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Sport Bowling

By Neil Stremmel

Entry Angle, Part 3

USBC research shows where your ball should be to achieve the best angle

The first two articles of this three-part series included a discussion of how United States Bowling Congress testing has shown that six degrees is the optimum angle of entry into the strike pocket. In the previous article, we discussed the equation of a line drawn from the pocket back toward the bowler at two, four and six degrees. Finally, we concluded that we must know how far a ball will push past the end of an oil pattern to determine how to get our ball on one of these lines into the pocket and how noting where the ball comes out of the oil can be crucial to telling us what entry angle we have.

Research completed on USBC Sport Bowlling patterns

During the past month, the USBC Specifications and Certification team (mainly research engineers Bob Roloff and Rory Holland and senior technician Jim Jaryszak) have been conducting research in the eight-lane testing facility in Greendale, Wisconsin to determine the average skid length, or "push", pas the end of the oil pattern to the breakpoint. I was confident that if we used a USBC Sport Bowling pattern in our research, the push would be contingent on speed and rev rate, but wondered which would be more dominant.

Since we didn't want the balls to see friction early - as can happen on a typical house shot - the test was performed on Sport Bowling lane conditions. We used two Sport patterns with the same amount of oil side to side but buffed out to distances of 37 and 41 feet. A group of 14 test bowlers with a wide range of ball speeds and rev rates provided the data by bowling on these patterns in our research center. Using the Computer Aided Tracking System (CATS), we could distinctly observe that shots rolled by our test bowlers pushed past the end of the pattern and further down the lane (in the oil) on the longer pattern, so I am confident we met our objective.

Data shows rev rate more important than ball speed

Let's start with a look at the data. In Figure 1, we see a summary of the results of this test.

Since I thought that speed would be the dominant factor in the amount of push past the oil line, the results were a little surprising to me. But once I thought about the fact that most higher average bowlers throw the ball from about 17 to a bit less than 19 miles per hour (a relatively tight range), it is clear that rev rate has a much larger variance among higher average bowlers (200-500 rpm).

Rev RateMPHPush (in feet)
170-200 16.9 2.3
200-250 17.7 2.7
250-300 18.1 5.4
300-350 18.0 7.7
350-400 18.4 6.3
400-500 18.7 5.9

Research data of test bowlers showing average speed and rev rate as associated with the "push" past the end of a USBC Sport Bowling oil pattern.

Figure 2

This graphic shows the ball path of a test bowler with a lower rev rate (about 180) and slower ball speed (17 mph). This bowler was playing a typical "down-and-in" line where the ball crosses the second arrow and has a breakpoint at about 40 feet.

Another potential discovery (that I'll think about during another sleepless night) is that a ball thrown with 350 rpm at about 18 miles per hour appears to be the optimum rev rate. Why? This preliminary research shows that at this rate a bowling ball seems to skid the proper amount to achieve optimum entry angle. As typical with research, more study is needed. Maybe this is why professional bowlers like Robert Smith and Michael Fagan felt like they needed to go to the Sarge Easter grip to cut down on their rev rate. Obviously, this will depend on conditions (lane surface, oil pattern, etc), but more often than not they seem to run out of room while trying to get the ball to push further down the lane.

Figure 3

The next task with this information is to add it to the equation I discussed in the February issue. Let's start by looking at the ball motion plots of two bowlers.

In Figure 2 we see a lower rev, slightly lower speed player trying to get the ball to the pocket. You can see the bowler is playing the typical down-and-in line, hitting the 10 or 11 board at the arrows with a breakpoint at about 40 feet on a 37-foot pattern.

Figure 3 shows that a bowler with a very high rev rate and fairly high speed playing about 13 (further right on a shorter pattern - smart!) with a breakpoint of 43 feet on the same 37-foot pattern.

Sport Bowling tip of the month
Bob Learn Jr.

On the PBA Tour, creating strong entry angle is based on how much axis rotation a player can achieve. This is for two reasons. First, onthe PBA Tour, we play the end of the pattern where league players create entry angle by taking advantage of friction to the right. High rev rates are needed on Tour so the ball can slow down soon enough to create the optimum entry angle. Secondly, the PBA exempt player' high rev rates create a laydown area much farther inside. Tommy Jones, Wes Malott and a few others can take advantage of playing further left because of their extremely high rev rates and axis rotation. Of course, the best players on Tour can adjust their speed, rev rate and axis rotation. Champions are crowned each week based not on who hits the pocket the most, but who can create the best entry angle.

How does this relate to amateur players? When you can throw your most comfortable speed and play the friction to the right, you are usually able to create a strong entry angle. But if you encounter a condition that dictates moving deeper on the lane, keep in mind that you may have to increase your axis rotation and/or decrease your ball speed to maintain or create optimal entry angle. Visit bowl.com to seek a USBC certified coach in your area who can help you improve those skills and make you a more versatile player.

Editor's Note: Bob Learn Jr. is the Proprietor Relations Specialist for the United States Bowling Congress in Greendale, Wisconsin. The USBC certified coach has more than 20 years of experience on the Professional Bowlers Association Tour, where he owns five career titles including the 1999 U.S. Open.

Pattern Length / Entry Angle
45 14.1 14.4 14.7
44 12.8 13.4 13.9
43 11.6 12.3 13.0
42 10.3 11.3 12.2
41 9.0 10.2 11.4
40 7.8 9.2 10.5
39 6.5 8.1 9.7
38 5.2 7.1 8.8
37 4.0 6.0 8.0
36 2.7 5.0 7.2
35 1.5 3.9 6.3

This chart shows the board at which your ball should come out of the oil to obtain the referenced entry angle. It is based on ball speed of 18.0 mph and a rev rate of 350 rpm, but also is valid for 19.0 mph, 500 rpm and 17.0 mph, 200 rpm.

Note that in the above figures the high rev, higher speed player sent the ball to about the fifth board at 50 feet on the six-degree entry angle line per my chart published in February. This bowler did achieve six degrees. Also note that the lower rev, slower speed player had the ball at about the ninth board at 50 feet on the four-degree entry angle line per my chart. I love it when the real world data backs up the equations derived in the lab!

Charting your course to the pocket

Using the above information and the table from February, I have created the chart shown in Figure 4. This diagram is based on speed and rev rate and shows you where you want the ball to come out of the oil (you'll need to know the pattern length) to achieve a four-, five- or six-degree entry angle.

Be advised that the accuracy of the chart's numbers is highly dependent on the friction on the outer portion of the lane. If you are bowling on a typical house shot, your breakpoint will depend on how quickly you get the ball outside, but on most types of challenging conditions such as Sport, USBC Open, Masters, Queens and most PBA patterns, this will help you learn to achieve the best entry angle.

It will be especially helpful on fresh oil when you are trying to get lined up for maximum area and best carry. Also realize that, based on the pattern, this point/board may not give you the most area or margin for error, just the best entry angle into the pocket. Since most patterns are between 35 and 45 feet long, I have only included this information in the chart. One observation is that the chart shows how challenging it is to achieve a six-degree entry on a short pattern because the ball must be so far outside.

This concludes the three-part series on entry angle. I hope this helps you determine what entry angle you are obtaining, as well as how to get there. Now maybe I can finally get some sleep.

Neil Stremmel

Neil Stremmel is the Technical Director for the USBC in Greedale, Wisconsin. He is a Mechanical Engineer (BSME from Bradley University in Peoria, illinois), an IBPSIA certified technician and a Master Computer Aided Tracking System instructor. Neil previously worked in the nuclear power and aerospace industries. He has served as a local ABC director and is a lifetime bowler who began working in a center at age 13.