Axistiltguide.xls (file size: 848 KB, MIME type: application/vnd.ms-excel)
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The AxisTiltGuide.XLS provides means of calculating an "effective rev rate" based on bowler's axis tilt. The idea was to allow for a more accurate determination of sweet spot angle sums. However it is a bit too elaborate for the average tilts between 0* and 30*. The already known rules of thumb work quite well in that range.
As a side effect the spread sheet can also be used to find axis tilt based on either measuring the length of the track or the arc across the track.
The theory behind the spread sheet:
The same ball is thrown with equal speed, axis rotation and rev rate but varying axis tilts.
The maximum frictional force that can be transferred at the contact between ball and lane is determined by the friction coefficient (dictated by coverstock and lane material) and the force pressing the ball onto the lane surface (ball weight):
Friction Force = Friction Coefficient x Weight Force
The friction coefficient varies over the lane depending on the oil volume. This is independent of axis tilt. Thus all shots with this ball have the same friction potential available to them.
From it is conluded that lower tilt bowlers just make more use of the available friction than higher tilt bowlers due to the different track lengths. The track length can easily be calulated from the tilt:
Track Length = Pi x Ball Dia. x cos(Tilt)
With each rotation this length of surface rubs over the lane surface. The speed of the ball surface rubbing on the lane is actually what creates the frictional force that moves the ball to the left:
Track Speed = Track Length x Rev Rate / 60
Lower tilts have higher surface speeds. This can be seen as a higher effective rev rate. Vice versa higher tilts have lower effective rev rates. Only that the effect of higher tilts is more extreme due to the non-linear nature of this effect. 600revs are no good if axis tilt is 80*...
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|current||05:43, 5 October 2010||(848 KB)||Megamav|
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