Designing and building ball roundness tester

iusedtoberich · Sep 7, 2020

I'm working on a ball sphericity (roundness) tester for fun. Below are a couple of pictures, and a YouTube video link describing the process. I'll update as I go.

My motivation is to see how different ball sets and brands compare both when new, and when worn. Also because I like making things.

Youtube video with a lot more detail. Part 1:
https://youtu.be/fHgEgi62nO0

justnum · Sep 7, 2020

i saw mythbusters

they did the golf ball test

that is what I was thinking to check for dynamics

access to such equipment is not possible

at the local school the best was a fancy fan

at home the best I had was visual inspection.

my interest was how much cracking can it have and still maintain normal behavior

cue balls shed and chip I am still weathering mine down. not so much since Ive been busy working

jimmyco · Sep 7, 2020

Things many of us have in the garage/shop:

Scrap of wood.

Hole saw.

Digital tire tread gauge.

ideologist · Sep 7, 2020

iusedtoberich said:
I'm working on a ball sphericity (roundness) tester for fun. Below are a couple of pictures, and a YouTube video link describing the process. I'll update as I go.

My motivation is to see how different ball sets and brands compare both when new, and when worn. Also because I like making things.

View attachment 556942

View attachment 556943

Youtube video with a lot more detail. Part 1:
https://youtu.be/fHgEgi62nO0

Fantastic, I can't wait to see the end result

TATE · Sep 7, 2020

iusedtoberich said:
I'm working on a ball sphericity (roundness) tester for fun. Below are a couple of pictures, and a YouTube video link describing the process. I'll update as I go.

My motivation is to see how different ball sets and brands compare both when new, and when worn. Also because I like making things.

View attachment 556942

View attachment 556943

Youtube video with a lot more detail. Part 1:
https://youtu.be/fHgEgi62nO0

That is exciting.

One more suggestion for next project: As a business proposition, what the world needs is a good, affordable ball cleaner and polisher. It should be able to handle 16 balls, not be ridiculously loud and cost around $200. I think you would sell a lot of them.

garczar · Sep 7, 2020

Should be able to 3d print a go/no-go gauge pretty easy. Back when golf balls got out-of-round we carried one clipped to our bag. Those were metal but 3d printing one should be fairly simple.

Don Owen · Sep 7, 2020

Roundness

Balls can be perfectly round and not play well. If the weight is not distributed uniformly they will roll off significantly.
—Don

iusedtoberich · Sep 7, 2020

TATE said:
That is exciting.

One more suggestion for next project: As a business proposition, what the world needs is a good, affordable ball cleaner and polisher. It should be able to handle 16 balls, not be ridiculously loud and cost around $200. I think you would sell a lot of them.

I was thinking about this a few years back. Plus see if they can be made smaller. But its a lot of work, and may have to be injection molded with associated tooling costs to get the cost reasonable. Designing for injection molding is my day job, but I just don't know if the payback would be there. It would have to be made in China, and shipped over. Maybe in another life...

iusedtoberich · Sep 7, 2020

garczar said:
Should be able to 3d print a go/no-go gauge pretty easy. Back when golf balls got out-of-round we carried one clipped to our bag. Those were metal but 3d printing one should be fairly simple.

The go/no-go gauge is more for diameter tolerance. This device won't be able to measure diameter. I'd have to do that separately with the micrometers. What it would easily measure is deviations from true roundness at different parts of the ball. Also it would be able to measure any defects such as sunken-in numbers.

The deviation I expect per ball is in the range of .001" to .002", or even less.

iusedtoberich · Sep 7, 2020

Don Owen said:
Balls can be perfectly round and not play well. If the weight is not distributed uniformly they will roll off significantly.
—Don

Agree. In addition to measuring diameter and roundness, I would also measure mass. And for the distribution of mass, I was thinking of doing some sort of ramp test, to see if the balls roll true. Especially in light of some recent balls rolling off. But, this has all been in my head for the past 8-10 years, so it may never see the light of day....

Its a lot of effort, for what will probably be very little difference between balls.

iusedtoberich · Sep 7, 2020

jimmyco said:
Things many of us have in the garage/shop:

Scrap of wood.

Hole saw.

Digital tire tread gauge.

I've been using tools since I was 4 years old

For my 6th birthday I got a toolbox and hammer that I still use today.

justnum · Sep 7, 2020

How about the jelly mold test?

submerge half the ball in a resin or jelly or material of choice

I find studying a mold to be as useful as the original object

The main advantage is not breaking the one cue ball I own.

However the futuristic apparatus you have design sounds exciting?

The only other shape with rolling properties similar to a ball is a convex body of constant width. A comparison of roundness would be better than a profile of products that are nearly identical, except in their manufacturing process.

I bring it up because I am showing off. And because it can provide nice benchmarks, without a control your study would be circular.

