Check out my unique way of finding the preferred spin axis (PSA) of a bowling ball

[sprocket]

Maybe I should have posted this in the video forum but here it is anyway. This video shows a unique, maybe crazy way I discovered to find the PSA of any bowling ball.

PSA stands for preferred spin axis and in an asymmetrical ball it is very close to being the same as the mass bias which is marked on the ball. In a symmetrical ball the PSA is usually pretty close to the thumb hole, although a balance hole can shift it.

Here's the video:
http://www.youtube.com/watch?v=-WIfDXDAloQ

[MICHAEL]

American ingenuity, never fails to AMAZE me!!! Thanks... great post!! Did this come to you in a dream....lol.... iceman... Very COOL!!!!

[sprocket]

Well one day, long ago, with a different washing machine, I was loading clothes and I thought "I wonder if I could spin a bowling ball on the agitator?" Now, why would I want to do that? Well, if it spins and stays there, I can use it as a ball spinner and resurface bowling balls. What I noticed is that sometimes the ball spun nicely and sometimes it wobbled like heck. I came to realize that if I put the thumb hole up or down the ball balanced itself quickly.

The only problem with resurfacing was that my only options were thumb hole up or thumb hole down. I couldn't split the ball in quarters because if I put the thumb hole to one side it would either migrate to the top or the bottom. As I learned more about dynamic balance and cores and such I came to realize the ball was finding its preferred spin axis.

Notice that with the asymmetrical ball in the video the PSA I found was slightly above the marked mass bias towards the thumb hole. This makes perfect sense because even in an asymmetrical ball with a strong mass bias, the thumb hole will still have a slight effect on the PSA.

[bowl1820]

Well if you bolted a small mixing bowl to the agitator cap you might get away with using that as a spinner.

As for finding the psa, the determinator has nothing to worry about! Lol

[Aslan]

So...can I use my ball spinner as a clothes washing machine???

How bout THAT ingenuity Iceman!!? You're welcome.

[MICHAEL]

So...can I use my ball spinner as a clothes washing machine???

How bout THAT ingenuity Iceman!!? You're welcome.

Sure you can Aslan!!! but only the spin cycle!!! LOL
It did a nice job, but made a mess!! What,,, are those my alter ego underwear that my wife got me?????

[sprocket]

Well if you bolted a small mixing bowl to the agitator cap you might get away with using that as a spinner.

As for finding the psa, the determinator has nothing to worry about! Lol

I'm getting repeatability within 1/4" or less. I wonder if the Determinator can actually do any better? Of course the Determinator also measures spin time, which has immense value.

I don't know if my method actually has any value at all other than just for fun. Yes it finds the PSA, but so what? Is there a benefit to knowing where it is?

[ggranger97]

Wow very interesting! New here and impressed

[sprocket]

Interesting. I tried finding the PSA on an original Blue Hammer. This ball has been redrilled once and I can't locate the pin. I understand that the pin is the same color as the ball and can be hard to find and that almost all of these balls were pin-in as pin-outs were considered blems. With a pin-in ball there is no mass bias so the ball shouldn't be able to find a single PSA. It should be happy to spin close to wherever it is currently rotating.

So my test showed that it would find a PSA near where it was already orientated. It would wobble some but would find a PSA in the vicinity of where it started. I never got the same results twice.