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 Post subject: Precise effects of asym cores?
 Posted: Sun Aug 19, 2012 2:49 pm Post Number: #1 Post
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Can you help me find information on the exact effects on ball motion, of asym balls?

What I keep reading is the MB is used to "tune" the hook. Okay.

But what I'm looking for is just what it does during all stages of the ball's movement down the lane. It's been well established that the ball will eventually roll over its highest RG (the knob or whatever marked by the pin). We see that with the Determinator.

But just what do the irregularities in the asym core do to ball motion? Retard the precession? Enhance the precession? Act as a force that rotates the rotation axis to enhance ball motion?

Has Mo publilshed a paper that thoroughly explains this?


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 Post subject: Re: Precise effects of asym cores?
 Posted: Sun Aug 19, 2012 3:22 pm Post Number: #2 Post
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MrClutch wrote:
Can you help me find information on the exact effects on ball motion, of asym balls?

What I keep reading is the MB is used to "tune" the hook. Okay.

But what I'm looking for is just what it does during all stages of the ball's movement down the lane. It's been well established that the ball will eventually roll over its highest RG (the knob or whatever marked by the pin). We see that with the Determinator.

But just what do the irregularities in the asym core do to ball motion? Retard the precession? Enhance the precession? Act as a force that rotates the rotation axis to enhance ball motion?

Has Mo publilshed a paper that thoroughly explains this?

The line between the pin (low rg) and the M.B., is termed the pin to spin line. The farther the PAP is from that line, the later the transitions.
Moving the MB towards the VAL or away from it, changes the distance that the migrating PAP has to travel. longer=later transitions


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 Post subject: Re: Precise effects of asym cores?
 Posted: Sun Aug 19, 2012 6:04 pm Post Number: #3 Post
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MrClutch wrote:
It's been well established that the ball will eventually roll over its highest RG (the knob or whatever marked by the pin). We see that with the Determinator.





You have made two posts today which lead me to believe you are confusing a deTerminators role. A deTerminator adds energy to the bowling ball system which forces the ball to spin around the high RG axis which is also called the Preferred Spin Axis. While traveling down the lane, the spin axis of the ball will NOT migrate to the high RG axis because energy is not being added to the ball system.




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 Post subject: Re: Precise effects of asym cores?
 Posted: Sun Aug 19, 2012 7:50 pm Post Number: #4 Post
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I was going to include this discussion in my earlier post, but had to leave before I could find it:
viewtopic.php?t=3015


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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 1:21 pm Post Number: #5 Post
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Math,
You're right that energy input ends the instant the ball leaves the bowler's fingers. That's one reason why I've never liked calling the core a "motor." It's really a flywheel. But like the flywheel in a gyroscope, it's going to fight to find equilibrium.

If the lane were long enough and wide enough (think a gym floor), eventually the ball would roll over its pin (the high RG part of the ball).

We see that in the abbreviated time the ball spends on the bowling lane (no more than 3 seconds). The high RG (pin) fights for a stable position, and moves downward and forward (precession) as conservation of energy takes over.
It's why there's more flare with a pin in the strong position (something like 3 1/2") from the IT, than if the pin is already in the track.

Anyway, the question is... just what does the asymmetric nature of the core do in terms of high RG movement and axis migration?


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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 1:50 pm Post Number: #6 Post
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MrClutch wrote:
Math,
You're right that energy input ends the instant the ball leaves the bowler's fingers. That's one reason why I've never liked calling the core a "motor." It's really a flywheel. But like the flywheel in a gyroscope, it's going to fight to find equilibrium.

If the lane were long enough and wide enough (think a gym floor), eventually the ball would roll over its pin (the high RG part of the ball).

We see that in the abbreviated time the ball spends on the bowling lane (no more than 3 seconds). The high RG (pin) fights for a stable position, and moves downward and forward (precession) as conservation of energy takes over.
It's why there's more flare with a pin in the strong position (something like 3 1/2") from the IT, than if the pin is already in the track.

Anyway, the question is... just what does the asymmetric nature of the core do in terms of high RG movement and axis migration?


