Author Topic: Does CG maddah when finding unmarked MB? (Read 2949 times)

JessN16 · « **on:** April 06, 2008, 02:59:06 PM »

Just popped into my head today...

Let's say I have a ball with an unmarked MB. The quick-n-dirty way to find the MB, for the 99% of us without access to a Determinator, is to draw a line from pin through CG out to 6 3/4 inches and mark the MB there.

If this is true, kicking out the CG or keeping it in grip center gives you two different hook shapes, as you could end up moving your MB all the way from thumb-positive quadrant near the VAL to thumb-negative quadrant, in the track, just by swinging the CG about 2 inches laterally relative to the pin.

True or false?

Jess

Moon57 · « **Reply #1 on:** April 07, 2008, 06:17:48 AM »

From what I've gathered on here, unmarked mb's have very little effect on ball reaction.
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Moon
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So many questions, so little time but I'm having fun.

purduepaul · « **Reply #2 on:** April 07, 2008, 06:25:08 AM »

Jess-

If the ball does not have a marked mass bias it is symmetrical. If it is symmetrical, you can draw a 6 3/4" line through the CG or through 3" away from the CG, the high RG equator will always be 6 3/4" away from the pin regardless of CG position.

spinner031 · « **Reply #3 on:** April 07, 2008, 06:28:24 AM »

I've thought of this too.

Jess means that when you move the MB, you also move the CG. So if you move the CG back a few inches, the MB follows, and you'll get a different hook shape. Try to picture that.
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shelley · « **Reply #4 on:** April 07, 2008, 09:09:16 AM »

The other theory is that by moving the MB (and hence the CG), you are affecting the need for a weight hole and possibly where the weight hole needs to be. And the weight hole affects the ball reaction, not the "MB".

If the MB isn't marked, ignore it.

SH

dizzyfugu · « **Reply #5 on:** April 07, 2008, 10:04:30 AM »

I would not talk about "mass bias" here. The mass bias forces the ball/core into its stable end roll position through the core design and its dynamic properties. A symmatrical core, or better : one with a low MB, does the same, it just takes much more time. I'd therefore rather think of the PSA, the preferred spin axis. In a low MB ball, you will find it with the 6.75" line from the pin through the CG, since the CG is the only force that creates the core's static weights and determines its PSA. With a strong MB, the core design overrides the CG's effect, and that's why it becomes pretty irrelevant when drilling a strong MB piece (while the CG still gives some indication about the internal weigh distribution, e. g. for a balance hole to make the ball legal again).

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Strapper_Squared · « **Reply #6 on:** April 07, 2008, 11:05:58 AM »

Possibly prior to drilling. After drilling, the PSA is going to be approximately where the thumb is located (where the core has been reshaped)... regardless of whether the cg is left, middle, or right of the grip line. Determinator will confirm this. A weight hole can influence the ending position of the PSA (basically shifting it somewhere between the thumb hole and the weight hole (depending on the size/depth of the weight hole). The only influence the cg has is determining where (and how large) the weight hole is located to make the ball legal.

S^2
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JessN16 · « **Reply #7 on:** April 07, 2008, 01:38:00 PM »

quote:
Possibly prior to drilling. After drilling, the PSA is going to be approximately where the thumb is located (where the core has been reshaped)... regardless of whether the cg is left, middle, or right of the grip line. Determinator will confirm this. A weight hole can influence the ending position of the PSA (basically shifting it somewhere between the thumb hole and the weight hole (depending on the size/depth of the weight hole). The only influence the cg has is determining where (and how large) the weight hole is located to make the ball legal.

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The only thing about your response I would question is this: "After drilling, the PSA is going to be approximately where the thumb is located."

If that's the case, what's the difference between putting a marked MB in the track, or on the VAL? If the MB is going to shift to the thumb after drilling anyway, that would suggest pre-drill MB placement isn't relevant, and I don't believe that to be the case.

Jess

purduepaul · « **Reply #8 on:** April 07, 2008, 03:27:49 PM »

The PSA on a drilled symmetrical ball will be approximetly where the thumb is correct.

The PSA on an assymetrical defined as a ball having an intermediate of higher than 0.010" will approx be in the same spot. However certain higher assymetricals with pin down drillings may shift the low rg axis.

Paul

JessN16 · « **Reply #9 on:** April 07, 2008, 03:58:13 PM »

quote:
The PSA on a drilled symmetrical ball will be approximetly where the thumb is correct.

