Spin Time

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Spin time... what is spin time?

Spin time is a measurement using a DeTermintator to determine how fast a ball design will transition from hook to roll. this is the hook zone.
This measurement is closely related to differential ratio, and the amount of asymmetry a ball has.
So balls with high intermediate differentials and differential ratios have lower spin times than more symmetrical balls.

Design means, it could be a drilled design or an undrilled design.
Spin time is not a real world measure, only a value to relate to.
Balls do not take 4 to 10 seconds to transition, they would run out of lane!

Undrilled true symmetrics have an infinite spin time. This is due to an absense of a High RG axis.
Once a ball is drilled, it has a PSA due to an imbalance in the ball from the holes altering the design.

Any ball with an intermediate differential, drilled or undrilled will have a PSA.

The lower the spin time the faster the ball will respond to friction and transition to the roll phase.
Spin time is important because we can determine, without throwing the ball down the lane, approximately what the hook shape will look like.

Here are some examples of drilled ball spin times, in relation to their hook shapes.
Its important to note that the bowler will also determine hook shape based on their release specifications.
The below examples are related to a median bowler, average tilt, average rotation, matched Speed/Rev Rate relationship.

Sharp Breakpoint: Less than 5.5 Seconds, has a very short hook phase. The roll phase line moves down on the diagram.
Benchmark: Between 6 and and 8 Seconds. The roll phase line moves not much on the diagram.
Control: Greater than 9 seconds, usually up to 12. The roll phase line moves up on the diagram.

Its important to note the skid phase is not affected much if at all, only the roll phase line, also known as the "2nd Transition".

Undrilled balls also have spin times, as long as they are not true symmetrics.
You can refer to the intermediate differential values below as a guide as to the amount of asymmetry in a ball.

.000 is a True symmetric, no PSA.
.000 to .007 is treated as a symmetric because the PSA will migrate toward (not necessarily in) the largest hole in the ball, which is usually the thumb hole.
.008 to .012 is a mild asymmetric.
.013 to .017 is a medium strength asymmetric.
.018 to .022 is a strong asymmetric.
.023 and above is a very strong asymmetric.


Now that we've established what spin time is, how can we affect spin time?

Multiple adjustments can be made for spin time, including Pin to PAP distance, VAL angle and where balance holes are placed.

Large VAL angles reduce flare, and increase spin times.
Pin to PAP distances of less than 4" on symmetrics and greater 4" on asymmetrics reduce spin times and induce roll faster.
Balance holes of P4 and P3 will reduce spin times, and the deeper the holes are, the more the spin time is reduced.
P2 balance holes do not have much affect on spin time they are very much between making a ball's core taller and fatter, inbetween symmetric and asymmetric.
P1 balance holes increase spin time by making the ball more symmetric.

Remember: the deeper the hole, the more you will influence the ball reaction, either increasing or decreasing spin time.