Flex Point Question

[Cornerman]

I'm not a cuemaker, but I'm a mechanical engineer. I'm sure I know what a flex point is on a beam, though it would be a misnomer.

Someone's already put the definition that would be consistent in structural engineering: the point of highest instantaneous rate of change of beam deflection in a given end-loaded condition (assuming a supported opposite end).

This beam deflection profile has nothing (statistically insignificant) to do with cueball squirt and shaft pivot points. Proven over and over and over and over, but I know there is still confusion in the cuemaker community.

If anyone wants a real discussion on this, get a hold of me. I won't exhaust myself here again.

 

[PoppaSaun]

I'm not a cuemaker, but I'm a mechanical engineer. I'm sure I know what a flex point is on a beam, though it would be a misnomer.

Someone's already put the definition that would be consistent in structural engineering: the point of highest instantaneous rate of change of beam deflection in a given end-loaded condition (assuming a supported opposite end).

This beam deflection profile has nothing (statistically insignificant) to do with cueball squirt and shaft pivot points. Proven over and over and over and over, but I know there is still confusion in the cuemaker community.

If anyone wants a real discussion on this, get a hold of me. I won't exhaust myself here again.

I don't think they were necessarily asking about squirt or pivot points, rather about 'feel'. The deflection profile of the shaft likely has a lot to do with that.

 

[Cornerman]

I don't think they were necessarily asking about squirt or pivot points, rather about 'feel'. The deflection profile of the shaft likely has a lot to do with that.

Maybe I misread. Thanks.

 

[JoeyInCali]

I'm not a cuemaker, but I'm a mechanical engineer. I'm sure I know what a flex point is on a beam, though it would be a misnomer.

Someone's already put the definition that would be consistent in structural engineering: the point of highest instantaneous rate of change of beam deflection in a given end-loaded condition (assuming a supported opposite end).

This beam deflection profile has nothing (statistically insignificant) to do with cueball squirt and shaft pivot points. Proven over and over and over and over, but I know there is still confusion in the cuemaker community.

If anyone wants a real discussion on this, get a hold of me. I won't exhaust myself here again.

That being the end-mass is the only thing that matters in squirt ?

 

[Cornerman]

That being the end-mass is the only thing that matters in squirt ?

As I said, I won't exhaust myself on here.

End mass is NOT the only thing that matters in squirt, and we (the collective we) have said this multitudes of times.

Freddie <~~~ exhausted already

 

[qbilder]

Bump a shaft & watch it vibrate. You'll see exactly where the flex point sits. It's technical term is nodal, basically meaning that it's the point that stays relatively the same while everything else moves. In a guitar it's the spot(s) along the string that stay relatively still as the string vibrates. In a shaft it's the spot where the wood flexes away from. Every cue I have made in the last 15 years has a flex point 11.5" from the tip, and another about the same distance opposite the joint, near the handle. Just like a guitar string can be tuned by manipulating the nodals, so too can a cue.

 

[Cornerman]

Bump a shaft & watch it vibrate. You'll see exactly where the flex point sits. It's technical term is nodal, basically meaning that it's the point that stays relatively the same while everything else moves. In a guitar it's the spot(s) along the string that stay relatively still as the string vibrates. In a shaft it's the spot where the wood flexes away from. Every cue I have made in the last 15 years has a flex point 11.5" from the tip, and another about the same distance opposite the joint, near the handle. Just like a guitar string can be tuned by manipulating the nodals, so too can a cue.

Now we're talking !!! From a dynamic, acoustic, and vibration standpoint, I would guess that what cuemakers want for this misnomer of "flex point" are the nodal points.

Add the tone of the material and you've got to enough metrics to properly describe the hit of a cue at least in order to compare from one cue to another. The nodal points and tones maybe won't mean a thing to most players, but maybe in the future it will!

Freddie <~~~ I like it!

 

[HawaiianEye]

Bump a shaft & watch it vibrate. You'll see exactly where the flex point sits. It's technical term is nodal, basically meaning that it's the point that stays relatively the same while everything else moves. In a guitar it's the spot(s) along the string that stay relatively still as the string vibrates. In a shaft it's the spot where the wood flexes away from. Every cue I have made in the last 15 years has a flex point 11.5" from the tip, and another about the same distance opposite the joint, near the handle. Just like a guitar string can be tuned by manipulating the nodals, so too can a cue.

Eric, thank you for your info.

How have you controlled the "nodals" to be as exact as they are on your cues?

Is it the taper, the wood selection? Magic?

 

[qbilder]

Now we're talking !!! From a dynamic, acoustic, and vibration standpoint, I would guess that what cuemakers want for this misnomer of "flex point" are the nodal points.

Add the tone of the material and you've got to enough metrics to properly describe the hit of a cue at least in order to compare from one cue to another. The nodal points and tones maybe won't mean a thing to most players, but maybe in the future it will!

Freddie <~~~ I like it!

This is the stuff my cue making revolves around. Yes, flex point is exactly how I describe the nodal points in my cues. Before I knew anything concrete about deflection, the front node was an attempt at controlling deflection. I wasn't trying to rid it, but rather keep it within certain parameters so to attain a higher level of consistency from one cue to another. I believed the cue would flex most at that spot, preventing erratic deflection and spin. Now I am aware of many things I missed regarding deflection, but i still believe in the notion behind the flex point. If anything, it has caused me to give serious consideration to the relationship between deflection and flex points. Although completely different phenomenon, their paths do cross.

