A few days ago, I put up an image on Facebook of two different balls at different spots on the lane and asked people to guess the entry angle of each ball. This was done as a contest…the person with the closest guesses got a free one-year subscription to Bowling This Month. Here’s a large version of the image that was provided, for your reference.

Entry Angle Contest Image

This is the original image posted to Facebook.  The contest was to guess the entry angle of both the red ball and the blue ball.

We got some great guesses, actually.  I was surprised at how accurate some of you were, especially given how difficult it is to judge entry angle from the foul line, which was the vantage point of the image that was provided. I’ll give the correct values in just a minute for the entry angles of the two balls. But, instead of just leaving it at that, I thought it might be a good idea to give a bit of background information on what was different about these two ball paths, in case anyone was curious.

Drum roll please…

Without any further delay, here are the results:  the red ball’s entry angle is 3.31 degrees and the blue ball’s entry angle is 5.44 degrees.

The winning set of guesses was 3.26 degrees and 5.15 degrees.  That’s an average error of only 0.17 degrees.  Congrats to the winner, who either has a really good eye or really good luck!

Some explanation

In case you can’t tell, those aren’t real bowling balls in the image above. Additionally, the ball positions weren’t taken from actual shots that were thrown in real life. And, that isn’t even a real bowling center in the image. In fact, it’s all computer-generated. The ball paths originated from simulations performed using Powerhouse Blueprint and the image itself is a three-dimensional photo-realistic rendering of a “virtual” bowling center.  The ball path data from the Blueprint simulations was fed into the rendering software and the red and blue bowling balls were overlaid onto the lanes at the correct locations. That’s why we were able to report the entry angles to two decimal places…computers can do that easily, whereas people generally can’t.

So, obviously something was different between those two shots, right?  Yes, and actually, there are two differences between the red ball path and the blue ball path:

  • The ball’s location on the lane: the red shot was farther outside; the blue shot was more toward the middle of the lane.
  • The bowler’s axis rotation angle at the release: the red shot had an axis rotation angle of 40 degrees; the blue had 65 degrees of axis rotation angle.

First, let’s look at these two shots’ ball paths in Powerhouse Blueprint.

Ball paths from Powerhouse Blueprint simulations

These are the two ball paths in Powerhouse Blueprint. Here, we can also see where the two shots were relative to the oil pattern.

We’ll start by talking about the red shot. This type of ball path is fairly typical of what might happen to a bowler in the middle to later portions of a league or tournament session if the proper adjustments aren’t made as the oil breaks down. The ball catches so much of the dry in the midlane that it starts hooking far too early and, worse yet, it stops hooking far too early (at about 48 feet from the foul line, to be exact). This early hook and subsequent early roll are the reasons for the poor entry angle of just 3.31 degrees. This bowler might find himself in the pocket, but pin carry will probably suffer with such a low entry angle.

Now let’s talk about the blue shot. This is a good example of what kind of adjustment might be successful as the midlane dries out. This shot was thrown more into the heavier portion of the oil pattern. As a result, the ball encounters way less friction in the midlane, allowing it to retain more of its hooking power for the back end. Additionally, the higher axis rotation angle gives the ball a longer and stronger hook phase. In this case, the ball keeps hooking until just in front of the headpin. This allows it to enter the pocket at a much more respectable entry angle of 5.44 degrees, giving our bowler a much better chance of striking.

Finally, let’s return back to our virtual bowling center and we’ll take a look at these two shots from directly above.

Top View

Top view

From this angle (and with the correct 1:1 width-to-length aspect ratio of the lane), the two shots don’t really look that much different. They’re separated by just slightly more than one board at most. That’s part of the challenge with bowling…sometimes tiny differences, such as one board of hook on the back end, can cause drastic differences in how your ball goes through the pins.

This all seems very familiar…

There’s certainly nothing new here. If you spend some time watching the really good bowlers in your area, you’ll probably see this same exact adjustment combination made over and over again: as the oil dries up in the midlane, they’ll gradually move in and gradually increase their axis rotation angles. This type of knowledge and versatility is really one of the things that separates the extremely good bowlers from the rest.

And, BTM subscribers in particular will especially recognize this scenario, as Ron Clifton covered this in detail a few months back.

Anyway, I hope everyone enjoyed this contest and maybe even learned something in the process. Thanks to everyone who participated!

Bill Sempsrott

About Bill Sempsrott

Bill is the founder of BTM Digital Media, LLC and he manages the day-to-day operations of Bowling This Month. Bill has a graduate degree in Mechanical Engineering, he developed the Powerhouse Blueprint ball motion simulator, and he has been an avid bowler for more than 20 years.