USBC proposes preliminary specifications for string pinsetters

Learn more about USBC's research on string pinsetters.

- The United States Bowling Congress is sharing additional data and proposing preliminary specifications to the manufacturers of string pinsetters.

The USBC Equipment and Specifications team has been taking part in a comprehensive research study on string pinsetters, looking at the scoring and pinfall variables between string pinsetters and free-fall machines.

USBC is investigating the possibility of certifying string pinsetters and string pin bowling as an independent category of equipment and competition, separate from free-fall machines and standard American Tenpins bowling.

String pinsetters currently are non-approved equipment and may not be used in USBC-certified competition, including USBC-certified leagues and tournaments.

After the most recent report in September 2021, the USBC Equipment and Specifications team identified several factors affecting pinfall. These factors included the string length, pin curtain, ball stop cushion and kickback thickness.

Adjustments were made to the string length, pin curtain location and ball stop cushion until results approached those of free-fall machines, and a design of experiment was conducted to identify the best combination of these properties to reduce the rate of splits being converted due to interference from the strings.

Based on testing, the following settings reduced the number of split conversions and rebounding of pins to an acceptable limit:

  • The string length has a minimum limit of 65 inches, measured from the ball cup to the point the string enters the pin.
  • Placing the pin curtain between 12 to 16 inches from the end of the lane, measured from the back of the tail plank.
  • Placing the ball stop cushion a minimum of 33 inches from the end of the lane, measured from the back of the tail plank.
  • 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 related to string pinsetters.

USBC 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.