Plus I need to promote geometers because I can include some additional tidbits about being round in the academic way. Which I will refrain from because you have shared those precision measuring devices, that is exciting to see.

Also I was hoping to design silent billiard balls, my neighbors complain alot. Or at least dampen the noise. conserving that energy could be interesting, I'd hate to lose energy to useless acoustics. who can recognize how billiard balls collide by ear, thats like major billiard gear head stuff.

Bob Jewett · Sep 7, 2020

iusedtoberich said:
I'm working on a ball sphericity (roundness) tester for fun. Below are a couple of pictures, and a YouTube video link describing the process. I'll update as I go.

My motivation is to see how different ball sets and brands compare both when new, and when worn. Also because I like making things.

View attachment 556942

View attachment 556943

Youtube video with a lot more detail. Part 1:
https://youtu.be/fHgEgi62nO0

The owner of Sequoia Billiards had a ball gauge with an indicator. I believe the three resting points were some kind of bearing so they rotated easily rather than slid on the ball. I wasn't paying enough attention to notice how precise the feeler gauge was. It was really quick to tell how good a ball was.

About 1975 I got the Student Union maintenance guy to make me a go/no go two-hole round gauge. You're right that it can't measure diameters directly, but it can find significant non-sphericity. At the 1976 World Open, the balls were rolling funny and it turned out that many of the eyes of the 3s, 5s, and 7s were bulging enough to hang up on the 2.255 hole :yikes:. (+- 0.005 is the actual spec, but most balls these days seem to be close to +-0.001.)

The indicator-based gauge is a lot more flexible, but a piece of steel with two holes drilled through it (or EDMed?) is a lot more rugged if you're dragging it to tournaments.

Do you need a known good ball to zero the feeler each time?

Here is a set of round gauges for pool balls from Ebay for $13 from seller joebuyer -- he has one set left on the current auction. The five sizes relative to 2.250 are +0.005, 0.000, -0.005, -0.010 and -some_more. They're made of 1/16" fiberglass. The undersized holes are to see just how badly worn the balls are.

For those who think the diameters of a sphere tell the whole story, check out this video about a constant-diameter "sphere" that is clearly not round: https://www.youtube.com/watch?v=fOojOfpcPZM

Bob Jewett · Sep 7, 2020

For the balance test (center of gravity = center of sphere) you might be able to do a spin test. I think you only have to test two axes.

I think the ramp roll test requires three separate runs for the three axes.

justnum · Sep 7, 2020

Bob Jewett said:
For the balance test (center of gravity = center of sphere) you might be able to do a spin test. I think you only have to test two axes.

I think the ramp roll test requires three separate runs for the three axes.

clear lexan board billliard ball sandwich, clear lexan so you can film and monitor contact points

sandwich the billiard balls maybe put some sand or ink some type of dye to help indicate where the cracks are

I think jet liners use the special chem for finding cracks on i cant remember the name.

also throwing in the idea of the if it aint broke dont do anything logic

SpiderWeb · Sep 7, 2020

Many years ago the 211 club in seattle had some metal rings like piston rings but no gap. They were precision and for checking billiard balls.

Bavafongoul · Sep 7, 2020

I bought two sets of ball busters, one for myself and my best friend.

The gauge works really well & I’ve measured the hole for accuracy.

I also have electronic calipers & grams digital scale for testing weights.

Older pool balls tend to be a l’il lighter (grams) & a tiny bit worn (mm).

Two things that I’ve never found any issues with are roundness and roll.

Patrick Johnson · Sep 7, 2020

Bob Jewett said:
For those who think the diameters of a sphere tell the whole story, check out this video about a constant-diameter "sphere" that is clearly not round: https://www.youtube.com/watch?v=fOojOfpcPZM

Wow - that’s counterintuitive. Does constant width mean even weight distribution? Would that shape roll straight?

pj
chgo

Bob Jewett · Sep 8, 2020

Patrick Johnson said:
Wow - that’s counterintuitive. Does constant width mean even weight distribution? Would that shape roll straight?

pj
chgo

There is only one center of gravity. It is a variable distance from the strangely shaped surface. That means it will roll haltingly and/or with a wobble.

8cree · Sep 8, 2020

iusedtoberich said:
I'm working on a ball sphericity (roundness) tester for fun. Below are a couple of pictures, and a YouTube video link describing the process. I'll update as I go.

My motivation is to see how different ball sets and brands compare both when new, and when worn. Also because I like making things.

View attachment 556942

View attachment 556943

Youtube video with a lot more detail. Part 1:
https://youtu.be/fHgEgi62nO0

Very cool! Thanks for sharing

Bob Jewett said:
There is only one center of gravity. It is a variable distance from the strangely shaped surface. That means it will roll haltingly and/or with a wobble.

Yea, they are not replacing tires any time soon LOL

Designing and building ball roundness tester

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