Re: [Phys-l] Energy Transfer with hammers

["Bill Nettles" <bnettles@uu.edu>]

Seems to me the two factors involved in comfort would be the weight of the hammer (having to lift and swing from a variety of positions)and the radius of gyration (some people would say location of the "sweet spot") which would affect the rebound effect. If you've ever hit a baseball at the wrong location on the bat, you know how irritating that can be. Lot's of energy transferred back to the hands and arms.
 
Titanium would definitely be the material of choice for weight versus yield strength.  I haven't done a calculation to see how the reduced density would affect the sweet spot location.
 
Bill N

> > > Jack Uretsky <jlu@hep.anl.gov> 7/14/2009 10:47 am >>>
Hi all-
I do not understand "energy delivered to the target".  I would 
assume that the recoil energy of the hammer, after  impact with the nail, 
is not "delivered to the target".  With my intermpretation, the energy 
actually delivered to the target is mesured by the depth to which the 
"target" is driven.
What is the relation, if any, of the recoil of the hammer with the 
comfort of the workman?  What are the mechanical factors the affect the 
workman's comfort?
Regards,
Jack



On Tue, 14 Jul 2009, chuck britton wrote:

> from the wikipedia's 'hammer' article.
>
>
> Effect of the head's mass
>
> The amount of energy delivered to the target by the hammer-blow is
> equivalent to one half the mass of the head times the square of the
> head's speed at the time of impact (E={mv^2 \over 2}). While the
> energy delivered to the target increases linearly with mass, it
> increases geometrically with the speed (see the effect of the handle,
> below). High tech titanium heads are lighter and allow for longer
> handles, thus increasing velocity and delivering more energy with
> less arm fatigue than that of a steel head hammer of the same weight.
> As hammers must be used in many circumstances, where the position of
> the person using them cannot be taken for granted, trade-offs are
> made for the sake of practicality. In areas where one has plenty of
> room, a long handle with a heavy head (like a sledge hammer) can
> deliver the maximum amount of energy to the target. But clearly, it's
> unreasonable to use a sledge hammer to drive upholstery tacks. Thus,
> the overall design has been modified repeatedly to achieve the
> optimum utility in a wide variety of situations.
>
>
> but hammers are already available in a variety of masses - from tack
> hammers to sledge hammers.
> Titanium allows a smaller mass while maintaining the same size
> striking surface.
>
> Do lighter traditional framing hammers have a smaller head?dunno
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