The PSA on an assymetrical defined as a ball having an intermediate of higher than 0.010" will approx be in the same spot. However certain higher assymetricals with pin down drillings may shift the low rg axis.

Paul

So if you have a very strong MB ball that is pin over bridge and the MB way away from the thumb (say, 3 inches away and past the VAL), the PSA is still going to be the thumb hole?

No disrespect but I find that exceptionally difficult to believe, for a couple of reasons: One, just because I don't think there would be such an emphasis put on sym-vs-assym stuff in the industry if it was all a bunch of hooey. Secondly, I own several strong assym pieces, most with pin-up drillings, and there is a clear difference from my sym stuff as to how it rolls and where it tracks.

We keep finding out that certain things don't matter (thumb weight, CG placement, top weight, now MB placement), yet how do we account for differences in performance that are clearly visible (i.e., where a ball tracks, hook shape, etc.)?

I suppose I could be to blame; I could be throwing certain pieces differently than I do others. But if that's the case, there's a dichotomy: I'm not good enough to be consistent from one different ball to another, but I'm consistent enough to throw one ball the same way every time and a different ball a different (but same) way all the time.

Also, on a separate subject, if the reason the thumb hole is the default PSA, what happens if you drill a thumb hole shallow (i.e., doesn't hit the core) and the finger holes deep? I also drill three finger holes in every ball (pinky hole), meaning I remove more finger weight than most bowlers. That would certainly affect me, right?

Jess

laufaye · « **Reply #10 on:** April 08, 2008, 01:59:32 AM »

Jess,

Please read purduepaul's post one more time.

And let me try to explain it.

Symmetrical core shaped ball is not going to have a marked MB on the ball.

Asymmetrical shaped core may or may not have a marked MB, its all up to the manufacturer.

Asymmtrical shaped core can spin symmetrically, meaning the int diff/MB diff can be close to zero.

Asymmetrical shaped core with a marked MB can have very low int diff/MB diff, as Paul stated less than 0.010, in this case the MB position after drilled is not going to hold its spot, it might not went all the way to the thumb hole area but definitely going to shift, such as the Temper. Higher Int diff/MB diff ball will hold its spot, at the moment the highest pre-drill ball is the LevRg. However, after drill can increase the int diff/MB diff as well.

Asymmetrical shaped core WITHOUT marked MB does not mean it has no int diff/MB diff, can be high can be low, just that the manufacture didn't mark the ball and didn't state the diff.

So when you drill a symmetrical shaped core and spin symmetrically ball and use the pin through CG 6 3/4 to mark a MB to layout a ball, most of the time is a bit meaningless, coz without a weight hole the ending MB will still get close to the thumb hole. Now with a weight hole, when is deep enough, as S^2 stated the ending MB will be in between the thumb hole and the weight hole depends on the size and depth difference of the 2 holes, but still be 6 3/4 away from the pin.

To go in a bit more detail on those numbers, asumming you know what is RG, RG diff is the difference betwen the high RG and the low RG, meaning the RG values betwen the X axis(the axis along the pin) and the Y axis. The Int diff/MB diff is the difference between the Y axis and the Z axis.

I am sure if you have more question you can call Paul and he can explain to you more.
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Laufaye

JessN16 · « **Reply #11 on:** April 08, 2008, 02:10:23 AM »

quote:
Jess,

Please read purduepaul's post one more time.

And let me try to explain it.

Symmetrical core shaped ball is not going to have a marked MB on the ball.

Asymmetrical shaped core may or may not have a marked MB, its all up to the manufacturer.

Asymmtrical shaped core can spin symmetrically, meaning the int diff/MB diff can be close to zero.

Asymmetrical shaped core with a marked MB can have very low int diff/MB diff, as Paul stated less than 0.010, in this case the MB position after drilled is not going to hold its spot, it might not went all the way to the thumb hole area but definitely going to shift, such as the Temper. Higher Int diff/MB diff ball will hold its spot, at the moment the highest pre-drill ball is the LevRg. However, after drill can increase the int diff/MB diff as well.

Asymmetrical shaped core WITHOUT marked MB does not mean it has no int diff/MB diff, can be high can be low, just that the manufacture didn't mark the ball and didn't state the diff.

