How did you get such a conclusion? Adding mass at various distances is a completely different physical model than bridging with a hand at different lengths.
[...]
A few reasons for my conclusion:
1) The way mass is added is not in question, just the fact that it is added. It could be through a clip, a lead weight, bubble wrap, or, in this instance, your bridge. For example, if a closed bridge "slid" with the cue at a specific distance (say 4" from the tip), rather than the cue sliding through the bridge, there would be an effect end mass change, albeit a difficult one to measure since the entire weight of your bridge would not be effectively added to the shaft. But an addition nonetheless. Even taking into consideration the "give" properties of skin, there is some weight added by your fingers (i.e., resting on the cue (explained a little more below)).
2) The timing of the addition of the weight is not an issue. The .3 or 1.1 g Dr. Dave used could be added at any time before contact and still yield increased squirt. Thus, a cue is sliding through a bridge would be an equivalent system to adding "end" weight during, or towards the end of, the stroking process. Where your hand is and the time of contact (i.e., distance from the cue ball) will dictate how much the endmass will change.
[NB Based on Dr. Dave's results, extrapolating to a .1 g increase in effective endmass results in something like a 0.5 degree change in squirt at a distance 3 distance from the tip, and .25 degrees at 4 inches. I'm sure this could be calculated to a greater degree of error, but for the sake of my conclusion, I noted that .1 g is not very much weight, and .5 degree change in squirt (which results in about a .75" in horizontal distance over a 7 foot distance - which about 1/3 of a cue ball), and .25 degrees yields about .37"]
3a) In order for the bridge
not to matter, it would have to be (a) greater than 7" away from the tip, or (b) result in
no change in endmass at all. I have tried to contemplate different ways for (b) to occur, and the best I could come up with was an open bridge.
3b) Taking myself farther along this rosy path: I assumed a finger weighed 1.1 g (since it was a convenient number
). If you have a closed bridge, even a loose one, there is some part of your finger, skin, knuckle, something resting on the cue at impact. If this weight happens to be .3g, you would get the results show in Fig. 4. And even at .1 g, it would have some effect as I noted above. The tighter your bridge, the more weight of you finger is applied to the cue. Along with this is the likelihood that (at least some percentage of) the entire weight of your hand will be applied to the cue as well. If your bridge was tight enough, you would end up with a physical approximation of Mike's vice grip experiment (with the total added weight (potentially) being your entire hand).
Thus, it appears (at least to me) that bridging would, in fact, affect end mass - either by creating more endmass, or by not doing so (i.e., an open bridge). And the closer the bridge to the tip, the greater the effect of even a small addition of weight. Specifically, the good Drs. results show that at up to about 4.5" a very minimal addition of mass will result in measurable squirt variance, and at 2", the results are dramatic.
Are there any specific reasons why you think a bridge, or even a finger resting on the cue, would have zero effect on end mass? Maybe I'm missing something.
IMO, it's the bridge length *and* the materials used by the Myth Destroyer that makes its result unrealistic. The material (bridge and grip) is too stiff, much stiffer than a hand could ever be. The combination falsely adds mass to the collision, IMO.
Bridge length past 7" is irrelevant (as Dr. Dave showed). The "rigidness" of the bridge (i.e, too stiff) results in something like Mike's vice grip experiment. And although the results are clearly an extreme (super tight grip and a questionable distance), they illustrate that a bridge does in fact add end mass.
-td
