USBC Ball Motion Study

[Brenton_Davy]

Just a little "light" reading on the recent USBC study on ball motion.
http://www.bowl.com/downloads/pdf/ballmotionstudy2007.pdf
I believe there will be a study later that might once and for all bring a result to the "cgnomaddah" debate..............

 

[tonx]

Thanks for the link Brenton.

There are more variables in that particular test to have it be conclusive, starting with the standout few... I don't have time to elaborate right now, but this should entertain discussion with Robbie Buckley and Jason Doust at bare minimum.

Layouts- Layouts directly impact ANY test regarding the cores influence in ball reaction. They used 1 layout for all balls tested, and based the RG, Differential, Z Axis rotation and spin time and differential 'ratio' If the pin position is changed in the test, these values change, and would obviously influence the end result. They use points on page 66 and 67 to value these variables.

End result. If COF and oil absorption are closely related, why does the line graph imply they are not in the ending results? The values only come together in the final Bar graph, if we look at the line graph above it, the 2 values seem almost entirely contradictory.

Finally, what is this test actually giving? Is it the different levels of effect that different variables on the ball have in ball reaction? Scoring? Hit? Carry? it's hard to see exactly what the goal of this study was actually for. If someone else can pick it up in their and point it out to me, that would be great! I understand the overall test is regarding ball motion, but the yardsticks are strange...

I got into a debate with the technical advisor and ball engineer of a ball company about 3 or so months ago. The company claimed to use a certain core shape to control and improve the MOI value of the core (and end result, ball effectiveness) and I argued that although this value has significance independantly, inside a spherical object, not only did I believe a balls effectiveness with a higher MOI value was hampered, that the MOI value had nothing to do with the internal core shape, but the Radius of Gyration of the ball. Without having a physics degree, and little to no time on the spot to do the mathematical calculation for my observation, I left the conversation with neither side conceding the others viewpoint.

In page 13, USBC defines the balls the measurable Radius of Gyration as (MOI/MOB)2, which gives the exact (and definately more precise) value of my observation. This shows that the core shape itself has no influence in the balls ending MOI value regardless of the variable or static imbalances within the ball.

Aussie:1, Yank:0

Australia.... Fork yeah!

It will be interesting to see the ending result if they do choose to raise a study regarding the relevance of effect of the Static weight/CG arguement, but I hope the test is a little more controlled than this one, and takes into account a few different pin placements to give a better overview of the entire study.

Food for thought at least.....

 

[RobbieB]

A couple of observations, having skimmed through the <cough> report. First, Tonx, MOI depends on the internal construction of the ball. core shape affects MOI and thus rg, but the core shape also determines how and how fast the rg changes from one axis of the ball to another. Second, COF and oil abs rate are not necessarily related, and it seems illogical to me to bother testing the effect of oil absorption on a ball that flares! It is very possible that absorbing oil fast is an effect, rather than a cause, of a coverstock type or something that affects performance.

The study really doesn't seem to go anywhere, and I think that the experimenters tried to do too much at once. IMHO, they should have started with one ball, looked at the effect of changing friction by sanding, axis tilt, rotation, pin/pap/cg changes etc. Once they got a handle on how these things affect ball movement, then you can start looking at pairing up different balls. Stuff like rg/mb/diff changes also need to be looked at with the same ball in order to minimise the variables in each test. The point to a true scientific investigation is to keep everything constant EXCEPT the one variable you are testing - a basic concept which appears to have escaped the experimentors in this case.

I'll read it again more carefully later, and have a think. The final results of the study should be interesting, at least. Thanks Brenton.

Cheers, Robbie.

PS: I think Dilbert would say that this is what you get when you let engineers try to do science .

 

[tonx]

A couple of observations, having skimmed through the <cough> report. First, Tonx, MOI depends on the internal construction of the ball. core shape affects MOI and thus rg, but the core shape also determines how and how fast the rg changes from one axis of the ball to another.

