Deflection question, explain how a stiffer CF shaft has less deflection.

[dr_dave]

the MORE the shaft deflects the LESS the cueball deflects.

… unless the end of the shaft close to the tip is heavy. For example, a very flexible shaft with a lead ferrule would create a shocking amount of CB deflection. See Diagram 4 in the following article showing the effects of mass added to the shaft at different distances from the tip:

Myth-Busting Experiments Dealing with CB Deflection​

 

[garczar]

… unless the end of the shaft close to the tip is heavy. For example a very flexible shaft with a lead ferrule would create a shocking amount of CB deflection. See Daigram 4 in the following article showing the effects of mass added to the shaft at different distances from the tip:

Myth-Busting Experiments Dealing with CB Deflection​

If the end was heavy it has too much mass regardless of flex and shaft wouldn't get out of the way quick enough so what i said still holds. I see what you're saying.

 

[slach]

According to Newton for every action there is an equal and opposite reaction. So if the cue flexes to the left X inches on impact a force of X inches to the right is applied to the cue ball. The more sideways flex in the cue the more opposite sideways force is applied to the cue ball. With a stiffer cue the force on the cue ball would be more forward, a flexier cue would impart more of a sideways force. And the amount of this force is determined by the mass of the cue's end. All other things being equal, more flex more deflection?? I'm no scientist, just some thoughts..

 

[Patrick Johnson]

Mount a "low deflection" shaft in linear bearings an inch or less from each end and it becomes low deflection no more.

Nice post, Hu, but I couldn’t translate this bit. WutchootalkinboutWillis?

pj
chgo

 

[dr_dave]

According to Newton for every action there is an equal and opposite reaction. So if the cue flexes to the left X inches on impact a force of X inches to the right is applied to the cue ball. The more sideways flex in the cue the more opposite sideways force is applied to the cue ball. With a stiffer cue the force on the cue ball would be more forward, a flexier cue would impart more of a sideways force. And the amount of this force is determined by the mass of the cue's end. All other things being equal, more flex more deflection?? I'm no scientist, just some thoughts..

See:

What Causes CB Deflection​

The shaft does not flex enough during the incredibly brief tip-contact time for shaft stiffness to have much effect. The shaft flexes the most after the CB is already gone (due to the sideways momentum of the shaft endmass).

 

[ShootingArts]

Nice post, Hu, but I couldn’t translate this bit. WutchootalkinboutWillis?

pj
chgo

Linear bearings force anything mounted in them, sometimes just one but always two, to have to move straight back and forth. With the shaft having no lateral movement to speak of mounted in those bearings and no flex to speak of mounted very near the ends the effective mass of the shaft would be, well, massive.

As you know an off center hit forces lateral movement in both objects, normally significant movement in both assuming similar weight and ability to move laterally. Lock one down and it's effective mass becomes huge, basically all the movement occurs in the other object.

Nothing tricky this morning!

Hu

 

[Patrick Johnson]

Linear bearings force anything mounted in them, sometimes just one but always two, to have to move straight back and forth. With the shaft having no lateral movement to speak of mounted in those bearings and no flex to speak of mounted very near the ends the effective mass of the shaft would be, well, massive.

As you know an off center hit forces lateral movement in both objects, normally significant movement in both assuming similar weight and ability to move laterally. Lock one down and it's effective mass becomes huge, basically all the movement occurs in the other object.

Nothing tricky this morning!

Hu

Thanks - what I figured.

pj
chgo

 

[Poolplaya9]

According to Newton for every action there is an equal and opposite reaction. So if the cue flexes to the left X inches on impact a force of X inches to the right is applied to the cue ball. The more sideways flex in the cue the more opposite sideways force is applied to the cue ball. With a stiffer cue the force on the cue ball would be more forward, a flexier cue would impart more of a sideways force. And the amount of this force is determined by the mass of the cue's end. All other things being equal, more flex more deflection?? I'm no scientist, just some thoughts..

If I'm not mistaken it seems like you may be thinking of this kind of like a diving board, where when a diver jumps up from the end of the diving board and comes back down it causes the board to bend down due to that downward force, but eventually the diving board reaches the bottom of its flex and then that flex reverses and the board starts springing back up and is able to impart much of that force back to the diver which ultimately launches them upwards. If that is along the lines of what you were thinking of, the key here is that the diver still has to be in contact with the board when it starts springing back up otherwise the diver wouldn't be there to receive that upwards launching force and it would never get imparted to them.

When it comes to the collision between a pool stick and a cue ball, while the stick does to some extent initially get bent away just like the diving board gets bent away, the part you may not have considered is that the cue ball is already long gone from the tip before the shaft ever has time to flex back against the cue ball. As a result the shaft is never able to impart that force/energy from being bent back into the cue ball the way the diving board has time to flex back and give its energy back to the diver and so the shaft flexibility doesn't matter much in this respect.

To further complicate things, the shaft doesn't even fully get bent/flexed away from the cue ball in the same way that the diving board is forced to have to get bent away from the diver. Rather than only bending to the side the way the diving board is forced to have to do, in large part the whole shaft is actually getting pushed to the side rather than just having to get bent to the side because the whole bridge hand is able to move to the side some, and because the skin and muscles of your bridge hand have a lot of play in them which allows the stick to push into them instead of having to bend, etc. There is just a lot of flexibility there that allows for the shaft to largely get pushed to the side instead of having to only get bent to the side and so it doesn't have near the stored energy it would if it all had to go into bending the shaft the way it all has to go into bending the diving board. In any case though, whatever energy is able to get put into bending the shaft sideways is never able to get imparted back into the cue ball from the shaft flexing back because unlike with the diving board and diver the cue ball is long gone before the shaft has time to spring back against it.