Does a shaking hammer blow cause less damage than a stiff blow?

[Username34]

They always talk in boxing and martial arts to stiffen at the moment of impact, but how crucial is this?

By way of analogy, how much of a power leakage results from a hammer shaking at point of impact compared to a stiff one?

Less concentrated force, surely.

 

[Baluncore]

They always talk in boxing and martial arts to stiffen at the moment of impact, but how crucial is this?

That is an impedance matching problem.
You do not want energy reflected from the target, back into the arm or handle.
You want the whole momentum to be transferred. That requires all the moving mass, to be rigid behind the impact, at the one time.

 

[Username34]

That is an impedance matching problem.
You do not want energy reflected from the target, back into the arm or handle.
You want the whole momentum to be transferred. That requires all the moving mass, to be rigid behind the impact, at the one time.

How much force is dissipated by shaking/instability? All else equal

 

[Baluncore]

How much force is dissipated by shaking/instability? All else equal

The mass of the head of the hammer is the minimum momentum. The maximum momentum is the mass of the hammer head, handle, and your arm. Let's call that a factor greater than two.

It is not the failure to deliver energy that is the problem. It is the damage to your body caused by the reflected energy. The reflected energy can exceed the energy transmitted into the target, so you may be doing more damage to yourself than to the target.

 

[berkeman]

By way of analogy, how much of a power leakage results from a hammer shaking at point of impact compared to a stiff one?

I agree with the impedance matching comments by @Baluncore -- that would seem to be the key point.

Do you have a hammer? All you need are some nails and a few pieces of scrap wood to conduct your own experiments. Try holding the hammer loosely and see how far the nail is driven into the wood with each blow. Then hold the hammer with a stiff rigid wrist and re-do the experiment. Then try to find the best middle ground between those two to give you clean-feeling blows to see if the nail is driven the furthest with those.

People who use a hammer as part of their jobs in the trades learn pretty quickly how best to swing a hammer...

 

[Username34]

I agree with the impedance matching comments by @Baluncore -- that would seem to be the key point.

Do you have a hammer? All you need are some nails and a few pieces of scrap wood to conduct your own experiments. Try holding the hammer loosely and see how far the nail is driven into the wood with each blow. Then hold the hammer with a stiff rigid wrist and re-do the experiment. Then try to find the best middle ground between those two to give you clean-feeling blows to see if the nail is driven the furthest with those.

People who use a hammer as part of their jobs in the trades learn pretty quickly how best to swing a hammer...

Does tension before impact increase velocity or is that just a perception?

 

[berkeman]

Tension of what?

 

[Lnewqban]

There is a reason for the handles to be made of wood or fiberglass: action-reaction Newton’s law.
Your skin, muscles and bones absorb the remaining returning energy, so you don’t feel like you are hammering your own brain.

Martial art practicers increase skin toughness and bone density, and improve positioning of hands and feet bones via stong muscles, in such a way that softer joints tissue does not get damaged.

 

[docnet]

I remember seeing posts about bendy hammers on social media. It claimed that bendy hammer handles lead to better kinetic energy. It seems related to this topic.



Though, I have never seen a bendy hammer in real life.

 

[berkeman]

Though, I have never seen a bendy hammer in real life.

^^^^ This.

 

[berkeman]

Though, I have never seen a bendy hammer in real life.

Actually, this brings up a larger question about impacts, but I don't know if we want to go there in this thread. Maybe a different thread? How do you optimize energy transfer in manual impacts for different scenarios...?

http://www.golfclubshaftreview.com/

 

[Hornbein]

I remember seeing posts about bendy hammers on social media. It claimed that bendy hammer handles lead to better kinetic energy. It seems related to this topic.



Though, I have never seen a bendy hammer in real life.

I believe it. .My knowledge is about golf clubs and swings. For the golf swing it is key for your joints to be loose and relaxed. The club head lags behind your hands and arms then naturally catches up, ideally reaching a peak at the time it encounters the ball. Golf club shafts are flexible for the same reason. Weaker golfers use more flexible "whippy" shafts. Using a sledgehammer or hitting a baseball works the same way. The mistake most beginners make is tensing up and trying to muscle the ball. A relaxed smooth swing is much better. Once you've got that you can speed it up gradually.

Hitting the ball or whatever precisely in the center of percussion of the club or bat or whatever is important too. This avoids energy-absorbing lateral vibrations in the club or bat. Golfers call it "hitting it pure." Ray Guy once punted a football so "pure" it hit the dome of the Astrodome. He said he felt less impact on his foot than usual.

I don't know that this has anything to with martial arts.

 

[Baluncore]

A sledgehammer impact takes only an instant, in that the non-linear impact generates many high frequency harmonics. If permitted to enter your body, those harmonics would jar and damage you.

The hammer handle needs to act like a flexible low-pass filter, that allows the fundamental sinusoidal energy input from your body, to reach the head of the hammer, but blocks the reflected harmonics from propagating through the handle, back to your body.

The attachment of the hammer head to the handle will be a point of energy reflection. That junction must be designed, so the handle does not break at the head when used by a normal person. Abnormal people will break handles, until the handle is replaced by a steel pipe, that punishes them harmonically, for hitting too hard.

By locking your straight arm rigid, as you punch, you prevent energy reflection, causing damage to your joints. You also have the greater moving mass of the whole limb against the target. The important thing is to estimate the follow-through expected, so you do not over-extend or stop short at first contact. The longer the contact takes, the more energy you can transfer without damage to your arm.

https://en.wikipedia.org/wiki/Dead-blow_hammer

 

[Rive]

They always talk in boxing and martial arts to stiffen at the moment of impact, but how crucial is this?

No general answer. Some techniques are focused on maximal impact damage, others are focused on speed and utilizes the reflected forces to draw back and some are about maximal transferred momentum (to sweep a leg, for example: without breaking your own).