Explaining bowling ball specs

[fordman1]

Just teasing Mike. All that technical stuff is hard to understand. Remember most of us are once or twice a week league bowler. We go to the pro shop and say give me a strong ball that goes long or what ever our choice is. My eyes glaze over when I read to much tech. You could make up this stuff and most of us wouldn't know the difference.

I have done that with numbers and names. Ernie Kabonze was the 1st bowler who did this or that and no one ever questioned it. Pulled it right out of my A$$.

I was just having a little fun.

[Mike White]

Just teasing Mike. All that technical stuff is hard to understand. Remember most of us are once or twice a week league bowler. We go to the pro shop and say give me a strong ball that goes long or what ever our choice is. My eyes glaze over when I read to much tech. You could make up this stuff and most of us wouldn't know the difference.

I have done that with numbers and names. Ernie Kabonze was the 1st bowler who did this or that and no one ever questioned it. Pulled it right out of my A$$.

I was just having a little fun.

All that technical stuff is fairly basic math.

That reminds me of my neighbor who wanted to get into the local pipe fitters union.

On the entrance test they had some basic math questions. Mostly about converting fractions into decimals, and reverse.

This guy previously was a carpet layer, so using a tape measure wasn't something he had trouble with.

He failed on the first try, so he asked me for some tutoring.

When I looked at his sample test, I said "This test is culturally biased".

It was biased against the culture of students that didn't pay attention in math class.

He passed just fine on the second try, and is now 2 years into a 5 year stint of apprenticeship.

[classygranny]

1 mile = 5280 feet = 63,360 inches.

The circumfrence of a ball is about 27 inches, (effectively less as you increase axis tilt)

63,360 / 60 (convert to minutes) / 27 (convert to revolutions) = 39.111

A ball rolling 1 mph, will have a rev rate of 39.111 rpm

When you release the ball, it will most likely have more forward speed than equivalent rev rate.

The ball senses friction from the lane causing it to slow down, but since the direction of the friction force is not directly thru the center of the ball, it causes an increase in rev rate.

The best analogy is an airplane tire when it's landing, before contact the wheel isn't spinning as fast as the plane is traveling forward.

When it does make contact, friction causes the wheel to increase it's rev rate until it matches the planes speed.

Take whatever speed the ball is at as it enters the pins, multiply by 39.111, and you have a good estimate of the rev rate as it enters the pins.

This of course assume you threw the ball in a way that it will roll before hitting the pins.

So if your ball speed is only 14 mph at the pins, you have approximately a rev rate of 547? Seems like a high rev rate to me, but since I really don't know if this is mathematically correct, I will assume so.

[djp1080]

So if your ball speed is only 14 mph at the pins, you have approximately a rev rate of 547? Seems like a high rev rate to me, but since I really don't know if this is mathematically correct, I will assume so.

Yes, that's the kind of number I get when I put in my estimated ball speed at the pins...
Now we need to see if we're actually using the full circumference of the ball. Probably not!
So the magic formula for the casual bowler isn't quite 39.111 now, is it?
Thanks for the pretty good explanation though Mike...

[bowl1820]

So if your ball speed is only 14 mph at the pins, you have approximately a rev rate of 547?

Yes, It's because the rpm's are calculated differently at that end of the lane.

It's why when you look at the ball motion chart it shows max rev's in the roll phase. (Look up the USBC Ball motion study and you can find the math about it.)

Seems like a high rev rate to me, but since I really don't know if this is mathematically correct, I will assume so.

MO Pinel had rule of thumb to approx. it, you add about 50% the rpm's you have in the heads (EX. 300 rpms in the heads becomes about 450 rpms at the pins.)

To really calculate it accurately , you need to know where the ball actually starts the roll and get the distance from there to the pins and the time it took to travel that distance, so you can figure out the exact speed. Then calculate the rpms.

[Mike White]

So if your ball speed is only 14 mph at the pins, you have approximately a rev rate of 547? Seems like a high rev rate to me, but since I really don't know if this is mathematically correct, I will assume so.

You're used to associating the ball speed at release with the rev rate at release.

So yes, 14 mph with 547 rpm at release would be a very high rev rate.

The question was when the ball rolls.

If you release the ball at 14 mph, and a rev rate lower than 547, when the ball encounters friction, the speed will decrease, as the rev rate increases until the rev rate (in rpm) is 39.111 times the speed (in mph)

[Mike White]

Yes, that's the kind of number I get when I put in my estimated ball speed at the pins...
Now we need to see if we're actually using the full circumference of the ball. Probably not!
So the magic formula for the casual bowler isn't quite 39.111 now, is it?
Thanks for the pretty good explanation though Mike...

The circumference of a circle is 2 * pi * radius.

The radius of the ball at 0 degrees of tilt is 4.2972.

As you increase tilt, the radius of the circle on the surface of the ball that contacts the lane is 4.2972*cos(tilt)

So the full calculation of the MPH to RPM is RPM = MPH * 63360 / (2 * pi * 4.2972 * cos(tilt))

[Mike White]

Yes, It's because the rpm's are calculated differently at that end of the lane.

It's why when you look at the ball motion chart it shows max rev's in the roll phase. (Look up the USBC Ball motion study and you can find the math about it.)





MO Pinel had rule of thumb to approx. it, you add about 50% the rpm's you have in the heads (EX. 300 rpms in the heads becomes about 450 rpms at the pins.)

To really calculate it accurately , you need to know where the ball actually starts the roll and get the distance from there to the pins and the time it took to travel that distance, so you can figure out the exact speed. Then calculate the rpms.

There are three pieces of text in that graph that are just plain wrong.

Hook Phase - Force created by the rev rate exceeds the force created by ball speed.

Skid Phase - Force created by ball speed exceeds the force created by the rev rate.

Transition from skid to Hook - Force from speed = force from revs.

In the skid phase, the ball isn't slowing down, and isn't changing direction.

Force = Mass * Acceleration.

If there isn't any acceleration, there is no force.

So force from ball speed = force from rev rate all thru the skid phase, and also all thru the roll phase.

At the beginning of the hook phase, the force from ball speed will exceed force from rev rate.

At the end of the hook phase, both the force from ball speed, and force from rev rate will reach 0.

A ball in the roll phase is not accelerating, and not changing directions so F = M * A says force = 0.


You don't need to know exactly where it rolls, only that it does roll.

Using conservation of momentum, you can calculate the momentum at the release of both the ball speed, and rev rate (requires knowing the RG of the pap), then realize that momentum will still be the same as it hits the pins.

The amount of momentum that is lost due to speed, is gained due to increased RPM.

There will be only one MPH and RPM combination that both meets the proper ratio (for a given axis tilt) and conserves the total momentum that was present at the release.