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Barrel-Forearm Alignment

May 24, 2013
9,432
83
So Cal
I read something yesterday that was describing the alignment of the barrel and the lead forearm at contact.

This isn't a detail I have heard discussed before. As I looked through a bunch of pro swings, this appears pretty typical (or close to it).




Thoughts?
 
Last edited:

pattar

Clueless..
Jun 8, 2016
2,373
63
Just a guess but this quote:

"It was shown that the maximum speed of the rod results if
the pendulum arm comes to a temporary stop at the instant
when the rod and the arm are both vertical. In that case, all
the initial potential energy of the system ends up as kinetic
energy in the rod."

from this paper:

https://www.physics.usyd.edu.au/~cross/PUBLICATIONS/29. DPendulum.pdf

might have something to do with it. In the quote the rod is the bat and the forearm is the pendulum arm and
"both vertical" here refers to when they are aligned.

The forearm does not come to rest obviously but it does slow down right before contact if I remember correctly.
 
Last edited:
May 24, 2013
9,432
83
So Cal
Just a guess but this quote:

"It was shown that the maximum speed of the rod results if
the pendulum arm comes to a temporary stop at the instant
when the rod and the arm are both vertical. In that case, all
the initial potential energy of the system ends up as kinetic
energy in the rod."

from this paper:

https://www.physics.usyd.edu.au/~cross/PUBLICATIONS/29. DPendulum.pdf

might have something to do with it. In the quote the rod is the bat and the forearm is the pendulum arm and
"both vertical" here refers to when they are aligned.

The forearm does not come to rest obviously but it does slow down right before contact if I remember correctly.
Science!...
 
Jan 6, 2009
1,976
48
Pacific NW
Just a guess but this quote:

"It was shown that the maximum speed of the rod results if
the pendulum arm comes to a temporary stop at the instant
when the rod and the arm are both vertical. In that case, all
the initial potential energy of the system ends up as kinetic
energy in the rod."

from this paper:

https://www.physics.usyd.edu.au/~cross/PUBLICATIONS/29. DPendulum.pdf

might have something to do with it. In the quote the rod is the bat and the forearm is the pendulum arm and
"both vertical" here refers to when they are aligned.

The forearm does not come to rest obviously but it does slow down right before contact if I remember correctly.
I had a science question for you, although I can't remember what the heck it was now.:confused::confused::confused:
 
May 24, 2013
9,432
83
So Cal
Is it the lead arm and bat are aligned, that the bat is an extension of the lead arm?
As I'm understanding this, the bat reaching a point of being in alignment with the lead forearm at the moment of contact is the goal for maximum bat speed (although just before impact is probably good enough in the real world). Extrapolating from that...The upper arm, forearm, and bat all being in line would be ideal, assuming the parts all reach alignment at/before impact. However, certain pitch locations would be limiting to the ability to achieve 3-part alignment.

(The above is an assumption from someone with a mediocre understanding of physics.)
 

SB45

Dad, Coach, Chauffeur
Sep 2, 2016
134
18
Western NY
In my head...if the bat lags behind as it should, it doesn't catch up to that alignment with the lead forearm until contact...accelerating just at the right time. If the hands start to early, and there is no lag..the bat seems to be aligned with the forearm too early and doesn't have that same acceleration at the point of contact.
 
Jan 6, 2009
1,976
48
Pacific NW
As I'm understanding this, the bat reaching a point of being in alignment with the lead forearm at the moment of contact is the goal for maximum bat speed (although just before impact is probably good enough in the real world). Extrapolating from that...The upper arm, forearm, and bat all being in line would be ideal, assuming the parts all reach alignment at/before impact. However, certain pitch locations would be limiting to the ability to achieve 3-part alignment.

(The above is an assumption from someone with a mediocre understanding of physics.)
I think I gotcha. The alignment is different as usually shown by people of a contact position. What is usually shown is the bat and lead arm aren't a extension of each other. The lead arm is extending out front and the bat is at 90 degrees. It's a poor visual compared to the pics you posted.
 
May 24, 2013
9,432
83
So Cal
In my head...if the bat lags behind as it should, it doesn't catch up to that alignment with the lead forearm until contact...accelerating just at the right time. If the hands start to early, and there is no lag..the bat seems to be aligned with the forearm too early and doesn't have that same acceleration at the point of contact.
The problem is that the typical "bat-lag" approach includes pushing the hands forward, which moves the center of rotation for the barrel, and may make it more difficult to achieve bat-forearm alignment. Early barrel speed and a deep turn leads to the position you see Khris Davis in (bottom right in the pic above). You can't get there if you lag and push.

I'm not sure how much velocity penalty there is for getting to alignment early and carrying that velocity through contact, but I suspect that's a better trade-off than being late. One thing I also see with hitters (including my DD) who aren't getting to alignment before contact, is that the hands often are moving left around the body and pulling the barrel laterally across the ball during contact, which costs power.
 

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