Thread: Make a Mallet (Shopnotes)
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dpb dpb is offline
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Default Make a Mallet (Shopnotes)
On 2/20/2014 10:47 AM, wrote:
I hate to keep kicking this horse but... I just received my
electronic issue if Popular Woidworking today. An article on mallets
was on theinside. What a coinkydink.

On the topic of dead blows the cabal says:

"Minimal rebound makes better use of the applied force"

How do I get a better use of force here? How did this myth start? I
want to blame someone. Norm? Can I blame Norm?

Again if F = ma. And I apply the m a little at a time apposed to all
at once, how is this a better use of the applied force? ...

You _really_ don't want to get more into the physics of hammers, trust
me...

But, besides the conservation of energy, there's conservation of
momentum to be considered and the transfer of energy from/to the target
is also a dependent on the characteristics of both the driver head and
the target.

And, the actual force is an impulse wherein the motion of the hammer
comes to rest in a distance that is dependent on the resistance of the
target--the more resistant, the shorter the distance moved and the
higher the delivered force because that resisting force times the moved
distance must be the same as the kinetic in the hammer to balance the
energy.

A well-designed dead-blow hammer has most of the mass in the head in the
innards so the actual head has essentially come to rest when the
internal mass then delivers the blow. The effectiveness comes from the
more effective transfer and less recoil energy that doesn't go into the
target with a conventional hammer head.

And, that's all I'm going to say and I'm _not_ going to go into a
full-blown analysis...if I still had access to a nonliner FEA system I
might be inclined to set up a couple or three examples that could show
what happens w/o having to actually set up the detailed analytical
solution, but having returned to the farm from the consulting gig I
don't. It's a lot like a simplified case of the collision analyses the
major auto manufacturers go through where they actually use such to help
design survivability into their vehicles...

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