BASEBALL BATS
BASEBALL BATS
(OP)
Having spent 30 years making the world safe for steel and concrete <Grin> (Structural Engr., PE, & graduate degrees), one of my diversions for the past 20 years is to umpire baseball (not enough abuse in engineering – go figure). Here’s the issue, it should be fun – an interesting application of engineering mechanics.
All age groups - up to 18 years old - use metal bats. Visibly cracked metal bats are not allowed for play (makes sense) but dented metal bats have become an issue for controversy. Typically, umpires have not allowed dented metal bats for play after doing pre-game equipment inspections.
This year, Little League Baseball (Williamsport, PA), says that if a dented metal bat passes through a circular ring whose diameter matches the major diameter of the dented “tapered” metal bat (2-3/4” down to about 1” at the handle), the dented metal bat should be OK for play.
Without biasing the discussion, too much, with my own specific concerns that I’ve expressed to other umpires of various backgrounds and education levels, what are your thoughts as technical professionals? Would you feel comfortable addressing a safety issue by measuring only the major bat diameter when the dent can be anywhere along the bat? Is the lack of an outer surface crack sufficient? Bats are, typically, hollow, thin-walled aluminum alloys. And, yes, metal bats have been known break on impact although nothing close to the frequency of wooden bats.
All age groups - up to 18 years old - use metal bats. Visibly cracked metal bats are not allowed for play (makes sense) but dented metal bats have become an issue for controversy. Typically, umpires have not allowed dented metal bats for play after doing pre-game equipment inspections.
This year, Little League Baseball (Williamsport, PA), says that if a dented metal bat passes through a circular ring whose diameter matches the major diameter of the dented “tapered” metal bat (2-3/4” down to about 1” at the handle), the dented metal bat should be OK for play.
Without biasing the discussion, too much, with my own specific concerns that I’ve expressed to other umpires of various backgrounds and education levels, what are your thoughts as technical professionals? Would you feel comfortable addressing a safety issue by measuring only the major bat diameter when the dent can be anywhere along the bat? Is the lack of an outer surface crack sufficient? Bats are, typically, hollow, thin-walled aluminum alloys. And, yes, metal bats have been known break on impact although nothing close to the frequency of wooden bats.






RE: BASEBALL BATS
What condition are the bats in when they break? Perhaps visible cracks are more of an issue than dents.
Have you any idea what aluminium grade the bats are made of?
JHG
RE: BASEBALL BATS
RE: BASEBALL BATS
Why don't you just call a bat manufacturer and speak to someone in their engineering department?
RE: BASEBALL BATS
RE: BASEBALL BATS
I am sure someone there could run you a nice non-linear transient dynamic analysis of an aluminium baseball bat (with and without dents, cracks, etc)
RE: BASEBALL BATS
Call me old, call me a purist, but having used both, I love the wooden ones! especially the bottle bats of old.
RE: BASEBALL BATS
Not going to happen though. The "major diameter" test is not adequate, since baseball bats are tapered with the exception of a short distance on the barrel.
The dent work hardens the area and that can produce faster fatigue failure of the bat. Stresses sufficient to cause denting are likely causing deformation curvature in the handle as well.
My criteria...If dented, don't use it. If bent with handle curvature, don't use it.
RE: BASEBALL BATS
RE: BASEBALL BATS
RE: BASEBALL BATS
Batter up!
RE: BASEBALL BATS
The book discusses the physics of bats, both wood and aluminum as well as pitching, curve balls and the baseball itself.
Here is a quote to think about: "Very large forces, reaching values as high as 8,000 pounds, are required to change the motion of the 5-1/8 ounce ball from a speed of 90 mph toward the plate to a speed of 110 mph toward the center field bleachers in the 1/1000 of a second of bat-ball contact."
So, the condition of the bat, whether wood or aluminum, is a safety issue.
RE: BASEBALL BATS
With dents whose major axis follows the longitudinal axis of the bat the above problem is only a minor issue as the radius at this location is relatively large. Moreover, the indention in the long direction is typically inward and not "pinched"
In summary, the transverse dent will not absorb and transmit energy like it once did. The working hardening and stress riser take care of that. It will crack and break in just a matter of time. The other indentation is not as likely to crack or split and will absord and reflect the energy (assuming the dent opposite to the side hitting the ball) but not as efficiently. Rather than get into many arguements about using bats that are dented about so and so axis, I recommend banning dented bats altogether.
Regards,

Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: BASEBALL BATS
To give you an idea, we use an A/Y ratio of 30 to evaluate dents in 2024-T3 aluminum. Any dent with an A/Y ratio over 30 is considered smooth and OK. If the A/Y ratio is less than 30, we cut out the damage and repair the structure (in your case reject the bat).
Example: dent depth .125" - Major axis 2.5 inches /Minor axis 1.5". A/Y = 1.5/.125 = 12 which is less than 30 so dent is no good.
Obviously the A/Y limit of 30 is based on testing and years of service experience with that particular alloy. It would not be appropriate to apply this limit to other alloys.
Another concern to investigate would be bat failure due to thin wall instability in compression. The dent represts an eccentric load path and will add another bending term to the beam equation. Without knowing the actual bending stresses on a bat, I would guess that the handle area would be most critical, with less concern at the upper end.
One more comment and then I'll quit. Visual inspection of the bat will not detect small cracks on the inner surface (where I would expect cracking to intiate). Other inspection techniques would not be practical. Banning dents altogether seems extreme since, in my experience, they get dinged up just throwing them in the bat bag.