 

[qbilder]

Eric, thank you for your info.

How have you controlled the "nodals" to be as exact as they are on your cues?

Is it the taper, the wood selection? Magic?

On my cues, it's the taper shape. Wood selection doesn't matter much because the dimensional shape dictates where the node will be. May be a different story on long sweeping progressive tapers, though. Wood selection does matter in the butt, however, which is where the rear node is located. I find that it moves forward or back depending on how stiff/rigid the butt is. Doesn't matter much to me tho because I haven't noticed any correlation between the rear node & how the cue hits.

 

[conetip]

Bump a shaft & watch it vibrate. You'll see exactly where the flex point sits. It's technical term is nodal, basically meaning that it's the point that stays relatively the same while everything else moves. In a guitar it's the spot(s) along the string that stay relatively still as the string vibrates. In a shaft it's the spot where the wood flexes away from. Every cue I have made in the last 15 years has a flex point 11.5" from the tip, and another about the same distance opposite the joint, near the handle. Just like a guitar string can be tuned by manipulating the nodals, so too can a cue.

This is very true. But with composites, it is now possible to make the shaft not have a fixed nodal point, but a moving nodal point. It is also called self dampening. Not easy to achieve, but is achievable with materials available for the last 4 years. I have no idea if it can be achieved in a wood cue shaft though.
Neil

 

[JoeyInCali]

Pred and Meucci owners aren't going to like the tap test.

 

[Cornerman]

This is very true. But with composites, it is now possible to make the shaft not have a fixed nodal point, but a moving nodal point. It is also called self dampening. Not easy to achieve, but is achievable with materials available for the last 4 years. I have no idea if it can be achieved in a wood cue shaft though.
Neil

If nothing existed 20 years ago, and you posed this, I would have said:

I'm quite sure using piezo technology that a self-dampening system can be made.

Freddie

 

[qbilder]

What would self dampening do for the hit, and how well would the material reflex back to original shape?

 

[Cornerman]

What would self dampening do for the hit, and how well would the material reflex back to original shape?

It would just reduce vibration amplitude so that the feel would be muted.

 

[louieatienza]

Bump a shaft & watch it vibrate. You'll see exactly where the flex point sits. It's technical term is nodal, basically meaning that it's the point that stays relatively the same while everything else moves. In a guitar it's the spot(s) along the string that stay relatively still as the string vibrates. In a shaft it's the spot where the wood flexes away from. Every cue I have made in the last 15 years has a flex point 11.5" from the tip, and another about the same distance opposite the joint, near the handle. Just like a guitar string can be tuned by manipulating the nodals, so too can a cue.

In the acoustic guitar (and violin) world, some of the more scientifically and methodically minded builders will use a tone generator with a speaker to "excite" the soundboard, which would have been sprinkled with something like glitter, sand, or sawdust, which would create "Chladni" patterns - the particles will gather and form lines where the nodes are on the particular soundboard. The goal is to create a circular node, which in theory allows the freest movement of the soundboard. This is done by selectively shaving the braces and thinning the soundboard (or even adding mass in some parts). Having this particular node at a low frequency is thought of to bring out more "bass" to the guitar's voice, which for the steel string guitar naturally tends naturally toward the treble.

It would be impossible of course to do this with a cue, but a cue could be set on two points somewhere close to where the nodes are, and "excite" the cue by clamping something to one end that can vibrate at the frequency of the cue - a mini version of Tesla's earthquake machine. It could even be a small servo with an eccentric weight that can be set at an exact RPM. Slow motion video (maybe with a GoPro) would illustrate the two (maybe more?) nodes... probably before it destroys the cue!

While I do not look for a particular "node" on a cue I play, I actually do hold a cue with my right hand where I normally grip, and "bump" the cue near where the joint area is and observe how the tip end of the shaft vibrates, and how it feels on my right hand. By no means scientific, but I prefer to see that tip vibrating faster, which indicates to me the cue will play more on the stiff side, and the vibrations sustain a bit but not too long (compared to another cue), clueing me in that the "hit" will feel crisper without being harsh, for lack of better word.

 

[conetip]

If nothing existed 20 years ago, and you posed this, I would have said:

I'm quite sure using piezo technology that a self-dampening system can be made.

Freddie

Now it can be done without piezo technology. It is actually an unintended but welcomed side effect of some new weave geometry in the cloth itself.
Quite fascinating I think.
Neil

 

[Cornerman]

Now it can be done without piezo technology. It is actually an unintended but welcomed side effect of some new weave geometry in the cloth itself.
Quite fascinating I think.
Neil

Very fascinating!

 

[louieatienza]

Another cool idea would be to weave electroactive polymers in with the CF, where the shaft can react almost instantaneously, based on a microprocessor in the butt. The shaft could also then be programmed for damping, (or evwn amplification), stiffness, bend profile... with presets saved and programmed via smartphone...

 

[scdiveteam]

Hi,

IMHO the best playing shaft taper geometry is 13MM or a tad thicker and will flex at about 7 to 8" from the tip if you hold them on the ends and flex the shaft.

Rick