Pitcher Protection Device

Design Specifications

 

In order to protect the pitcher’s head and neck from a line drive ball, the protection device must satisfy the following specifications:

• It must respond to a signal from the tracking system.

• It must deploy fast enough to protect the pitcher before the ball arrives. The fastest speeds a batted ball reaches are typically seen on home run hits, and can reach up to 120 mph (53.6 m/s).5 At that speed, a ball would reach the mound (18.4 m / 60.5 ft. away) in 0.35 seconds. Thus, the system should deploy in under 0.05 seconds (giving the tracking system a minimum of 0.3 seconds to determine if the pitcher will be hit). These are conservative estimates, as a typical line drive is not travelling as fast as a home run.

• It must withstand the force of impact of a line drive ball. An investigation of baseball eye injuries used load cells in an artificial orbit (eye socket) to determine the impact force of a baseball at various ball speeds. The study found a strong linear relationship between impact force and baseball velocity and a regression analysis (R2 = 0.98) yielded the following relationship: Impact force (N) = 76.6 x Ball Speed (mph) – 5716. From this equation, with a ball speed of 120 mph (53.6 m/s), it was determined that the protection device must withstand a force of 8,550 N.

• It must absorb sufficient impact energy to prevent pitcher injury. A common baseball impact injury is a zygoma (cheekbone) fracture. A study combined the relationship between ball speed and impact force with zygoma strength data to determine the risk of fracture at various ball speeds. The study predicted a probability of fracture of less than 10% for balls traveling 15 mph (6.7 m/s) or slower7.  Another study examined the response of the maxilla (upper jaw bones, another common facial fracture) to blunt impact of various forces. As with the zygoma study, the risk of fracture was determined for each force, with a 10% fracture probability corresponding to a 670 N impact8. Based on the force-velocity relationship previously described, this force corresponds to a ball speed of roughly 16 mph (7.2 m/s). The results of these two studies indicate that an impact velocity of 15 mph (6.7 m/s) is sufficiently slow to avoid significant injury risk. Thus, based on the kinetic energy change for a 145 g baseball decelerating from 120 mph (53.6 m/s) to 15 mph (6.7 m/s), the protection system must absorb at least 205 J of impact energy.

• It must not pose an injury risk to the pitcher before, during, or after deployment.

• It must contain a power supply sufficient to receive a signal from the tracking system and then deploy the device.

• It must cost no more than $50,000 per device. As this device is intended for use in MLB games, the maximum cost can be very high – the league is very successful and has the money to pay for player safety equipment. The cost estimate was determined using the pitcher’s salary to represent his monetary value to the team. For the 2014 season, the minimum MLB salary is $500,000.9 For a pitcher who plays every fifth game of a 162 game season, this salary translates to about $15,000 per game. Thus, if a minimum salary player were to miss just a single game, it would represent a value loss of $15,000. If the average league salary, $3.4 million is used, this lost value jumps to over $100,000.9

Different embodiments of this design are possible. We envision two types of possible solutions: a device worn on the pitcher’s body and a device on the ground between the pitcher and the batter. These embodiments each have specific design requirements.

A device on the pitcher’s body must meet the following design specifications:

• It must be lightweight. The current MLB-approved protective headgear, the isoBlox cap, adds approximately 200-250 g to the weight of the cap (85-115 g). This solution has been rejected by players as too heavy, thus our device must weigh less. A survey of Washington University in St. Louis pitchers indicated that pitchers would accept a moderate increase in cap weight, and following discussions with those pitchers, it was determined that the device must weigh no more than 150 g.

• It must be aesthetically pleasing so that pitchers will be willing to wear it. This specification presents issues as aesthetics are inherently objective. However, in an attempt to gain insight into how baseball players view the aesthetics of possible design solutions, Washington University in St. Louis pitchers were surveyed for their opinions on protective devices.

• When deployed, it must be large enough to protect the pitcher’s entire head and neck: a minimum protection area of 25 cm x 30 cm (dimensions based on average male head size).

A device on the ground must meet the following design specifications:

• It must not interfere with players moving around or over it. Bunted balls, for example, are often hit in the area between the pitcher and home plate – these type of plays must not be affected.

• It must protect pitchers of all heights, providing protection to at least 2.13 m (7 ft.) from the ground, as the tallest pitchers in the MLB can be 2.1 m (6 ft. 10 in.). The pitcher’s mound is 25 cm (10 in.) high, but the pitcher’s step forward off of the mound in their pitching motion, as well as typically bending at the waist, so this height was not added. The protection area width must be 1.3 m, based on a typical pitching motion.