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 Post subject: Drilling Angle Greater Than 90 Degrees?
 Posted: Sat Sep 16, 2017 11:24 am Post Number: #1 Post
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Why does the dual angle layout system recommend that drilling angles only be between 10 and 90?

I had one of my balls checked yesterday and the layout was 105 x 3.5 x 55

What is the effect on ball motion when having a drilling angle greater than 90? Is it an even longer skid than a 90 degree angle?


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 Post subject: Re: Drilling Angle Greater Than 90 Degrees?
 Posted: Sat Sep 16, 2017 4:43 pm Post Number: #2 Post
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Mo selected the range to avoid layouts that could result in rolling over holes or reverse flare. If the ball in question is symmetrical the drill angle is used only to position the cg for static weights and/or potential use of a balance hole because the mb after drilling will always be near the thumb hole. I'm not sure about what happens to ball roll on an asymmetrical with a 105* drill angle, but I think it would increase the length of the skid phase. -- JohnP


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 Post subject: Re: Drilling Angle Greater Than 90 Degrees?
 Posted: Sat Sep 16, 2017 4:55 pm Post Number: #3 Post
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Welcome to BowlingChat.

The recommendation is for "Effective" drilling angles. It is a guideline for drillers to start with.

http://wiki.bowlingchat.net/wiki/images ... _Guide.pdf

I need to ask a few questions...

What ball did you have measured?
What is your PAP?
What are your release specs?

viewtopic.php?f=15&t=373

Larger Drilling angles on Asymmetrical balls produce less flare. So depending on a bowlers release spec you could be taking the effect of the core out of the ball motion equation.

Extremely small drilling angles can get the core to rev up before it even hits the lane again taking the core out of the picture as well.

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PAP 4.75" up 1/2"
65* rotation
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 Post subject: Re: Drilling Angle Greater Than 90 Degrees?
 Posted: Sat Sep 16, 2017 8:31 pm Post Number: #4 Post
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105 drilling angle should result in more flare than 90 since it's technically symmetrical at 90 degrees.

Mo and some other expert (paul riidenour if i remember correctly) have said that they believe that the ball revs up faster when the migration of the pap crosses the pin to spin line. 10 degrees is so it has to cross the line and 90degrees is probably the least amount he could assume it crosses that line for higher rev players.

I believe the use of his lower flare drillings which result in 90-120 degree drilling angle is to not make the migrating pap cross the pin to spin line therefore effectively reducing the rev to speed ratio so the bowler can play a straighter line.


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 Post subject: Re: Drilling Angle Greater Than 90 Degrees?
 Posted: Sat Sep 16, 2017 9:58 pm Post Number: #5 Post
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gunso wrote:
05 drilling angle should result in more flare than 90 since it's technically symmetrical at 90 degrees.

Take a look at the low flare layout D on Mo's drilling sheet for the Cash, 90-2.25-50 P1

http://radicalbowling.com/uploads/downl ... ctions.pdf

The post drilled Int. Diff .024 is no where near being Symmetrical.
The larger drilling angles on Asyms have flare characteristics like Symmetricals. It doesn't make them Symmetrical.

With the example of the O.P. even if this was from an Asymmetrical ball the thumb hole will pull the PSA towards it unless it was a Very Strong Asym to begin with.
I am still curious as to what ball this layout is on. Modeled from my PAP the pin to PSA line crosses through my grip center. If its a Symmetrical ball it wold be a good candidate for a Mo-Hole.

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12* tilt
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16mph off hand


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 Post subject: Re: Drilling Angle Greater Than 90 Degrees?
 Posted: Sat Sep 16, 2017 10:59 pm Post Number: #6 Post
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what I meant is flare wise it works as a symmetrical. with a 90 degree drill angle there is no assymetry making it flare more. I know that the assymetry of the ball is still in the ball and that it should make the hook phaze shorter than a symmetrical


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 Post subject: Re: Drilling Angle Greater Than 90 Degrees?
 Posted: Wed Sep 20, 2017 4:50 pm Post Number: #7 Post
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One reason I believe Mo selected 90* as the max recommended drill angle is that puts the PSA 6 3/4 from the PAP. Going <>90* puts the PSA closer to the PAP. Smaller angles put the marked side of the PSA closer to the PAP, larger angles would result in the the opposite end of the marked PSA being closer to the PAP.

As far as the flare, the Blueprint Track Flare Study showed us that with a 90* drill angle there is virtually no difference in shape of the graph of the effect of Pin-to-PAP distance on track flare between a strong asym cored ball, a mild asym cored ball, and a sym cored ball. The flare peaks at 4 1/2 and goes down slightly at lesser distances and steeper at longer distances.

And as Gunso pointed out, Mo et al. believe that the rev rate of the ball increases as the PAP migrates past the Pin-to-PSA line, so the further that line is away from the initial PAP, the more delayed the increase in rev rate will be.

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