[TheForge] treadle hammer design (was: treadlehammeranvils)

Sat Jan 25 02:00:00 2003

At 01:23 PM 1/24/03, you wrote:

Bruce;
I think randy was proposing the sprung pivot arm for "whip" rather than 
return. In either case it would be a mess except at the one speed the 
harmonics  of the system worked out to. Why bother with the weight? just 
fasten the end of the  long spring  arm down .
I overcame some of the shortcomings of the Abanana plans by lengthening the 
arms a fair amount and using  a taller hammer shaft and backbone. It is , 
however slower and heavier, but then, so am I. If I had another one to 
build, I'd either try for your grasshopper or an in-line variation.
Let's recognize George's splendid mastery of the TH...he is awful damn good.
His  demo  in SLO was the first time I saw or heard of a TH and I was 
WOWed!  Went home with my head buzzing and clanging and It wouldn't stop 
till I built one out of available materials.
As you pointed out, those of us with less skill or talent take refuge in 
tooling.......Pete

>Randy,
>
>Right!  You'd STILL need a snappy spring to provide return force.  The 
>counterbalancing alone won't do it.
>
>But in addition, you would have to have really tight pivot bearings to 
>ensure that the counterweight mass would add to the ram mass in providing 
>the blow.  Any slop anywhere and you'd lose impact force.
>
>Bruce
>NJ
>
> >>> [email protected] 01/23/03 02:54PM >>>
>I built a treadle hammer from the ABANA plans a few years ago , at that time
>I also thought about a counter ballance arrangment. It sure seems like two
>25lb weights on either end of an arm would move as fast as one 50lb wt on
>one end. Of course you would need enough spring tension to raise the hammer
>rappidly, this not just a balancing act. If the arm between the weights was
>a leaf spring it might add some life to the whole affair.
>Randy Mundt
>----- Original Message -----
>From: "Bruce Freeman" <[email protected]>
>To: <[email protected]>
>Sent: Thursday, January 23, 2003 7:18 AM
>Subject: Re: [TheForge] treadle hammer design (was: treadlehammeranvils)
>
>
>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
> >
> >
> >_______________________________________________
> >http://mailman.qth.net/mailman/listinfo/theforge
> >theforge mail list group photo site is
> >http://www.photoaccess.com
> >Login:  [email protected]
> >password:  anvil
> >___________
>
>
>_______________________________________________
>http://mailman.qth.net/mailman/listinfo/theforge
>theforge mail list group photo site is
>http://www.photoaccess.com
>Login:  [email protected]
>password:  anvil
>___________
>
>
>_______________________________________________
>http://mailman.qth.net/mailman/listinfo/theforge
>theforge mail list group photo site is
>http://www.photoaccess.com
>Login:  [email protected]
>password:  anvil
>___________
>
>
>
>
>_______________________________________________
>http://mailman.qth.net/mailman/listinfo/theforge
>theforge mail list group photo site is
>http://www.photoaccess.com
>Login:  [email protected]
>password:  anvil
>___________
>
>
>_______________________________________________
>http://mailman.qth.net/mailman/listinfo/theforge
>theforge mail list group photo site is
>http://www.photoaccess.com
>Login:  [email protected]
>password:  anvil
>___________