[TheForge] treadle hammer design (was: treadlehammeranvils)

Thu Jan 23 11:44:03 2003

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), I overcame this speed problem by using a 24"/4" pulley(-sprocket) speed increaser.  Although the Weightless hammer employs a garage-door spring to balance the hammer, the concept works just as well with a heavy weight (16 lb. x 24" / 5" = ~100 lb) (but is a lot more awkward and less portable).  This works:
>
> http://www.monmouth.com/~freeman/wh/wh.htm
>
> Responding to Larry's original post:  I previously designed a more elegant weightless treadle hammer, namely the Grasshopper Treadle Hammer:
>
> http://www.monmouth.com/~freeman/bmf/grashopr.htm
>
> In this case I still use (4) garage door springs to balance the weight of the ram.  Again, this is mostly for practical reasons.  A weight would have been easier to design in (as it doesn't change its force as it changes position) but I would probably have needed a several-hundred-pound weight for the purpose.
>
> I went one step further here.  You don't really need ANY continuous spring force to lift a weightless ram.  You only need an initial acceleration.  In an ideal world, the bounce you get when the ram hits the anvil might be enough.  However, you can't count on that, especially when some hot metal will absorb all the impact.  Therefore, I designed in an adjustable "kickback" force mechanism.
>
> This kickback mechanism is equivalent to the ram - a the bottom of its stroke - coming down on and compressing a short, light spring.  When the momentum of the ram was dissipated in the work, this spring would then push the ram back up, but the push would only be for a short time.  However, "an object in motion tends to remain in motion," so this is sufficient to carry the ram all the way back up.
>
> The action of this mechanism is clear in the animation:
> http://www.monmouth.com/~freeman/bmf/GHanimNW.htm
>
> Enjoy,
>
> Bruce Freeman
> Nj
>
> >>> [email protected] 01/23/03 04:02AM >>>
> At 02:29 PM 1/22/03, you wrote:
>
> Thought about doing the same thing. Figured that the set up would require a
> much heavier frame and base plate as well as  a massive pivot mechanism and
> lever arm...thought about making the weight adjustable along the arm.
> The advantages would be, not only double mass, but also a slower, more
> penetrating blow. Disadvantages would include slower BPM , cost and loss of
> portability...cause you sure would have to tie that dog down.
>
> >I have looked at the designs of several different styles of treadle
> >hammer.  And they all seem to have one thing in common, some sort of lever
> >and large springs which lift the hammer, and a treadle to over come the
> >springs and lower the hammer.  So I ask, what would be the result if the
> >springs were replaced with a weight great enough to balance the
> >hammer.  Then a light spring could lift the hammer.  Say a conventional
> >design has a hammer of 50# and the operator can accelerate that weight to
> >say 5 fps and the travel is 8 inches.  You would have an
> >impact of XXX pounds per sq. inch.  If you had a hammer where the head was
> >balanced, say 25# hammer and 25# counterweight, would it not strike at the
> >same pounds per sq. inch when moving at 5 fps?
> >This does require the ram and the weight be rigid to each other.  The
> >point being is that you still have 50# of mass in motion, and the energy
> >is transferred in the blow, not in the motion of the head.  Seems
> >somewhere it is written that a mass in motion will remain in motion, or
> >something like that.   Just something to think about.  I'm sure I am over
> >looking some obvious law of physics that says this is not how things work.
> >
> >Larry
> >
> >
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