I am wondering what ball you would recommend for a pin on the axis drilling. As I understand it this will basically make the balls response only a factor of cover, speed and revolutions.. It will take the core out of it.
Also, would a symetrical ball be better than an assymetrical..
just off the top of my head I am thinking Hammer Anger...strong cover.. can change the cover pretty easily.
Or maybe a urethane.? not sure
any other ideas.

What lane conditions do you want the ball for?

The closest you should put the pin to the pap is 1 1/2", this is because if you vary your release, the pin could move past the axis and cause the ball to back flare over the thumb.

Urethane balls usually = 3 piece core unless you get the lane #1 liberator. Asymmetrical balls are less stable than symmetrical balls, but that's not to say that asymmetrical balls are not good for pin axis drillings, they are just a bit stronger.

Just keep in mind the back end on a pin axis drilled ball will most likely not be enough to cover tons of boards so you will need more help from the ball if you want the ball for heavy oil and screaming back ends you will need a stronger ball, if you are looking at a ball for the viper or cheetah then a good medium solid ball or medium strength pearl will probably work well for you.

looking for it for more of a pba or sport shot..
so you think the anger would be a good ball.?. or maybe one of the vibes..
I know most about what Hammer has to offer that is why I threw those out there.. if any others come to mind let me know.

Pin axis will also put the ball in its low RG state, which will make it hit the pins with less inertia, causing more deflection. If you put the pin 6 3/4" away from the PAP you will get the same neutralization of the core, with a higher RG so that the ball will have less deflection.

I'm glad you said that .. that was my next question.. I know 6 3/4 is another stable position...
so you are saying I should get a low rg ball and put it at 6 3/4 .. are there any balls where the high rg is as low as some balls low rg ??

also if the pin is 6 3/4 even though it is stable.. won't the ball still want to Flip when it hits friction or won't the core want to try to lay on its side just because of gravity..

Many balls' high RG are lower than other balls' low RG. Some manufacturers list RG as the average, and some the low. In any case, low rg + diff = high RG. The Total Inferno has a low RG around 2.46 and a diff around 0.05, which makes the high RG around 2.51. You would be hard pressed to find a Lane Master ball with a low RG lower than 2.51.

I think Mkirchie needs to get in on this conversation to get us more insight as far as downlane reaction. I don't think it would Flip because of the core position if it was actually at 6 3/4", or even if it was very close. However, being in its high RG state might affect things - when it hits the friction, it would tend to lose speed and add revolutions, and being in a higher RG state vs. a low RG state would change the physics involved in that reaction. How? My guess is that the higher RG state would resist the addition of revs, so you'd... lose more speed? Would it be significant? I don't know.

the lose speed and add revolutions.. that is the part I am talking about.. if it will do that.. and if it does I think the adding rev is because the core is flipping over to roll on its high rg axis..
when you release the ball the 6 3/4 core position is standing up in relation to the force.. so therefore that wants to keep the balls revs down..(for that given force) as the core shifts to a lower rg then the ball can rev up (from that given force)..

much like an iceskater spinning with arms extended going slow and then tucking them and spinning fast.. same force but different rg..

that is what goes on normally with a bowling ball( i think)..
if that is what would still go on with the core at 6 3/4 inches.. i dont know..

The ball will not Flip from a low RG axis to a high RG axis. These axes are the two most stable positions for the ball to be in. If the ball in in the high RG position, it will stay there, like a football that has been kicked off end over end. If the ball is in the low RG position, it will stay there like a football in a spiral. To change from one to the other, it changes from stable, to unstable, back to unstable, which it won't do. Not only that, but it would pick up revs if it could Flip to the low RG axis, not the high one.

I have more to say about this whole topic, but don't have time now, I'll post again a little later.

Mark

The added revs come because as the ball is traveling down the lane, it is not spinning as fast is it would be if it were rolling.

The circumference of a ball is about 27 inches. Say someone throws the ball with 300 rpms, at 18 mph, off their hand, and their axis tilt is near 0 (so we can use all 27" of surface). Converting to seconds, we have 5 revolutions per second, and 26.4 feet per second of speed. 5 revolutions equates to 135 inches, or 11.25 feet of ball surface. So you can see that the ball surface rotation is less than 1/2 of the speed that the ball is actually traveling.

When the ball hits friction, it will need to even those 2 numbers out to get into a roll. As you know, the ball doesn't slow down that much - an 18 mph ball can be expected to end up around 15mph at the pins. That's only a 1/6 reduction in speed. So the ball must "rev up" to get into its roll - a fully rolling ball at 15 mph will be rolling at 9 7/9 revs per second, or 587 rpm. So you lose about 13% of your speed, but your revs increase by 95% (in my hypothetical, but plausible scenario).

Now, back things up to the foul line. Your hand will apply the same force to the ball, so a higher RG drilling will have slightly less revs off your hand. So when the higher RG drilling hits the breakpoint, it will have a lower ratio of revs to speed than a lower RG ball would have, so I would think that would translate into a more energetic reaction. In addition, the ball will resist the addition of revolutions due to its higher RG state, so it would probably lose more speed, which might allow for more overall hook.

If you were going to try with an asymmetrical ball, it would be interesting to see the flare difference between pin at 6 3/4" and MB on PAP, vs. MB at 6 3/4" and pin on PAP. Actually, it'd be interesting to see the difference in pin on PAP vs. pin at 6 3/4" on a symmetrical ball as well, instead of this theorizing. A high differential core would do a better job of displaying the difference.

EDIT: Yay, Mark found this thread. I very much look forward to his post.

I don't really have too much to add, your description is really good, in fact, it mirrors what I was going to say. I just want to make a few comments.



That scenario is plausible, but I'd have to say it's not desirable unless you're trying to use it to your advantage. At that point, the ball would be in a pure roll which would be the same as a ball that is rolling out, it's done increasing it revolutions.



Exactly right on the second part, but I wouldn't necessarily say that it is more energetic, it can be explained through conservation of energy. When the ball leaves your hand, you have dictated the total amount of mechanical energy it will have, which is the sum of the rotational kinetic energy (RKE) and the translational kinetic energy (TKE). As the ball goes down lane and hits friction, the ball loses speed and thus loses TKE. It increases revolutions to increase the RKE to keep the total energy the same. Since a high RG drilling resists the increase in revolutions more than a low RG drilling, it will take longer to increase its revolutions and RKE, so the ball loses more speed and more TKE than a low RG drilling would, but the total energies in both cases will not change. Assuming equal surfaces, the speed for both balls decreased at the same rate, it's just a matter of when it stops decreasing. So, where the ball is at the point of reaction in reference to the pins determines how you want the ball to react to get the most punch to the pins, quicker with the low RG drilling or slower with the high RG drilling? To me, it depends on your game and the lanes.

As for the difference in the loss in speed, I'm going to post on that later, I can crunch some numbers, but I kind of want to drive home first. On a side note, I think that this discussion is also illustrating the importance of your ball speed matching up to your rev rate.

Mark