Gyro rotors don't 'fight tt find equilibrium' - they stay exactly in the orientation you put them in, which is kind of the point behind them...
The pin is the low rg axis, not high, and the PAP generally moves toward the grip centre (or at least towards the general area of the holes) - the pin simply doesn't move as you describe.
With respect your original question - strong asymmetric cores allow the driller to accurately place the axes of the ball relative to the PAP and be reasonably sure that the layout will survive drilling. :) They allow a wider range of reaction shapes and better predictability post drilling than symmetric cores.
Read the wiki - you will find the answers to your question in there in as much detail as you wish.

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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 2:54 pm Post Number: #7 Post
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MrClutch wrote:
Math,
You're right that energy input ends the instant the ball leaves the bowler's fingers. That's one reason why I've never liked calling the core a "motor." It's really a flywheel. But like the flywheel in a gyroscope, it's going to fight to find equilibrium.

If the lane were long enough and wide enough (think a gym floor), eventually the ball would roll over its pin (the high RG part of the ball).

We see that in the abbreviated time the ball spends on the bowling lane (no more than 3 seconds). The high RG (pin) fights for a stable position, and moves downward and forward (precession) as conservation of energy takes over.
It's why there's more flare with a pin in the strong position (something like 3 1/2") from the IT, than if the pin is already in the track.

Anyway, the question is... just what does the asymmetric nature of the core do in terms of high RG movement and axis migration?


All balls become asymmetrical after drilling.
I don't know what you mean by "high RG movement"?
Concerning axis migration, here is another good discussion (see #25 specifically THANKS STEVE):
viewtopic.php?f=13&t=69&start=20


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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 3:45 pm Post Number: #8 Post
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The pin is the predrilled Low RG Axis of the ball, not the High RG Axis. The "Mass Bias"/"Preferred Spin Axis" is the High RG Axis.

What actually precesses is the axis of rotation (the axis through the PAP). This axis precesses along the RG contour that it starts on in the real world. Given a long time, the gyroscope loses energy and must begin to precess along lower RG contours. Eventually, it would "seek" the lowest RG possible- i.e. the pin.

On a deTerminator, the added energy causes the axis of rotation to precess along higher RG contours until it reaches the High RG Axis- i.e. the MB/PSA.


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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 5:27 pm Post Number: #9 Post
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MrClutch wrote:
But what I'm looking for is just what it does during all stages of the ball's movement down the lane...

But just what do the irregularities in the asym core do to ball motion? Retard the precession? Enhance the precession? Act as a force that rotates the rotation axis to enhance ball motion?


Now, to get to the questions.

There's two properties when talking about the MB/PSA that are important to ball drilling:

1) Strength
2) Placement

(1) The strength is measured by the Differential Ratio of the ball after drilling. This is calculated by dividing the Intermediate Differential (a.k.a. Asymmetrical Diff.) by the Total Differential. For example, a 15 pound 716C by Track has a Total Diff. of .057" and an Intermediate Diff. of .016". The Diff. Ratio=.016/.057=.28.

The higher the Diff. Ratio (i.e. the more asymmetric the core), the quicker the ball reaction (sometimes this means sharper, always this means quicker forward roll). Also, the higher the Diff. Ratio, the stronger the gyroscopic properties of the ball. This means the ball will maintain tilt and rotation longer and thus skid further before beginning to hook.

(2) The placement of the PSA on the ball is actually not as important as the placement of the line between the pin and the PSA, the "pin-to-spin" line. The precession of the axis of rotation (PAP) increases when it crosses this line. Therefore, the closer the line is to the initial PAP, the sooner the ball will begin to hook. The further the line is from the initial PAP, the later the ball will begin to hook. This effect is stronger in more asymmetric balls. The distance between the initial PAP and the pin-to-spin line is measured by the Drilling Angle and can effectively vary between 10° and 90°.

Hope that helps.


Last edited by The Kid on Mon Aug 20, 2012 7:57 pm, edited 1 time in total.

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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 7:42 pm Post Number: #10 Post
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Again,
What I'm looking for is just what does it do, not whether it's stronger or causes a ball to maintain tilt longer.
Why does it maintain tilt longer? Is there a point in the ball motion that a strong asym core causes the precession to increase... or decrease? And why?

And... the pin marks the axis of low RG, but the highest mass of the core is below the pin. Sounds counter-intuitive, doesn't it?


