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Old 02-23-2013, 03:42 PM   #51
Join Date: Jul 2008
Posts: 5,440

Originally Posted by JohnB View Post
I used two metal cycling cleats attached with strong, small width tape. So that the tape fits between the strings, around the frame. I moved both up and down by feel. I was worried if I put it to 10 and 2, the swingweight would be too high, but I might do that tomorrow, just to check whether it alters anything unexpected.
Nice McGyver action.

Could you, BTW, maybe explain to me what the reasoning is for wanting the upper part of head to be more powerful? I would say that in a normal groundstoke, the higher rackettipspeed would make up for that. Or is that also a matter of finding the right massgradiŽnt to even things out?
For high swingspeeds on rotational swings, yeah, the fact that the swingspeed is greatest at the tip and least at the throat ends up balancing out the fact that ACOR is greatest as the throat and least at the tip. Of course, spin is greatest near the tip because the racquet is moving fastest there, and least at the throat, so we might expect to find shots hit near the tip to land very short on topspin shots. But low ACOR (low hittingweight) also means a higher launch angle. So the shot hit near the tip will rebound at a higher angle and then the greater spin will bring it down to approximately the same depth on the court as the combination of greater ACOR, lower rebound angle, and less spin at the throat will.

But this is all most true for very high swingspeeds and low incoming ball speeds. So on serve you really don't lose much speed if you hit near the tip, if at all, and the extra spin is very welcome. But as the swingspeed slows down and the incoming ball speed increases, the low ACOR near the tip starts to penalize you. On a hard groundstroke, like 70mph shot speed, you might lose 2-4 mph if you hit 2 inches above the center with a traditionally weighted player's stick. And on a volley, where the incoming shot might be 70 mph or so, and your racquet is traveling only 15, things are worse. And made worse by the fact that volleys are relatively linear swings, so the tip isn't usually moving much faster than the throat, unlike with serves and rotational groundstrokes. So on a volley you might lose 5-7 mph on a shot struck near the tip compared to one struck in the center. Worse still, if we instead compare a volley struck 2" above center and one struck 2" below center we're looking at a possible difference of 15 MPH or so. And now the differences in launch angle and speed start to combine to produce shots landing several feet or more apart from each other on the court. So not only are you getting widely variable shot speeds at net but you're losing accuracy unless you can hit in the center of the strings each time, which you can't.

So this gradient business is mostly about volleys, but also could be important on groundstrokes if you're into equipment optimization or just generally geeking out on this stuff. And if you get the tip leaded up and ACOR improved up there you might be able to get a couple extra MPH on serve because most people tend to hit high in the hoop when serving. Stiff hoops also liven up the upper hoop, but doing it with mass is a more arm-friendly approach, (as long as your shoulder can handle the heft.) The poster Travlerajm introduced me to this topic, and if you're familiar with his experiments you'll know that he weights the hell out of the top of the hoop. He plays the net a lot so this probably really helps him achieve consistent power and accuracy up there. From that perspective it's pretty interesting. Sampras gained a lot by adding so much mass at 3&9, but I wonder if his volleys would have been even better had he put more mass higher in the hoop.

On the other hand, to my knowledge Edberg used a stock PS 85 without a bumper guard, which meant his swingweight was very low, with a steep ACOR dropoff near the tip. And he maybe had the best volleys of all time. So a strong case could definitely be made that we're here ridiculously overthinking this stuff.

All the "data" in the first couple paragraphs was generated with TWU's Shot Maker simulator. I've learned a lot from playing around with that thing.

Last edited by corners; 02-23-2013 at 03:45 PM.
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