Any idea, how CATS calculates rev rate? I know it doesn't measure it, since it only uses ultrasonic sensors that only measure on what board the ball passes the sensor.

It probably does some kind of calculation based on energy conservation, right?

I have no clue how cats works, but I may have some input to this discussion.

Let's check our terminology first before we go too much farther, I think there is some confusion with the term "roll" as it relates to bowling. Keeping in mind there are a very few number of physicists in bowling, so the term may need to be changed to keep things scientific let me put the bowling terms in play and maybe Mark can input the physics so we can follow a bit better.

1. When a bowler lets the ball go he/she imparts a certain amount of axis rotation and tilt to the ball

2. The ball then enters the "Skid" phase as it passes through the oil. The ball will skid until it encounters enough friction to cause the ball to

3. "Hook" during this phase the ball changes direction from going away from the pocket to turning back in the direction of the imparted side rotation.

4. The Roll Phase happens when the ball has started rolling in the direction of the side rotation. I think this is the point of confusion as the ball still is hooking in this phase.

5. Hook out happens when the ball has used up all of it's side rotation, but not it's tilt. In this phase the ball starts to lose it's tilt and is it's most powerful at the pins with the least amount of deflection.

6. Roll out when this happens the ball has lost all of it's tilt and is at it's weakest.

If a ball hits the pocket in the roll phase the ball can drive the head pin off the two pin, and take out the 5 before the ball can hit it, since the 5 pin is gone, the ball can't deflect off of the 5 and finishes to the left of the 9 pin, sometimes leaving the fast 8 or solid 9 pin.

If a ball hits the pocket in the roll phase (still skiding and hooking) and the ball doesn't bounce the head pin off the two into the 5 before the ball hits the 5, the ball will hit off the 5 and deflect to the right of the 9 pin spot, the 9 is usually gone because the ball deflects off the head pin into the 3 that bounces off the 6 and takes out the 9 before the ball gets there, in this scenario there is a 50/50 chance for a strike, or a 10 pin depending on if the 6 touches the 10.

If the ball hits the pins in a roll out scenario the ball has no energy left and bounces hard off the head pin into the 3 which drives the 6 into the channel next to the 10, the ball trails off to the right of the 9 pin, sometimes leaving an 8-10 split.

If the ball hits the pins as it hooks out, the ball will deflect the right amount into the 3 pin which will bounce into the 6 and then into the 9 before the ball gets there again, the 6 will go straight into the 10, the ball will deflect off of the 5 and knock it into the 8 pin and then finish square on the 9 pin spot.

I am not a physicist if anything I just said is wrong according to physics, feel free to let me know.

The above information I have gleaned over the years by reading books, magazines, web pages and personal experience, but nothing scientific since none of the books were written by scientists, but the above is what they teach us to teach others, so if it's wrong I would like to know.

Nice, great description from the bowling end. Here's what I can add to this.

2. Skid Phase - Pretty obvious, the ball is skidding and the translational velocity is greater than the rotational velocity.

3. Hook Phase - Ball hits friction down lane, again obvious. Friction does 3 things, besides turning the ball in the direction of the side rotation, it also causes the ball's translational velocity to drop and rotational velocity to increase, due to conservation of energy.

4. Roll Phase - This is where the confusion is happening. At this point, the ball is rolling in the direction of the side rotation, but it's not pure rolling motion in the sense of physics. The ball is still increasing its rotational velocity as friction keeps on slowing the ball down, so it is still hooking.

5. Hook Out - Now, the ball's found the correct balance between the rotational kinetic and translational kinetic energies, so the ball is no longer hooking, it's rolling, but the axis tilt does play a huge role, I'll describe this in the roll out section.

6. Roll Out - The difference between 5 and 6 deals with what is known as angular momentum. Angular momentum is a very complicated topic, so I will try to keep it simple. Angular momentum is the momentum due to a rotating object. It is strange in the fact that the angular momentum acts in a direction that is perpendicular to the radius and the rotation. If we think of a yo-yo, the angular momentum acts out of the side of the yo-yo, to the left or to the right depending on the direction of the rotation. If you try to tilt the spinning yo-yo, angular momentum keeps it spinning on the same axis. Now, when a bowling ball loses axis tilt, it's angular momentum changes, not in size, but in direction. If the axis of rotation changes orientation, the angular momentum also much change. For a bowling ball, this change in angular momentum creates a force that flattens out the roll of the ball, thus making it weak. There's a very dramatic example of this. If you sit on a rotating stool holding a rotating bicycle wheel out in front of you so the wheel is vertical, nothing interesting happens. If you tilt the axis of the bike wheel so the wheel becomes vertical, depending on the direction of rotation of the wheel, you will both feel a force in your arms trying to prevent you from doing this and also, the stool you are sitting on will turn. If you tilt the axis the other way, you will feel the same thing and the stool will now rotate in the opposite direction.

Mark

Oops, in number 6, meant to say that you tilt the axis of the bike wheel so it becomes horizontal.

Mark

Thanks, I like the bicycle tire reference, so when the ball hits the pins as it is losing tilt the ball will lean in towards the pins which enables it to carry better.

If I have this straight, a pin axis drilling the ball will tend to get to the roll out phase faster, and a high rg drilling will tend to stay in the skid and hook phase longer?

From what you described, I'd say that hook out provides the correct amount of deflection, which is why the carry would be good. We all know that too much or too little can be bad. The bike wheel demonstration is one of my all time favorites. Students are quite shocked to see what happens, and then also shocked to feel the force needed to change the axis of rotation from horizontal to vertical.

What you said about pin drilling and high RG is correct. Because the pin drilling revs up quicker, it goes through the whole scenario quicker than the high RG drilling. This is also why tight rope walkers carry long metal poles. It increases their RG, making it harder for their body to rotate away from vertical.

Mark

I'm thinking because the low rg drilling would not flare so much that it would go too long before it started it's progression. I am also thinking a pin axis drilling should be best used on lanes with extremely jumpy back ends, not short patterns because the ball will burn out. High axis rotation and high rev bowlers might also get some use out of pin axis drillings on normal house patterns.

Thanks for the physics lessons

No problem, now if only another group of people that I teach would be as appreciative.