Originally Posted by corners
Rod Cross has been modeling tennis strokes, including the serve, as double pendulums for several years, with two papers appearing in the past twelve months.
I have read his A double pendulum model of tennis strokes
in American Association of Physics Teachers. I can find nothing there that even remotely support the use of MgR/I. He is studying a double pendulum with an applied force and without gravity (see fig 1 and the appendix) which have a very different behavior.
Any other sources?
This isn't the case. Many racquets on the market are reasonably close to 21.0, especially traditional players' frames like the Pro Staff 6.0 and the Prestiges. I support your skepticism but I think you're misinterpreting this notion of MgR/I and its use. It's not meant as a stand-alone, be all/end all.
If the ratio doesn't make some sense to you after these experiments then we can confidently add your report to the "MgR/I is rubbish." pile of anecdotes.
Say you have two parameters A=10 and B=5
1. If you say that A=10 and B=5, then saying that A/B = 2 doesn't ad any information, it follows automatically.
2. If you say that B = 5 and A/B = 2, it is the same as in 1. just a slightly more complicated way of saying that A=10 and B=5
3. If you only say that A/B = 2 then you have solutions like A = 5 800 and B = 2 400
You admit that 3. is not sufficient and you have to set B as well. If you want to describe your relation as 2. fine, as long as you are aware that it is the same as 1.
So I don't doubt that your customization work. But it does so because you set the fundamental properties, not the relation.