I understand what MOI is, my comments were directly related to a marketting gimmick that this particular company uses, claiming that their cores create 20% more inertia than any other company cores out there. The core shape isn't the be all, end all property that dictates the balls MOI, one needs to take into account the densities of the shape (think Brunswicks cores, same shapes different values) to create dynamically symetrical properties, without needing actual symetrical shapes to control what portion of the core is taken out when drilling. One must also take into consideration coverstock thickness, filler density and size of the ball. My overall point to the guy was the 2 values (MOI and RG) are related. He seemed to believe they weren't.

Second, COF and oil abs rate are not necessarily related, and it seems illogical to me to bother testing the effect of oil absorption on a ball that flares! It is very possible that absorbing oil fast is an effect, rather than a cause, of a coverstock type or something that affects performance.

I agree here bud.... However it's not the individual delivery that the value relates to, but rather the balls consistency in reaction each delivery. Ebonite claims they make their covers absorb oil quickly, to improve the consistency in reaction shot to shot. If you check out the www.ebonite.com tech section, it explains their claims here.

The study really doesn't seem to go anywhere, and I think that the experimenters tried to do too much at once. IMHO, they should have started with one ball, looked at the effect of changing friction by sanding, axis tilt, rotation, pin/pap/cg changes etc. Once they got a handle on how these things affect ball movement, then you can start looking at pairing up different balls. Stuff like rg/mb/diff changes also need to be looked at with the same ball in order to minimise the variables in each test. The point to a true scientific investigation is to keep everything constant EXCEPT the one variable you are testing - a basic concept which appears to have escaped the experimentors in this case.
I'll read it again more carefully later, and have a think. The final results of the study should be interesting, at least.

Exactly....

I was hoping you would jump into this topic

Que Dousty now.....

 

[jason_doust]

And ... TA DAAAAaaaa...!! This is too tasty a bait for me to resist.

Well, firstly thanks Brenton! A good meaty read. I almost burned out the bearings in my propeller cap!

Rob, you were close with the Dilbert quote, except that it appears to be what happens when statisticians do science. Regression analysis uses independent variables to assess the value of dependent variables, usually in multivariate scenarios where curves need algorithms to explain them. (You have to love pure mathematics a lot more than me to do this stuff. I should talk to my neighbour Ben.)

Essentially, a bunch of very smart guys using the best equipment they can lay their hands on have discovered that Mo Pinel (of MoRich fame) is right when he says the three most important factors of ball reaction are surface, surface and surface (followed distantly by RG).

At least we have the numbers to back him up now. It's a bit like Samboy's findings in his doctorate thesis a few years ago. Fascinating, but not directly applicable when you're standing on the approach. I am sure that this research will provide the basis for other, more pragmatic findings in the future. But the maths will only get more complex from this point as they introduce more variables like changing the layout.

Cheers,
Jason

p.s. re: "seegeenomaddah..." CG alone doesn't matter. It's how you get it back to legal that matters. Like a hole on the track might make a bit of a difference...

 

[down and in]

hi guys, forgive me if im wrong, but, wasnt this exercise, (dont want to use the word test) covered in BTM a couple of months ago???

an interesting read to determine an unidentified result for an undetermined ball(s). it reminded me of a guy i did physics with, his theory was that the more info, graphs and erroneous calculations you supplied the more it looked like you knew what you were doing..... (he didnt)

i think where they became lost is that they decided to test everything they could think of. hey how about we test this and this and how about that etc.
surprised they didnt test wether the gravitational pull of the full moon affected
the Rg as opposed to a low tide affecting the rollout at 53'

 

[Sumo]

Is this a case of figures don't lie but liars can figure?

There is a huge and unexplained leap from the line graph to the Bar graph.

If I was allowed to run production trials and deliver LOF (leap of faith) results as Gospel truth, in a "believe me, nudge nudge wink wink" way like this report, I'd be rich overnight. Without seeing the 200 linear regressions, you can't possibly accept their conclusions. One of my Professors from Engineering described this type of analysis as Baffle by B-S.

Sumo