### The Blueprint Blog - The Latest in Blueprint News, Tutorials, and Technical Info

#### Blueprint's Bowler Delivery Parameters: An Introduction

Date Posted: November 20, 2011

Category: Blueprint Tutorials

One of the features of Powerhouse Blueprint is its ability to simulate a bowling ball's on-lane performance using a bowler's actual delivery parameters.  Delivery parameters include everything necessary to describe how the ball is rolled.  This post will provide some definition for these parameters so you can be sure you are correctly interpreting the values you use in Blueprint.

##### Target Line Parameters Since the target line inputs are pretty self-explanatory, we'll lump them together and describe them all at once, rather than separately.  In short, the three target line inputs tell Blueprint where the ball is at the foul line and what its "launch angle" is, based on target ball position and target distance from the foul line.  In the example shown, this ball is placed on the 20th board at the foul line and it is "aimed" at the 15th board at a distance from the foul like of 14 feet (which is approximately how far the third arrow is from the foul line).  On-lane, this looks like the following: Pretty self-explanatory?  We hope so.  If not, then just experiment with this in Blueprint for a few minutes and you should pretty much get the hang of it.

##### Ball Speed

Blueprint requires that you input a bowler's ball speed (in miles per hour, or mph) at the release.  This is the speed of the ball as it leaves the bowler's hand.  This is quite different than average ball speed (as the ball travels the entire length of the lane) and extremely different than the ball speed reported by down-lane automatic score keeping systems.  Why?  Because, in general, the ball loses a fairly significant amount of its launch speed as it encounters friction during its trip down the lane.  For example, consider the speed of the ball in the above target line example: The launch ball speed in this example is 17 mph.  By the end of the lane, this ball is traveling less than 14 mph.  At 50 feet from the foul line (which is in the vicinity of many automatic score keeping system's ball speed sensors), the ball is traveling about 15 mph.  The reason this distinction is important is because using incorrect (non-launch) ball speeds in Blueprint will result in a lot of error in predicted ball paths.  Continuing this example, if you were to input 15 mph as the ball speed instead of the correct value of 17 mph, Blueprint would predict the ball path shown below in red: What does this show?  It shows that if you were to make this input error, Blueprint would predict that the ball would hook DRASTICALLY more (about six boards, in this case) than it would in reality.  So, to summarize, make sure you are using launch ball speeds in Blueprint to ensure that your ball path predictions are as accurate as possible.

##### Rev Rate

Similarly, Blueprint utilizes a bowler's rev rate (in revolutions per minute, or RPM) at the release.  Just as was the case with ball speed, the release rev rate is significantly different than the average rev rate (as the ball travels the entire length of the lane).  This is because, in general, the rev rate significantly increases as the ball encounters friction down-lane.  Again continuing the above example, take a look at this ball's rev rate as it travels down the lane: By the time this ball gets to the end of the lane, its rev rate has increased from 350 RPM to over 550 RPM.  If you were to attempt to utilize an average rev rate (say, 425 RPM in this example) in Blueprint, combined with an automatic score keeper ball speed of 15 mph, you would end up with a predicted ball path as shown below by the green line: As shown, the combined error of using a down-lane ball speed and an average rev rate as inputs results in a very large over-hook prediction by Blueprint (10 boards in this example).  So, again, as was the case above with ball speed, make sure that you utilize launch rev rates in Blueprint to ensure that the ball path simulation is as accurate as possible.

##### Axis Rotation Angle

Axis rotation angle is a measure of the amount of side roll the ball has relative to its direction of travel.  Again, Blueprint expects that you will input the axis rotation angle at the ball's release point.  A ball with very little side roll has a low axis rotation angle (for example, 0 to 20 degrees) and a ball with a lot of side roll has a high axis rotation angle (60-90 degrees).

The best way of determining a bowler's launch axis rotation angle is by observing the location of the ball's rotation axis at the release (commonly called the "positive axis point," or PAP).  If, when viewed straight from behind, the rotation axis is in the center of the ball, this would correspond to an axis rotation angle of 90 degrees.  If, however, the rotation axis is all the way on the left edge of the ball (when viewed from behind, for a right-handed bowler), this would correspond to an axis rotation angle of 0 degrees.

While the above is certainly a vague description, it hopefully at least provides a starting point for those readers unfamiliar with axis rotation angle.  We will try to expand upon this topic in a future article and provide more details on exactly how the axis rotation angle can be calculated using video analysis.

##### Axis Tilt Angle

Axis tilt angle is a measure of the amount that the ball's axis of rotation is tilted from the horizontal direction.  0 degrees of axis tilt means that the ball's axis of rotation is purely horizontal (parallel to the surface of the lane).  90 degrees of axis tilt means that the ball is spinning like a top (and hence, rotating about a purely vertical axis).  Axis tilt can be measured using video analysis (by looking at the inclination of the axis of rotation relative to the horizontal direction), but a better method is to measure the diameter of the ball track, which is directly correlated to axis tilt angle.

Again, we hope to provide a more detailed description of axis tilt angle in a future article, along with the procedure for calculating tilt from ball track diameter.

##### Loft Distance

Finally, we arrive at loft distance, which is perhaps the simplest input parameter in Blueprint.  Loft distance, quite simply, is the distance (measured in feet) from the foul line that the ball lands on the lane.  There's really nothing more to say about this, so we'll just leave it at that!

##### But How Do I Measure All Of These Things?

Obviously, the big weakness of this article is that it doesn't provide much, if any, guidance on how to best measure these bowler input parameters.  While we plan to tackle this topic in a future article, we would for now like to recommend that you visit the BowlingChat.net "Bowler Measurements" Wiki, which provides some great information on obtaining accurate bowler delivery parameters.