One reason why you might be getting better control is the natural pivot length of the shaft might be better matched to your bridge length than a stiffer, higher-deflection (higher squirt) shaft. For more info, see:
Regards,
Dave
Break cue science
- Thread starter Bob Callahan
- Start date
Regards,
Dave
Obviously ... but "a very high speed of sound" makes no sense at all. Under any given set of circumstances the SOS will be constant.
LWW
I think his point was that the speed of sound in leather is different from the speed of sound in the other materials involved and that if you can find a tip material with a higher speed of sound, it may work better for his assumptions.
The speed of sound in wood is about twelve times the speed of sound in air. The CRC Handbook doesn't list leather.
The harder/denser a material is -- the faster the speed of sound (SOS) is in that material.
1. Given two break tips made of the same material, the harder one will have the highest SOS, and
2. Given two tips that measure the same hardness, the one made out of denser/heavier material one will have the highest SOS.
So the author seems to be saying that SOS is a better measure of goodness than hardness alone.
But, SOS ignores other important abilities -- for example, ability to retain chalk, weight, ...
Thanks for the comment. Dave, the new shaft is LD construction, so I expected to get the better control but I was surprised how much more power I could get.
I realize I'm making better contact but I ocassionally hit the stiff, high squirt shaft perfect and did not get the break action this shaft is giving me. Before this change , I would have said my break was below average compared to other players my level - now I would say it's not too bad when it's working.
I just assume that my old thick, heavy, stiff shaft was unsuitable for breaking.
Chris
,,, and probably the most important: the ability to give back the energy stored during compression. In an ideal contact, half of the speed of the cue ball comes from the decompression of the tip.
As Bob J. pointed out, the moment of inertia of the arm and hand about whatever point(s) they're rotating has to be taken into account. You can only generate so much force, and that has to move both the arm and the cue. A reasonable approximation over a relatively small arc is to treat the arm-hand as a non-rotating mass moving in a straight line (such as a shaft's "endmass" in squirt analysis). But this is extremely hard to determine directly. If it were zero, then 6oz would in fact be the ideal cue weight for a 6oz cueball. Given that experience over the years has "shown" that something on the order of 18-20 ounces is about optimum for cues in general, it works out that the equivalent mass of the hand-arm is roughly in that range. (It's not exactly a 1:1 ratio).
The ideal cue weight varies with tip offset. So if 18oz were optimal for a center ball hit with a particular player, at near maximum tip offset the ideal weight would be about 13 oz. But if you plug the numbers into the relevant formula, there really is virtually no difference in the results even if you're several ounces off the ideal...and not all that much difference even being 6oz off the optimum, as I remember it. (That agrees with your physics intuition - you mentioned earlier that you thought the curve would be relatively flat)
I think that even if you could directly measure the equivalent mass of a particular player's hand-arm, using a bit heavier break cue than recommended by the kinematics probably would be better. Our muscles can likely generate more maximum force due to the increased inertial resistance, but that's a question for biologists. I doubt that it matters a heck of a lot.
Jim
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I know nothing about physics. I do know that I break better with my 16 oz cues than with heavier cues. "Better" meaning more ball spread/action and better cb control.
Part of "better" is subjective as I have no means of measuring. My subjective bias is towards 16 oz cues. I like'm.
Part of "better" is subjective as I have no means of measuring. My subjective bias is towards 16 oz cues. I like'm.
I agree. In the absence of a kinematics lab, we can do a thought experiment.
Consider a plot of cue ball speed versus stick weight. Starting from a normal weight, as the stick mass is reduced, the speed will eventually fall to half "usual" speed (perhaps 10MPH vs. 20MPH for Joe Average). I'd guess that weight is around 8 ounces. At the high-weight end, I'd guess the stick will have to get up past 40 ounces before the speed gets back down to 10MPH.
In between, the speed-weight curve is unlikely to have a sharp peak; it is much more likely to look like a parabola or circle, maybe stretched on the high end. For such a curve, the range of weights over which the speed is 15MPH or more is about 70% of the range for 10MPH and greater than 17.5MPH is over a range of weights of ~50% of the 10MPH range.
Continuing the process for a reasonably smooth curve, we end up with ~97% or better of the peak speed over a range of 4 ounces of stick weight variation. At that point, I think comfort and what you have practiced with is a larger factor than stick weight for how fast the ball will be moving.
Bob -
Given that the speed of sound in maple is 4100 m/s, I'm wondering if break cue manufacturers are barking up the wrong tree going to harder and harder tips.
