My search came up with bupkus, but I spent some time weighing and measuring my Aramith balls today to determine the weight and diameter variance. It would be interesting to see more data on different types of balls. With so much marketing about the consistency of high-end balls, it would be interesting to see some data. I mention weight and diameter since those are trivial to measure. Clearly other factors such as the center of mass, roundness, surface all are important - but more difficult for the home gamer to measure.
Looking for Data on Balls
- Thread starter ryanshea
- Start date
Here is my contribution of precise measurements from a few years ago. Enjoy.
http://forums.azbilliards.com/showpost.php?p=4183444&postcount=13
http://forums.azbilliards.com/showpost.php?p=4183444&postcount=13
Interesting. Although you say you did not see a pattern from your set, clearly some balls were larger than others and they seem rather similar in out-of-round. I'm not sure why calipers are particularly bad -- I was able to get a repeatable measurement within a couple hundredths of a mm. The weight differences I think may be more significant though, especially comparing the average ball weight to the cue ball. My table is not so perfect the roundness seems good enough to not be the weakest link.
Va in the house.
267 called: it needs more money.
267 called: it needs more money.
FYI, I weighed a large sample of used balls in Valley bar boxes at my local pool hall. Here's an excerpt from Ball Weight and Size Difference Effects – Part I (BD, February, 2012), summarizing what I found:
To see how much ball weight can vary in typical conditions, I took an accurate digital scale to my local pool hall (“Match Ups” in Fort Collins, Colorado). I weighed the CB and randomly selected OBs (and the 1-ball specifically) in each of eight Valley bar boxes with the assistance and permission of the owners. (Thanks Mike and Nicole!) The CB weights were fairly consistent with an average of 5.89 oz (167 g), a minimum of 5.78 oz (164 g), and a maximum of 5.93 oz (168 g). The OB weights were lighter (2-3 percent on average) and less consistent with an average of 5.75 oz (163 g), a minimum of 5.47 oz (155 g) and a maximum of 5.89 oz (167 g). The lightest OB was a 1-ball, which makes sense based on the extra abuse it takes (but this could also just be coincidence). If the heaviest CB were paired up with the lightest OB, the percentage difference would be about 8%. Luckily, this is still much less than the 25% difference demonstrated with the pool and carom balls in HSV B.49. However, the weight-difference effects in this article would definitely be noticeable with this particular CB-OB combination, especially to a good and observant player.
And lots of info, articles, and a video relating to how ball weight and size differences affect play can be found on the ball weight, size, and wear effects resource page.
Enjoy,
Dave
Re pattern: That thread was originally about the balls being wider at the number than where there were no numbers. My data for one brand new set showed no pattern for this claim.
Re calipers vs micrometers, the main difference is in their construction. A caliper is a long beam, with cantilevered jaws. There can be much flexing/movement in the beam, jaw, or jaw to beam attachment. This affects the measurement. They are designed to measure large ranges, quickly, and with medium accuracy.
Micrometers by contrast, are very stout and heavy, use a screw to do the measurements, and the screw is inline with the measured object (not cantilevered).
Calipers are generally considered good for 0.002 to 0.003 inch [0.05 to 0.08 mm]. Micrometers are generally considered good for 0.0002 to 0.0005 inch [0.005 to 0.01 mm]
Dr. Dave's data is interesting, and I've noticed a smaller size for the low balls at my local pool hall in the decade+ old set, which is obvious simply by racking. Regarding micrometer vs caliper, I happen to have calipers which yield consistent enough results for what I wanted, but accurate results would be better, especially with multiple independent measurements.
What I was really after is not perfection, but basic data useful to a consumer. Larger sample sizes are great, but any sample is better than none. For those wanting to purchase a set of balls, today we can choose between marketing, folklore, and buying all ball types and measuring ourselves. Is there actually a difference in the consistency of material and tolerances on high-end balls?
Looking at how balls wear in real conditions is interesting, especially if similar vintage balls are compared between halls and the potential buyer is a room owner. For a home table the abuse pattern is going to be wildly different than a hall.
I don't mean to say that weight an size and roundness are the only, or even most significant factors. Resiliency also seems like a simple enough test to do with a tape measure, known hard surface, tripod, and the high speed video available on all our phones. I would guess that weight tolerance, resiliency, and how long a given material maintains its surface between polishing are the most obvious factors for a player.
What I was really after is not perfection, but basic data useful to a consumer. Larger sample sizes are great, but any sample is better than none. For those wanting to purchase a set of balls, today we can choose between marketing, folklore, and buying all ball types and measuring ourselves. Is there actually a difference in the consistency of material and tolerances on high-end balls?
Looking at how balls wear in real conditions is interesting, especially if similar vintage balls are compared between halls and the potential buyer is a room owner. For a home table the abuse pattern is going to be wildly different than a hall.
I don't mean to say that weight an size and roundness are the only, or even most significant factors. Resiliency also seems like a simple enough test to do with a tape measure, known hard surface, tripod, and the high speed video available on all our phones. I would guess that weight tolerance, resiliency, and how long a given material maintains its surface between polishing are the most obvious factors for a player.