[TheForge] treadle hammer design (was: treadlehammeranvils)

[Marc Godbout]

I've been following this thread and need some clarification on why a
counterbalanced hammer would be slower than a spring return one. 

The original question asked if, instead of a 50lb ram, you had a 25lb
ram with a 25lb counterweight. The mass stays the same, so, not counting
gravity, the same acceleration would take the same force. And it would
then result in the same hitting force.

If you throw gravity at it, yes, you have to "lift" the counterweight,
but you also have to stretch the springs. The net desired effect is to
have the hammer at near-zero gravity in both situations. So gravity is
canceled out.

I'm not refuting any claims, just need to understand. I've got a degree
in EE, so that naturally makes me an expert in all things scientific :-)

-Marc

On Thu, 2003-01-23 at 12:06, Bruce Freeman wrote:
> Larry,
> 
> I'm not absolutely sure I follow you, especially about that trap door, but I think what you mean by "the acceleration aspect that becomes a problem" is the fact that the user has to accelerate the ram, rather than gravity doing it.  Obviously true.  
> 
> But not a problem at all.
> 
> It simply is not that difficult to accelerate a weightless mass.  We accelerate hand-held hammers all the time.  See how much work you get from a hand-held hammer if you let gravity do all the accelerating.  Not much!  So we typically fling hammers down on our work with considerable acceleration.
> 
> Having  worked a bit with a weightless 16-lb sledgehammer, I can assure you that even accelerating that without gravity's help is no big deal.  
> 
> Now, accelerating a 50-70-lb ram with your foot is no big deal either.
> 
> Bruce
> NJ
> 
> >>> thedragons@dragonswatch.com 01/23/03 11:38AM >>>
> Hi Bruce,  Pete,
> 
>     I thought about the speed thing, it is the acceleration aspect that becomes a problem.  Some thing about a mass at rest........ I thought about using a pulley arrangement where one end anchors to the frame and the other to the ram or some where between and the pulley to the treadle.  I think this is how you did the grasshopper.  At any rate it works well on a trap door for one of my shops.  I can see that when the ram is moving with gravity then acceleration occurs naturally,  and when the weight is moving both up and down
> 
> then the task of acceleration becomes completely upon the operator.  Hence the slow moving ram.  In as much as speed = impact force, I see where this becomes the factor in limiting efficiency.  More thought must be applied.  Thanks for your insights and experience.  Maybe with a little combined effort, we can like this dog yet.
> 
> Larry
> 
> Bruce Freeman wrote:
> 
> > Larry and Artgawk(?):
> >
> > Good thinking, but I'm ahead of you on this one.
> >
> > I actually tried a counterbalanced hammer back in 1997 or so.  (It might have worked as a treadle hammer, but I had rigged it up as a hand-held hammer.) With RIGID connections (including no slop in the pivots) such a machine might work, but it was my impression that Artgawk's (OK, what's your REAL name?) intuition about slower BPM is right on.  The thing moved VERY slowly.  So slowly, that all advantage of using a heavy hammer was lost.
> >
> > In that respect, please consider that momentum = m*v, but work = energy = mv^2 = (m * v-squared); where m = hammer mass and v = hammer velocity at impact.  Hence the speed of the hammer is (within limits) much more important than the mass.  (Useful work is a different concept:  A bullet may do more "work" than a single blow from a power hammer, but I don't see anyone changing over to machine-gun smithing!)  I readily demonstrated to myself that a slow-moving 16# slegehammer was MUCH less useful than a hand-held 2-lb hammer.
> >
> > In designing the Weightless Hammer (a hand-held sledgehammer), 
> 
> 

-- 
Marc Godbout
http://www.ironringforge.com

New England Blacksmiths Membership Director
http://www.newenglandblacksmiths.org