Originally Posted by spaceman_spiff
Thanks for the follow-up. I didn't see the original paper, so I didn't know if the 100 g was a specific amount for a specific frame or just intentional overkill guaranteed to cause reversal in any racket (like saying a 5-lb brick will squash any grape).
The more I think about the problem, the more I suspect that what you're really looking for is a particular distribution of mass in terms of the ratio of mass in the upper, middle, and lower hoop. That is, if you have a frame with x% of the mass in the upper third of the hoop, y% in the middle third, and z% in the lower third, you'll get that consistent spin potential across the whole string bed regardless of the overall specs.
The difficult part is finding the exact values for x, y, and z, which will probably vary a bit frame by frame given differences in head shapes, flex patterns, and string spacing. If I were in your shoes, I'd start with the Exo3 Red and see if that 60 g really does give you the consistent spin potential that you're looking for (forget overall specs and personal preferences for the moment). You might find that that necessary modifications are more complicated and the results are difficult to verify.
But, if you do end up finding a way to verify the results and get what you're looking for, then you can start searching for other frames that will give you the overall specs you like after you've modified them to get that consistent string bed.
Basically, test the feasibility first on a well-known subject and then start looking for more ideal candidates later.
Thanks. But I think the issue here is not the distribution of mass from the top to the middle to the bottom of the stringbed. Trying to create a power gradient from top to bottom is a worthy goal because in theory it should be possible to setup a racquet so that a shot struck near the throat, a shot struck near the center and shot struck near the tip all rebound at the same speed. This would definitely improve control, because with stock racquets there is significant variation in shot speeds rebounding from different locations.
But I think it's pretty clear from the paper that two effects dominate the observed difference in spin generation between high (toward the sky) and low (toward the ground) impacts: the rotation effect and the short-side effect. If hittingweight, or the hittingweight gradient from throat to tip, were the critical factor, then the 100 grams added at 11&1 should have reversed this gradient, as 100 grams added to those locations would have bumped the swingweight by about 250 units. Adding 100 grams at 3&9 "only" increases swingweight by 200 units. But the relationship is reversed in terms of twistweight. Those grams at 3&9 increase the twistweight by about 12 units, while adding at 1&11 would only increase it by about 7 units. I think it's pretty clear that the reason why mass added at 3&9 worked to reverse the spin difference is because of the twistweight increase, which makes sense if you carefully read the descriptions of the rotation and short-side effects. Looking at the experimental results, it appears that adding mass at 11&1 would work too, but you'd have to add even more mass, like maybe 150 grams, which takes me far away from the secondary goal of keeping swingweight at a swingable level.
This is why I don't think it matters which frame I start with, as long as it has a twistweight of 11 or more, stock. Increasing swingweight, and thereby increasing hittingweight, should increase spin at all impact locations, but shouldn't change the observed spin gradient that much, if at all. So I'm not too concerned about the stock or final swingweight. (I might be wrong about this, however.)
In addition, the experiments in the paper provide a basis for further experimentation. It would have been best if the TW Professor had tried 60 grams and confirmed his hunch; but, his results with 100 grams certainly light the way towards trying 60 grams at home. Going in another direction entirely would, in my opinion, require a controlled spin testing rig like he has, which I haven't got. So I'll restrict my wild racquet ramblings to the path already slightly tamped down.
Unfortunately, all that mass concentrated at 3&9 will not equalize the throat to tip power gradient. But that's another problem, and one that Travlerjam has solved, I believe, by concentrating mass in the entire top half of the hoop, from 3 all the way round to 9. This is what Head has done too with their new Graphene Speed Pro, at least that's what their marketing says.