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 Post subject: How to locate the gradient line on a symmetrical ball
PostPosted: Sun Dec 19, 2010 8:40 pm 

Joined: Thu Aug 27, 2009 10:43 pm
Posts: 1698
Location: Rochester NY
I have had several questions regarding how to locate the gradient line on a symmetrical ball.

I spoke with Mo about Symmetrical P-Hole locations, and this is what I came up with as a result of that conversation, the 2 different techniques to locating the gradient line.

Image
On the GT1(Grey) I used a line .5" parallel to the left of the grip centerline, and placed P4 where a 6 3/4" arc centered on the pin intersects that line.

On the TR2(Blue) I used the "projected PSA" of a line from pin through CG and placed P4 at 6 3/4" from the pin.


You use "projected PSA" when you wish to create an earlier reaction with smaller drilling angles because this moves the PSA further from the thumb.

You use the parallel method when you wish to have the ball react a bit harder after the hole is drilled.


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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Sun Dec 19, 2010 9:45 pm 

Joined: Thu Jul 02, 2009 4:01 pm
Posts: 526
Thank you for this info. I will keep these concepts in mind when I drill sym-balls in the future. You da' man, JW !!!

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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Sun Dec 19, 2010 10:03 pm 

Joined: Tue Aug 31, 2010 6:26 pm
Posts: 77
question...on the gt1...is there ever any use to drill the P4? It's under the thumb isn't it? This is very interesting!!! Help me to understand the use of the P4 drilling? And on this one it looks like the P3 could be a double thumb. Right or wrong? I really don't know. Just asking.

Jim Hud


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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Sun Dec 19, 2010 10:48 pm 

Joined: Thu Aug 27, 2009 10:43 pm
Posts: 1698
Location: Rochester NY
The double thumb layout has more requirements than just the weight hole location. It is a specific formula for maxing out the after drilling specs.

The placement of the hole modifies the differential in this manner:

P1: 20% Decrease
P2: No change
P3: 20% increase
P4: 40% increase, but up to 55% increase depending on the core.

As far as the P4 application in the parallel method, most of the time a P3 or P3.5 hole would be appropriate, generally you won't need that P4 hole. If you need the strength, it would be better to use the projected PSA method to intensify the reaction.

You want to try and match the layout as best you can prior to drilling, and use a hole to fine tune. Some layouts you use with the intent of a strong hole.


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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Mon Dec 20, 2010 6:00 pm 

Joined: Tue Aug 31, 2010 6:26 pm
Posts: 77
so on the gt1 the p2 still does nothing other than USBC weights? So is the P3 still going to be 20% or is it going to be like a P4?


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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Tue Dec 21, 2010 1:29 am 

Joined: Thu Aug 27, 2009 10:43 pm
Posts: 1698
Location: Rochester NY
P2 will have an inconsequential impact on reaction. I know it seems counter intuitive to have 2 spots that will do that, but remember you are moving the PSA in a couple of different ways.

The trick with symmetrical balls is more about moving the PSA, not intensifying it like with asymmetrical balls.


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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Tue Dec 21, 2010 1:24 pm 

Joined: Wed Sep 22, 2010 12:14 am
Posts: 804
Location: Iowa Falls, IA
What happens to the gradient line when using smaller drill angles, say 45 and under? At what point does the distance between the PAP and the assumed PSA become small enough to blur the distinction between these points? I suppose, using smaller drill angles in symmetrical balls aren't nearly as important as pin/pap lengths, but even with drilling a ball for control and even energy bleeding, how can you keep a hole that might be necessary for static weights from mucking up your intended reaction?

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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Tue Dec 21, 2010 6:14 pm 

Joined: Thu Jul 02, 2009 4:01 pm
Posts: 526
Drilling angle on a symm ball ranks down the list of importance.

1) Surface, Surface, Surface
2) Pin / PAP distance
3) VAL angle
4) X-Hole Placement
5) Drilling angle

Discussed these variables w/the Zen master, Justin, and this is what he came up with . . and after examining all my symm balls I would have to agree. So when drilling a symm ball it is likely best to focus on the first 3 and let the last 2 fall where they may. Just my $.0375 worth ($.02 adjusted for inflation)

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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Tue Dec 21, 2010 7:32 pm 

Joined: Tue Aug 31, 2010 6:26 pm
Posts: 77
very good thanks for the info

jim hud


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 Post subject: Re: How to locate the gradient line on a symmetrical ball
PostPosted: Tue Dec 21, 2010 9:24 pm 

Joined: Thu Aug 27, 2009 10:43 pm
Posts: 1698
Location: Rochester NY
plamormick wrote:
with drilling a ball for control and even energy bleeding, how can you keep a hole that might be necessary for static weights from mucking up your intended reaction?


A P3 or P4 hole used in this instance will tweak the differential ratio and create a smoother earlier reaction. That would seem to serve the same ends to me.

The primary purpose of drilling angle in symmetrical balls is to prepare for placement of a hole. I posted on this in another thread and dug it up:


JustinWi wrote:
The main purpose of a drilling angle in my findings is to control weight in order to facilitate the placement of a hole to retain static legality.

Generally I'll start with one of these options:
40 for a pretty large hole.
60 for a medium or small hole.
75 for no hole.

I'll chose out of box pin length based on what position I want to use. Most frequently I'll make use of a 3" or 4" pin.

After drawing lines I can weigh and potentially tweak.


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