Presumably the motivation for going to hard tips--phenolic or whatever--is a belief that they are more efficient in the way you describe above.
Do you--or anybody--know whether this is true?
An unintended comsequence, though, of these hard tips may be that because the contact time is shorter, there may not be enough time for the ball to "see" the full mass of the stick.
4100 meters/sec is 4 meters per milsecond. A round trip for the compression wave is about 3 meters (two stick lengths). So it takes about three quarters of a milisecond for the cueball to even have a chance of knowing about the back of the stick.
My guess is the contact time for break tips is in that range.
Why not try an efficient soft tip? Maybe get the contact time up to 1.2 ms or more ?
What do you tink?
(Was this a pun on the sound of phenolic tips?)
I think it might be real interesting to engineer a ferrule that could do most of the energy storage in place of the tip. Maybe an actual spring.
Head racquets
Bob
Several years ago I ran across an R & D (DARSA?) concept of a liquid metal compounding where ball bearings bounced vertically for a LONG time before coming to rest. (sort of like a 'super ball') Is that a similar concept to the discussed energy storage and release upon decompression?
If memory serves-I think Head put out some tennis racquets and possibly some skis with this metal formulation.
Maybe a very thin walled ferrule of such material could work to store and release energy on a break cue? Sort of a solid spring--dunno.
Probably not/woulda been done already
Take care
Bob
Several years ago I ran across an R & D (DARSA?) concept of a liquid metal compounding where ball bearings bounced vertically for a LONG time before coming to rest. (sort of like a 'super ball') Is that a similar concept to the discussed energy storage and release upon decompression?
If memory serves-I think Head put out some tennis racquets and possibly some skis with this metal formulation.
Maybe a very thin walled ferrule of such material could work to store and release energy on a break cue? Sort of a solid spring--dunno.
Probably not/woulda been done already
Take care
Okay, so what I want to know... in plain english... is this:
When people say it varies from person to person, does it still "trend" towards light vs. heavy? Like maybe it's ideal at 16 oz for a fit 180 lb guy, 16.5 for a similarly built 200 lb guy, 17 for 220, 18 for 240, and so on?
IMO that trends towards "light".
Or are we saying it is so dependent on fast vs. slow twitch fibers that the 200 lb. guys might be ideal at 22 oz. while there's a bunch of 250 lb guys who are ideal at 17?
Is there a way to take the muscles of the breaker out of the equation and calculate strictly based on the stick? Like ...I know they have a pool robot out there. Somewhere. Was it Meucci who had it? What happens to the cue ball speed when you put a 17, 18, 19, 20, 21 and 22 oz in the hands of the robot, and just tell it to swing at the balls the same way each time? Does the speed of the CB get lower along a flat line as the stick gets heavier and heavier? Would a graph of the speeds show any sort of surprising curve? Is the whole thing irrelevant because fast. vs. slow twitch matters so much that a robot's results aren't valid?
When people say it varies from person to person, does it still "trend" towards light vs. heavy? Like maybe it's ideal at 16 oz for a fit 180 lb guy, 16.5 for a similarly built 200 lb guy, 17 for 220, 18 for 240, and so on?
IMO that trends towards "light".
Or are we saying it is so dependent on fast vs. slow twitch fibers that the 200 lb. guys might be ideal at 22 oz. while there's a bunch of 250 lb guys who are ideal at 17?
Is there a way to take the muscles of the breaker out of the equation and calculate strictly based on the stick? Like ...I know they have a pool robot out there. Somewhere. Was it Meucci who had it? What happens to the cue ball speed when you put a 17, 18, 19, 20, 21 and 22 oz in the hands of the robot, and just tell it to swing at the balls the same way each time? Does the speed of the CB get lower along a flat line as the stick gets heavier and heavier? Would a graph of the speeds show any sort of surprising curve? Is the whole thing irrelevant because fast. vs. slow twitch matters so much that a robot's results aren't valid?
The harder tips are more efficient. Bob and I actually did some measurement for this. Check it out:
Excellent point. My best measurements for phenolic tip contact time gave values close to 1/2 ms, but I didn't test at break speed. For more info, see:
Excellent points and questions. Anecdotally, it seems like the phenolic tips still provide an advantage over softer tips, which currently all seem to be less efficient.
Regards,
Dave
PS: TINK!!!
Using a robot..
