cue tip

Dr. Dave's answers to frequently-asked questions (FAQs),
mostly from the BD CCB and AZB discussion forums

maintained for the book: The Illustrated Principles of Pool and Billiards,
the DVD series: The Video Encyclopedia of Pool Shots,
and the monthly Billiards Digest "Illustrated Principles" instructional articles

deformation and mushrooming
contact time
hardness and English
recommended brands
size

deformation and mushrooming

How much does the tip deform during contact with the cue ball?

Here's an image from some high-speed video filmed by a group from Austria a couple of years ago:

The full video clip can be viewed at HSV A.76 (it is the third clip in the sequence). The video was shot at 2000 frames per sec with a high-resolution color camera. Here's an isolated clip of the close-up of the tip contact:

I've collected a sequence of images from the video clip and have made them available in MS Word and PDF formats. The MS Word file is large (1.7 MB), but it is very useful. If you page down through the file to load all of the images, you can then use the scroll bar to simulate a flip-book animation. The faster you scroll, the faster the simulated "video" plays. The images are 1/2000 second (0.0005 or 5 ten-thousandths of a second) apart.

Here are some observations, insights, and questions from the collection of stills:

- The tip is probably relatively soft based on the contact time and amount of deformation. Contact lasts about 4 frames (over frames 3-6), which corresponds to about two thousandths (0.002) of a second.

- The cue tip seems to stay in contact with the ball as the ball starts to rotate, which might contribute to the amount of cue stick deflection.

- The cue tip had an excessive amount of chalk on it (as evidenced by the pre-impact chalk trail through the air and by the huge chalk cloud after impact).

Is it important to remove the mushroomed edges of a tip?

If your tip is properly shaped tip and you are hitting the cueball within the non-miscue zone, the extreme edge of the tip doesn't come into play (e.g., see the diagrams in my July '06 instructional article dealing with "tips" of English).

However, removing the mushroomed edges does:

make the tip look prettier, and it might be less visually distracting to some.
feel better if you happen to pull the tip back through your bridge during your stroke (which isn't recommended).

contact time

How long is the tip in contact with the cue ball?

Clips HSV A.77-A.81 and A.147-A.151 show close-ups of cue tip impact for various hardness tips and various speeds. Here are some conclusions:

most contact times (i.e., for most tips and most speeds) are very close to a thousandth of a second (0.001 sec).
a soft tip at slow speed has a longer contact time (about 0.002 sec), but still extremely small.
a very hard tip (phenolic) at fast speed has a shorter contact time (about 0.0005 sec).
the contact time decreases slightly for faster speeds, but not by much.
chalk does not stay on hard tips very well at impact (see the blue clouds that separate from the tips in the videos).

hardness and English

Does the tip hardness affect how much Enlgish can be applied?

Here are some relevant factors:

A hard tip holds its shape better over time, in general.
Tip hardness should not have a significant or direct effect on the amount of English that can be applied.
The amount of English is limited by the tip offset that creates a miscue.
A tip not "treated" (e.g., scuffed) properly, will not hold chalk very well, and miscues will be more likely at smaller tip offsets. A harder tip might require more attention in this regard.
Soft tips seem to hold chalk better than hard tips, in general.
A soft tip will give the cue a softer "feel" (less impact in grip hand) and have a different sound than a hard tip. Some people prefer some sounds and "feels" other others.

For the effects of tip hardness on squirt, see my August '08 article.

Some people think that because a soft tip stays in contact with the CB slightly longer (see contact time), a soft tip can apply more English. However, see Bob_Jewett's comments below. Also, the contact time is still extremely small with both a soft and hard tip: close to a thousandth of a second (0.001 sec). Assuming the CB speed is the same in all comparisons: even though the peak force will be different (more with the shorter contact time), the amount of momentum (linear and angular) transferred to the CB will still be the same (because the sum of force over contact time is the same in both cases). The CB doesn't move much (translation or spin) during the extremely small contact time, so the only significant factor is the tip contact point at impact.

On a different note, a hard tip will create slightly more CB speed for a given cue speed (see HSV B.42 - tip and cue efficiency, with Bob Jewett). Some people also prefer a hard tip because they "feel" the force of the shot better (a softer dip dampens the impact a little).

from Mike Page:

Here's one more. Even if soft and hard tips held chalk exactly the same, it's possible the soft tip might reduce the chance of miscue. For instance, suppose a miscue occurs when less than 50% of the contact patch has chalk. If the bald regions are small, then this standard may be violated more frequently for a hard tip with its small contact patch.

from Bob Jewett:

One issue is which harness of tip will allow the farther-from-center hit. Some believe that a soft tip takes chalk better so it can hit the ball farther from center.

There is a counter theory, and that is because a softer tip will have a longer contact time than a hard tip. During contact, the tip rides around the side of the ball some, so the final eccentricity as the tip leaves the ball is larger than when the tip first hits the ball. A softer tip, with the longer contact time will be farther off center at the end than a harder tip with the same starting offset. If both tips can only hold to a certain point of offset, and you start your shot so the miscue point is barely reached at the end of contact, the average offset will be larger for the harder tip. This means that the harder tip can create more spin for a given ball speed.

Which dominates? Holding chalk better or starting farther off-center? I don't know of any experiment that has tested this.

How hard are some tip brands relative to others?

See: http://www.poolndarts.com/71-Tips/ and http://www.poolcuenews.com/2008/02/20/damn-my-tip-is-hard/

recommended brands

What brands of tip are commonly recommended?

Morri, Sniper, and Triangle.

size

Does the tip and shaft size make a difference?

For applying English, a smaller and rounder tip (approximately dime radius) is generally recommended. Here are some possible reasons:

The smaller, rounder shape allows for a more uniform contact area as the tip offset is increased. If you have a copy of my book, this is illustrated in Figure 2.2 on pg. 18. This could help make miscues less likely at large tip offsets.
A smaller tip and shaft will have less endmass and squirt. There are possible advantages and disadvantages with a lower-squirt shaft.
A smaller tip might make it easier for some people to visualize and pinpoint the desired tip contact point on the cue ball.
With large tip-offset draw shots, you get more table clearance (see my July '06 article for illustrations) with a smaller and rounder tip.
For shots with English, the impact is more centralized to the core of the cue for a smaller, rounder tip. This might result in a better "feel" for some people with firm shots. Also, some people, for example Predator, claim the centralized hit helps reduce squirt. I'm not sure about this, but I have no evidence to suggest otherwise. It certainly is true that if you remove more tip material by rounding it down to a dime, you will reduce endmass and squirt.

One advantage of a larger, flatter tip is that a center-ball hit, with some tip placement inaccuracy, will generally have less unintentional English (and unexpected throw). In other words, a larger, flatter tip is more "forgiving" with near-center-ball hits.

Another concern related to shaft diameter is bridge comfort. With a closed bridge, some shaft sizes and tapers will be more comfortable than others to different individuals. This is less of a concern with an open bridge.

The shaft size can also influence how some people apply English, if they use "tips" of English and/or an aim-and-pivot squirt compensation system (e.g., BHE). This might make some people think they are getting more or less English with different size and shape tips. For more info, see my January '08 BD article.