continues to study pinfall with string machines, and has identified several factors affecting pinfall.
Based on testing, the following settings reduced the number of split conversions and rebounding of pins to an acceptable limit:
1. The string length has a minimum limit of 65 inches, measured from the ball cup to the point the string enters the pin.
2. Placing the pin curtain between 12 and 16 inches from the end of the lane, measured from the back of the tail plank.
3. Placing the ball stop cushion a minimum of 33 inches from the end of the lane, measured from the back of the tail plank.
4. Assuring the kickback walls on both sides of the lane have a minimum thickness of 2 3/4 inches.
The preliminary specifications do not take into account variables that have not been submitted for testing to date, including the effects of different construction material or design elements.
USBC said it is encouraging manufacturers to design string pinsetters that meet the preliminary specifications to submit for additional testing, with USBC evaluating the data with a goal of establishing final specifications.
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