Yes, it would make sense that stronger people would use heavier bats, because they would have a higher maximum swing rate. I have found that I can’t swing a 23 ounce bat any faster than I can a 28-29 ounce bat. So for me, a 28 ounce bat gives me the most power. If McGwire can swing a 34 ounce bat at his maximum arm speed, then he would create the most power with that weight. It’s hard to compare Ruth, because the technology behind the bats was so different, as well as the balls. Also, some bats have thick handles, different lengths, etc. All these factors would also make a difference.
I think it gets even more complicated than that. A lighter bat will transfer more energy back into the batter’s arm, where it will be absorbed by the muscles. There may be some impedance issues here too. Finally, shock waves from the impact may travel up and down the bat, and the resonant frequency of the bat may change how much energy is imparted back into the ball.
Robert Byrne did some experiments with billiard cues, to see whether lighter cues worked better than heavier ones. He took the end rail off of a pool table, then he and some friends who were all professional pool players started shooting cue balls off the end of the table with different cues, and measuring their impact points on the floor to calculate velocity. The conventional wisdom was that a heavier cue would provide more power, but they found that almost all of them could hit the cue ball farther with a 19oz cue than with a 21oz cue.
That might be a case of apples and oranges. With a bat, you have rotational force, and almost no compression at the hitting surface. A pool cue is pretty soft, and is struck no where near as hard as a baseball bat. And it is a linear motion.
You may be right, but it also suggests that the issue is more complex than a simple mass/velocity relationship. Another thing they tried was putting tips of differing hardness on the cue. First, a cue with no tip at all was tried, and didn’t work very well at all. Then a very spongy tip was used, and didn’t work all that well. A hard leather tip provided the best results. So there are some transfer of energy issues here as well.
Getting back to bats… When you hit the ball, a shock wave might travel up and down the bat. If the ball is still in contact with the bat when the shock wave comes back, the energy would be transferred to the ball. If not, the energy would be lost as vibration. The wrist and arm would also absorb some of the collision energy, and that amount would differ with different shapes and sizes and weights of bat.
Yeah, and another thing is that you may use a 34 ounce bat, and I use a 32, but my bat has more weight in the hitting zone. Yours could have a thicker handle, and I could have the cupped out end on my bat too. Also, different lengths of bats matter, since the longer the bat the greater the speed at the end. Speaking from experience, I hit with the most power using the heaviest bat that I can swing as fast as my arms will allow. Right now, that is a 28 ounce 33 inch long bat with a 2 3/4 inch barrel. It’s a composite aluminum alloy.
I’m gonna throw this in here too. I have a baseball game today at 2:00. Now last week, the temp was 92 outside, but 125 on the field. It is supposed to be 98 today. I don’t want to go. 
dhanson
Member posted 07-30-99 02:40 AM
"Getting back to bats… When you hit the ball, a shock wave might travel up and down the bat. If the ball is still in contact with the bat when the shock wave comes back, the energy would be transferred to the ball. If not, the energy would be lost as vibration. "
I read somewhere that the point where the shock waves reinforce is what's called the "sweet spot". Is that true?
As for the central question of what's the best bat: it seems to me that as far the initial impulse is concerned, the ** mass** of the bat is irrelevant; what matters is the ** inertial moment **, which is basically a measure of how much mass is how far away from the batter (in the rest of my post, "light" and "heavy" shall refer to m.i.). The mass in the handle does very little, while the mass at the end of the bat does a lot.
In the first part of the swing, the impulse should be proportional to the velocity of the bat times MI2/(MI1+MI2) where MI1 is the m.i. of the ball, MI2 the m.i. of the the moment of inertia of the bat. Therefore, in this part of the swing heavier bats are better, up to the point at which the bat is too heavy to be brought to the max speed.
The second part of the swing is the brief moment of impact. During this time, the total moment of inertia will be the moment of inertia of the bat added to the moment of inertia of the ball (the farther the ball is from the batter, the more force it takes to move it). The ball will therefore receive a force proportional to MI1/(MI1+MI2). The lighter the bat, the more force the ball receives, but this advantage becomes less and less important the lighter the bat.
So in the first part of the swing, heavy bats are good, at least up to a point. In the second, heavy bats are bad. Which part will count for more will depend on many factors, such as arc of swing, arm strength, amount of ball deformation, etc. Of course, this is just a cursory analysis, so it doesn’t come with any guarantees.
BTW, what’s the URL of the column that started this?
-Ryan
" ‘Ideas on Earth were badges of friendship or enmity. Their content did not matter.’ " -Kurt Vonnegut, * Breakfast of Champions *
Ryan – I have now modified the first post in this topic to provide the link. Thanks for your comments and for pointing that out. The “please provide link” policy just started in the last few weeks, so some of the older threads don’t have it. If I get some spare time, I’ll try to go back and correct.
If anyone wants to see what is going on when the bat and ball meet, there is an excellent photo of it taken by the old master of high-speed stop photography, Harold Edgerton, of MIT. I imagine most any physics text would have it in the chapter on collisions. The ball deforms quite nicely around the barrel of the bat.
By the way, most of you seem to be ignoring the factor of strength of the batter in the equation. On one hand, strength will help increase bat speed for heavier bats. But on the other hand, strength will help power the bat through the collision. Thus, even if I can swing a 35 ounce bat to ‘maximum’ velocity at initial impact, I may prefer a lighter bat which will be easier to force through the ball during the time of impact. Someone with WAY more understanding of collisions would have to calculate the relative importance involved.
The question of heavy v light bat has not been resolved to everyone’s satisfaction.
I humbly submit the following for your consideration:
a: The benefits of each cancel out.
b: The benefits of each very nearly cancel out.
c: It depends on the circumstances. (the batter, the pitcher, the humidity, etc.).
d: Unknown variables. (Suns spots, Camllurdian phase loops, inverse dimensional di-polarity, etc.).
You are unique - Just like everyone else.
Both are valuable…
You want a light bat if you’re trying to get rid of pesky insects.
You want a heavy bat if you’re trying to dispose of rotting fruit.
Oh, wait a minute, you mean the other kind… 