- Dec 25, 2010
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great stuff pobguy!
Topspin Vs Bulletspin, Which is Faster?
- Thread starter ArmWhip
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CORRECTION: I had earlier said 75 rps was about the spin needed for the ball to rise above its initial plane, assuming 70 mph release speed. I messed up (yes, even physicists do that, more often than you think; but, we are very good at finding our mistakes). It is more like 60 rps, still about twice what RevFire gives for elite players. The numbers for the spin in the slides I posted earlier are not my own numbers. The PITCHf/x system does not measure the spin. It measures the movement and used that to infer the spin, with the aid of a model. I don't recall offhand whether the model that is used is the best one available, so the absolute numbers for spin should be taken with a grain of salt. The numbers for movement are much more reliable.
The rev fire numbers posted by ffs say an "average" rps is 17-20... how on earth could anyone ever get near the 75 mark?
When DD's old PC used the rev fire and she was averaging about 18 with and occasional 19 or 20, he acted as though she was performing great! So when someone suggests a 75 is a target number, I was really confused!
When DD's old PC used the rev fire and she was averaging about 18 with and occasional 19 or 20, he acted as though she was performing great! So when someone suggests a 75 is a target number, I was really confused!
Perhaps you misunderstood. I posted that number in response to a question of how rapidly the ball would have to be spinning to cause the ball to rise above the plane of its initial trajectory. The answer, 60 rps (I downgraded from 75), is the approximate spin rate It is definitely not something anyone should aim for, since it is humanly impossible (as you point out). And BTW, what does DD mean? Are you referring to a particular person?
FiveFrameSwing
Banned
I've seen girls increase their spin beyond that stated in the table ... and unfortunately loose significant speed in their journey to increase spin. Leads me to wonder if high spin rates really should be a goal.
Our broken CF4 in the garage, DD means
DiMarini Destroyer
I am curious about how the speed of a pitch affects it's break. In several posts here people have said that as a pitch slows down it breaks more (curves not rises), this is used as an explanation of 'late break'. As a curveball slows down will it break more? Also, I have always thought that more velocity meant more break. Given equal spin rates will a faster pitch break more or less than a slower pitch?
Both excellent questions. Let me take the 2nd question first. The strength of the Magnus force that causes the break is approximately proportional to the product of the spin rate and the speed. So, the force is larger (for a given spin rate) if the speed is larger. However, the time over which the force acts is inversely proportional to the speed. Moreover, the total break depends on the square of the time. So, putting all this together, for a given spin rate the amount of break is inversely proportional to the speed. More speed means less break.
Now the first question is easier to answer. As the ball slows down, there will be more break. However, the ball does not slow down enough to see that effect. The data from MLB are consistent with a constant Magnus force over the full trajectory of the pitch. So, that effect will not lead to "late break". If the path of the ball were longer, you would definitely see the effect. In fact, you can see the effect on a long spinning free kick in soccer. The physics is all the same, but over the long path of the kick the ball loses sufficient speed that you can see the increased break.
I will be writing an article in the coming weeks for the on-line baseball publication Baseball Prospectus. The topic will be my analysis of the 2011 WCWS data. I'll address many of these points in the article. I'll let everyone know when it is up.
Greenmonsters
Wannabe Duck Boat Owner
Dr. N - Don't know if you've seen the clip of Fraizer's "no hands" home run. There's another thread going on where hand position/grip strength AT point of contact is being discussed (http://www.discussfastpitch.com/softball-hitting-practical/18090-hand-action-contact.html ). It would be appreciated if you would kindly share some insight on this!
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