I wouldn't think a robot would be particularly relevant in determining cue weights for breaking. The robot does not have the same muscle limitations that we do. Humans are more limited. The basic gist I get is that if you add an ounce to a cue, does the loss in speed (due to the inertia of a heavier object) offset the gain in mass and vice versa. I'm not a quick twitch guy. Im pretty big so I have better luck with heavier cues. Plus I struggle when I try to break "quick" rather than powerful. Like the Doctor says it depends on the person.
I wouldn't think a robot would be particularly relevant in determining cue weights for breaking. The robot does not have the same muscle limitations that we do. Humans are more limited. The basic gist I get is that if you add an ounce to a cue, does the loss in speed (due to the inertia of a heavier object) offset the gain in mass and vice versa. I'm not a quick twitch guy. Im pretty big so I have better luck with heavier cues. Plus I struggle when I try to break "quick" rather than powerful. Like the Doctor says it depends on the person.
Yes but what makes a GREAT break is all those things AND the best possible break cue for that person.
I don't think I can offer a satisfactory answer, other than that I agree that as the weight (mass) of whatever gets moving during the break stroke (e.g., hand, arm, body) increases, so would the optimum cue weight. If the typical choice of general playing cue weight (18oz - 20 oz or so) is based solely on what is a good match for their hand-arm mass (though no one of course does this explicitly) , then working backwards, you can figure out the typical hand-arm equivalent mass. From that, simple physics says that you should use a break cue of similar weight, or possibly a little heavier, in that you might be able to generate greater muscle force with a heavier cue. But the nagging question is, why have we come to feel comfortable with general playing cues in the range of weights we typically choose? Is it a good match to body mass, or are there other reasons?
I guess that's another complication.
I don't see how? As mr_griff indicated, the basic problem is this:
- The cueball responds to the momentum of the stick. Once the tip reaches the ball, a player's hand-arm mass has nothing to with it.
- A heavier cue has more momentum than a lighter one moving at the same speed.
- Given the same maximum accelerating force applied by the muscles, a heavier cue won't be going as fast when it reaches the cueball.
- The accelerating force supplied by the muscles has to propel both the stick and the hand-arm mass (and whatever else you get going). But once the tip reaches the ball, the hand-arm mass is dead weight and contributes nothing to the momentum the cueball reacts to (soft tissue coupling).
Putting that all together, you could figure the ideal weight IF you knew the other masses involved (hand-arm etc.) But therein lies the rub. You could try out sticks of different weights to determine that, indirectly, but then you've arrived at the end goal of the exercise without any need to know those numbers.
Frankly, as several posters have indicated, I don't think it's important. The math (though a simplification) suggests that you can be pretty far off the optimum weight and see little difference. Granted, I'm ignoring the fast/slow twitch aspect, but I can't see how a robotic substitute can offer an answer, or that you can look at the stick alone.
Jim
I think what cleared it all up for me just now is the idea that more weight = more momentum. For some reason, I had it in my head that a 26 ounce stick moving at 30 MPH will impart exactly the same amount of cue ball speed as a 13 ounce stick moving at 30 MPH. Therefore I was thinking lighter would pretty much always be better.
Now that I understand that the cue ball "knows" the weight of stick as well as its speed... I guess your goal is to find how much weight you personally can add for a given amount of breaking effort. You keep adding weight until the tradeoff between increased mass and decreased swing speed starts to work against you.
If there's a correlation between playing cue and break cue preference, what would be a good rule of thumb? I thought the hot new flavor in this thing was lighter sticks. So I would have thought playing cue weight minus 1 or 2 ounces. But Jim's suggesting +1 or so?
Wanna hazard a guess Dave?
Now that I understand that the cue ball "knows" the weight of stick as well as its speed... I guess your goal is to find how much weight you personally can add for a given amount of breaking effort. You keep adding weight until the tradeoff between increased mass and decreased swing speed starts to work against you.
If there's a correlation between playing cue and break cue preference, what would be a good rule of thumb? I thought the hot new flavor in this thing was lighter sticks. So I would have thought playing cue weight minus 1 or 2 ounces. But Jim's suggesting +1 or so?
Wanna hazard a guess Dave?
My best guess is:
It depends a lot on the individual.
Some people might do better with a heavier break cue (heavier by 1 oz, 2 oz, or more), and some might do better with a lighter break cue (lighter by 1 oz, 2 oz, or more). It's not just about physics ... anatomy (size and weight of arm parts) and physiology (slow twitch vs. fast twitch muscle fibers) are very important. The best way for an individual to find an answer is to try out and practice with various cue weights.
Regards,
Dave