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 Post subject: Re: Precise effects of asym cores?
 Posted: Mon Aug 20, 2012 8:14 pm Post Number: #11 Post
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MrClutch wrote:
Again,
What I'm looking for is just what does it do, not whether it's stronger or causes a ball to maintain tilt longer.
Why does it maintain tilt longer? Is there a point in the ball motion that a strong asym core causes the precession to increase... or decrease? And why?

And... the pin marks the axis of low RG, but the highest mass of the core is below the pin. Sounds counter-intuitive, doesn't it?


Stronger asymmetry maintains tilt longer because of the stronger gyroscopic properties. There is a greater resistance to change the axis of rotation. (http://forum.bowlingchat.net/viewtopic.php?f=13&t=4828)

Precession increases as the PAP migrates across the pin-to-spin line if the Diff. Ratio is greater than 0 (every postdrilled ball). Here's why:

The Kid wrote:
Based on the "why" behind the drilling angle: the higher the differential ratio, the stronger the effect of the drilling angle on the first transition.

This is because the drilling angle places the PAP "x degrees" from the minor axis of the RG contour. Objects in elliptical orbit (the PAP in this case) increase linear velocity once they cross the minor axis of the elliptical path, with maximum velocity at the major axis. So, the effect is that once the PAP migrates across the pin-to-PSA line (minor axis), the precession increases.

However, the shape of the RG contours are dependent on the differential ratio. A perfectly symmetrical ball has circular RG contours. As the differential ratio increases, the contours become more elliptical. The more elliptical the contours, the greater the increase in the precessional rate (also, circular orbits have no increase).

Thus, on symmetrical balls (very mild asymmetricals post-drilling) the precession hardly increases as the PAP crosses the pin-to-spin line (drilling angle matters less). Increasing the asymmetry would increase the effect (using a P3, P4, or balance hole 2" down the VAL from the midline). Or a larger change to the drilling angle needs to happen to noticeably affect the first transition (balance hole 2" down the VAL).


The Low RG Axis goes through the long dimension of any object with uniform density, I believe. Here's why:

The Kid wrote:
The axis through the length (longer dimension) of the core is the Low RG Axis.
The axis through the width (shorter dimension) of the core is the High RG Axis.

This is because the further the mass is away from the axis of rotation, the harder it is to rotate the object about that axis. With a football, the Low RG Axis is through the nose. The High RG Axes are the end-over-end axes.


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 Post subject: Re: Precise effects of asym cores?
 Posted: Thu Sep 13, 2012 5:17 pm Post Number: #12 Post
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MrClutch wrote:
Can you help me find information on the exact effects on ball motion, of asym balls?

What I keep reading is the MB is used to "tune" the hook. Okay.

But what I'm looking for is just what it does during all stages of the ball's movement down the lane. It's been well established that the ball will eventually roll over its highest RG (the knob or whatever marked by the pin). We see that with the Determinator.

But just what do the irregularities in the asym core do to ball motion? Retard the precession? Enhance the precession? Act as a force that rotates the rotation axis to enhance ball motion?

Has Mo publilshed a paper that thoroughly explains this?


All balls transition the same way, skid, HOOK, ROLL. ALL balls are asyms after drilling, but with different differential ratios. Stronger asyms (higher diff. ratios) transition through the hook phase faster, as long as everything else is equal. Read my BTM article on diff. ratio. It's in the Wiki.


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 Post subject: Re: Precise effects of asym cores?
 Posted: Thu Sep 13, 2012 11:40 pm Post Number: #13 Post
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Mo Pinel wrote:
All balls transition the same way, skid, roll, hook. ALL balls are asyms after drilling, but with different differential ratios. Stronger asyms (higher diff. ratios) transition through the hook phase faster, as long as everything else is equal. Read my BTM article on diff. ratio. It's in the Wiki.


Are not The Three Phases of Ball Motion Skid, Hook, Roll.

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 Post subject: Re: Precise effects of asym cores?
 Posted: Fri Sep 14, 2012 5:32 am Post Number: #14 Post
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bowl1820 wrote:
Mo Pinel wrote:
All balls transition the same way, skid, roll, hook. ALL balls are asyms after drilling, but with different differential ratios. Stronger asyms (higher diff. ratios) transition through the hook phase faster, as long as everything else is equal. Read my BTM article on diff. ratio. It's in the Wiki.


Are not The Three Phases of Ball Motion Skid, Hook, Roll.


You caught me. I screwed up!


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