bat weight vs. length

[Amy in AZ.]

So, as not to high jack someone's thread about bats, I will post this here. This is something that I saved from 5 yrs. ago. I don't know the poster, but he put some work into this. His name is mike connor.




Weight is possibly the most important factor in selecting bat size. I listed Length first because that needs to be established before the weight is selected. The reason for this is that the length and weight combined together effects the “swing weight” or for the physicists out there, the "moment of inertia" (MOI). The swing weight of a bat is basically determined by the length of the bat and the weight of the bat (plus other factors, including where the weight is distributed along the bat (aka center of mass), choking up, end loading, barrel length, etc.). Two bats of different brand/model may have the same length and weight, but have very different MOI. End-loaded bats will have a different MOI than ones that are not end-loaded. In that case, the end-loaded bat will feel heavier when swinging (bigger swing weight or MOI).



What we are looking for when we select a bat weight and length is a combination that allows the player to hit the ball the farthest/hardest, and depending on their hitting style (power hitter or high average hitter). The two key factors in imparting energy to the ball are mass (weight) and velocity (bat speed). Weight has a linear effect on the ball and bat speed has an exponential effect on the ball. In other words, bat speed is more important than weight in determining how far a ball is hit. The ideal combination is one where maximum energy is imparted, which is accomplished by the heaviest bat that can be swung at maximum speed. The best way to determine this is to find a place that can measure your bat speed and bats of various lengths, weights, and end loading. Starting with a bat of the correct length and a few ounces lighter than you think is the right weight, take a few swings and see what the bat speed is. Do this for bats of different weights until you get to the point where your bat speed starts to drop off noticeably. When you reach that point, a bat 1 ounce less is about the optimum weight (If your speed dropped when you went to a 22 oz bat, you should select a 21 oz bat, or possibly a 22 oz if the drop was small).

 

[Amy in AZ.]

Con't.


Another consideration has to do with what the bat speed is at various points throughout the swing. Some hitter/bat combinations may have peak bat speed early in the swing, then tapering off as the swing progresses. Others may peak later in the swing. Obviously the max benefit comes when max speed is at point of impact with the ball. Measuring the bat speed at various points in the arc of the swing is difficult and requires some specialized equipment not readily available. The MOI of the bat definitely has impact on the point at which max speed is obtained. By and large, this is taken care of by having good swing mechanics and the right bat length/weight.

Since few places offer this kind of bat speed measurement, the next best thing is to try to determine that point between the player and yourself. As she swings heavier bats, or even same length & weight bats that have different end loading, tell her what she is looking for (that feeling of heaviness, slowing down, or resistance) as you observe. You may not be able to tell much about the bat speed until she gets a bat that is more than 1 oz too heavy, but she should be able to feel a difference and if a bat is exceptionally heavy her swing mechanics will likely start to fall apart (due to the bat weight causing her bat to be delayed in getting through the hitting zone). My experience with my daughter is that when we used a 24 oz bat she started hitting balls into the ground more frequently. We dropped back to a lighter 22 oz bat and more of the hits became line drives.

As with selecting length, there are charts for selecting bat weight, usually based on body weight of the player. While weight of the player has a loose correlation of with strength, it falls apart for kids that don’t fit the profile selected by the chart maker. Those charts are starting points of what weight bat to select, but swinging the bat is still recommended.

Another consideration for what weight to select is to determine what type of hitter the girl is. A little lighter bat allows for a bit more bat control, which would be helpful for higher average hitters. Power hitters may give up a slight bit of bat control in order to have maximum power. Remember that no consistent rules seem to apply for all hitters. Babe Ruth used a MASSIVE bat and held 1 or 2 fingers below the knob for much of his career to hit his 714 home runs, while Barry Bonds (the single season Home Run record holder) uses a fairly short and light bat and chokes up. This gets back to my belief that the psychological aspects (a bat that “feels” right for them) matter most. Maybe a “pretty” bat matters most for some hitters???

There has been some discussion about barrel length and the pros and cons of longer/shorter barrels. Some bats, like the DeMarini Medusa, are shaped like what used to be called a “Bottle bat.” Theses bats have an exaggerated barrel length compared to typical bats. While a typical 32” bat may have a barrel length of 11 to 12.5”, the 32” Medusa boasts a barrel length of 18”. A longer barrel increases the hitting area slightly, but is the added hitting area in a location (towards the grip) that will make much difference?