So when you drill a symmetrical shaped core and spin symmetrically ball and use the pin through CG 6 3/4 to mark a MB to layout a ball, most of the time is a bit meaningless, coz without a weight hole the ending MB will still get close to the thumb hole. Now with a weight hole, when is deep enough, as S^2 stated the ending MB will be in between the thumb hole and the weight hole depends on the size and depth difference of the 2 holes, but still be 6 3/4 away from the pin.

To go in a bit more detail on those numbers, asumming you know what is RG, RG diff is the difference betwen the high RG and the low RG, meaning the RG values betwen the X axis(the axis along the pin) and the Y axis. The Int diff/MB diff is the difference between the Y axis and the Z axis.

I am sure if you have more question you can call Paul and he can explain to you more.
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Laufaye

I understand all that and that's the answer I was expecting; however, I read Paul's response to mean the thumb hole was going to end up being the PSA on virtually any ball -- sym, weak assym, medium assym, just about everything. And if that were true, MB would be hardly relevant at all. If that's not what he was saying, then I misread it.

My point with how the CG related to it is this: On an unmarked MB ball (Storm La Nina, for example), if the pin is over the ring and the CG is in grip center, the MB is going to end up in the track. If you swung the CG out to the right, however, the MB was going to end up near the VAL, because you've changed the vertical line from the pin through the CG by moving one of those two points. MB in the track vs. MB on the VAL *supposedly* yields a noticeably different result, per the manufacturers. So in that case, what you did with the CG did indeed matter somewhat.

Jess

laufaye · « **Reply #12 on:** April 08, 2008, 02:22:56 AM »

quote:
The PSA on a drilled symmetrical ball will be approximetly where the thumb is correct.

The PSA on an assymetrical defined as a ball having an intermediate of higher than 0.010" will approx be in the same spot. However certain higher assymetricals with pin down drillings may shift the low rg axis.

Paul

Jess, I am pretty sure you misread the "same spot", he is talking about the same spot as the mark of the MB.

quote:
My point with how the CG related to it is this: On an unmarked MB ball (Storm La Nina, for example), if the pin is over the ring and the CG is in grip center, the MB is going to end up in the track. If you swung the CG out to the right, however, the MB was going to end up near the VAL, because you've changed the vertical line from the pin through the CG by moving one of those two points. MB in the track vs. MB on the VAL *supposedly* yields a noticeably different result, per the manufacturers. So in that case, what you did with the CG did indeed matter somewhat.

I do not have the actual data with me, if the La Nina is a symmetrical care and spin symmetrically or with a Int diff lower than 0.010, the ending MB will be at the thumb hole area providing no weight hole, hence swinging the CG is not going to have a significant difference, but if swinging the CG far enough to have a weight hole to put in and the hole is deep enough to touch the core then the ending MB will shift towards the weight hole direction.
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Laufaye

n00dlejester · « **Reply #13 on:** April 08, 2008, 05:23:57 AM »

Sooo...let me get this straight, I am a bit fuzzy.

massbiasnomaddah?

If it doesn't matter, why is it even marked? Unlike the CG, it doesn't affect static weights at all.

purduepaul · « **Reply #14 on:** April 08, 2008, 06:34:26 AM »

Jess,

No Let me clarify since you are misunderstood.

I drill an assymetrical ball. The PSA will stay at approximately the same spot after drilling as it spun to pre drill. ALL asymetrical balls should have the MB marked.

Also it is an assumption that the CG and MB are in a direct line all the time.

Author Topic: Does CG maddah when finding unmarked MB? (Read 2949 times)

JessN16

Does CG maddah when finding unmarked MB?

Moon57

Re: Does CG maddah when finding unmarked MB?

purduepaul

Re: Does CG maddah when finding unmarked MB?

spinner031

Re: Does CG maddah when finding unmarked MB?

shelley

Re: Does CG maddah when finding unmarked MB?

dizzyfugu

Re: Does CG maddah when finding unmarked MB?

Strapper_Squared

Re: Does CG maddah when finding unmarked MB?

JessN16

Re: Does CG maddah when finding unmarked MB?

purduepaul

Re: Does CG maddah when finding unmarked MB?

JessN16

Re: Does CG maddah when finding unmarked MB?

laufaye

Re: Does CG maddah when finding unmarked MB?

JessN16

Re: Does CG maddah when finding unmarked MB?

laufaye

Re: Does CG maddah when finding unmarked MB?

n00dlejester

Re: Does CG maddah when finding unmarked MB?

purduepaul

Re: Does CG maddah when finding unmarked MB?