The Center of Percussion (COP) is generally considered to be the “Sweet Spot” of the bat. Sweet Spot is a loosely defined area where the ball comes off the bat with maximum speed. In most cases this is located at approximately the center of the length of the barrel. The sweet spot is generally a fairly small length of the bat, usually no more than a couple of inches. Exactly where the sweet spot starts and stops is open to interpretation. When a bat has a longer barrel length a couple of things happen. First, the COP (sweet spot) actually gets moved closer to the handle, since the center of the barrel is lengthened. The center of a 12” barrel would be 6” from the end of the bat, while an 18” barrel would be 9” from the center of the end of the bat. For maximum power you might sample where the batter typically hits the most of the balls. If the most frequent location of ball contact is 5” from the end of the bat, you might consider a bat with a barrel in the 12” range. If she hits closer to the handle then a longer barrel may put her in the best position for more solid hits. Some bats use the same shell/barrel for bats of all overall lengths, while some bats keep the barrel in proportion to the overall bat length (e.g., the Synergy barrel has a half inch difference in barrel length for every inch of overall length).


• Rotate the bat 1/8 or 1/4 turn each swing. Hitting the ball on the same side of the bat each time can cause denting. Some bats have “Index Marks” (usually 8) just above the handle to help keep track of how much to turn the bat each time. You can use a marker to put your own index marks on the bat. I put them just above the handle.

These are just some things that I thought might be helpful. The info comes from a variety of sources, some are more scientific in nature, some from bat manufacturers, and some is anecdotal. There are a great many factors that come into play, some which matter more than others. At the end of the day, hitting is still about the player more than the equipment.

The charts are available on the internet in a number of places. Some additional resources that you may find helpful include:

http://www.npl.uiuc.edu/~a-nathan/pob/SwingSpeed.pdf - A Study of Softball Players Swing Speed

Swing Weight: Why moment-of-inertia matters more than weight - Swing Weight of a Bat:
Why moment-of-inertia matters more than weight

Physics and Acoustics of Baseball and Softball Bats - Physics and Acoustics of Baseball and Softball Bats. Tons of bat info.

Bat Sizing Guide - Coastal Athletic Supply - Bat sizing chart (womens/girls Fastpitch can add 1”)

Bat Care Tips - Bat care tips

What's in an Aluminum Bat Anyway? - Info on the various types of aluminum alloys used in bats (C405, Scandium, Gen1X, SC900, etc.)

Bat Speed -- Baseball Hitting Drills - A web site dedicated to hitting the ball well. Lots of good stuff here.

BAT LENGTH Recommendation Chart (found in various places on the internet):
To find the right bat length, find your height in the chart below. Then find the column with your weight and move across the chart until you come to the header containing your weight. This meeting point, in inches, indicates the recommended bat length for you.
Bat Length Sizing Chart
Height (in) 49-52 53-56 57-60 61-64 65-68 69-72 73
Weight (lbs) Bat length
under 60 27" 28" 29" 29"
61-70 28" 29" 30" 30"
71-80 28" 29" 30" 30" 31"
81-90 29" 30" 30" 31" 32"
91-100 30" 30" 31" 31" 32"
101-110 30" 30" 31" 31" 32"
111-120 30" 31" 31" 32" 32
121-130 30" 30" 31" 32" 33" 33"
131-140 30" 31" 31" 32" 33" 33"
141-150 31" 31" 32" 33" 33" 34
151-160 31" 32" 32" 33" 33" 34"
161-170 " 32" 32" 33" 33" 34"
171-180 33" 34" 34"
180+ 33" 33" 34" 34"

 

[RubberBiscuit]

Wow - lots of data!

So we are gonna do an experiment in this domain with my DD. We are going to go from her current CF4 at 33 to an Anderson Rockettech at 34. I am a little nervous on what changes we'll see in her offense. (my DD is 5'10" and 145 and strong).

I like the idea of moving away from composite as I saw soooooo many of them self-destruct last year in the midwest.