[TheForge] weight vs speed, or momentum vs energy (Was HAmmer HAndles)

Tue Jan 13 11:29:02 EST 2009

Yes, I know it was a big hammer.  I didn't say it wasn't.  My point is that 
he was maxing out the hammer speed, not the hammer weight.  He obviously 
could have lifted a much heavier hammer, but he (wisely) chose to move up in 
hammer speed before moving up another weight class in the hammer.

Just in case the horse isn't dead yet, let me point out something that I 
should have picked up  about the example we batted around the other day: the 
10,000 pound hammer moving at 2" per second vs the 1 lb hammer moving at 
200" per sec.  Same energy, different momentum, it was posited that the 
heavier hammer would do more work because the greater momentum, despite the 
fact that the little hammer has the same kinetic energy.  What I missed was 
the obvious case of equal momentum in a massive object and in a light one.

OK, so the momentum argument says that if the momentum is equal, they  do 
the same work on impact.       Let's see if that feels right.  At 2" per 
second (V), the 10,000 lb (M) hammer  has 20,000 (MV) inch/second-pounds of 
momentum. 2" per second is a little over 1/10 mph.  So how fast does the 
little hammer have to be going to achieve the same momentum.  MV = 20,000, 
M=1 so V=20,000.  The little hammer has to be moving at 20,000 inches per 
second to have the same momentum as the big hammer.  That's 1600 feet per 
second. Thats 1100 mph.  In case there's any doubt about which would do more 
work, consider this: 1600 fpsis the muzzle velocity of a high end (425 gr) 
.45 magnum round  leaving a 10" barrel.

That's  a one-ounce round traveling at 1600 fps.  Anyone familiar with what 
a 45 mag round can do to say a v-8 engine block can imagine what a 1 lb 
projectile could do at the same velocity . Would the 10,000 lb hammer moving 
at 1/10 mph do that? Remember: they have the same momentum.

For comparison, our little hammer has about the same energy as a 20 mm 
anti-tank round at the muzzle, and around five times the mass.  Both the big 
hammer and the little hammer have about twice the momentum of the 20mm 
round.

So the ultimate question becomes, which would move more hot metal:

(A)  A 10,000 lb hammer dropped a small fraction of an inch or

(B) a 20 mm cannon fired point blank.  Twice.

If momentum is the key to work, then the answer is "neither".  If energy is 
the key, then its (B) the cannon.

And vice versa.
----
- Original Message ----- 
From: "Peter Fels & Phoebe Palmer" <artgawk at thegrid.net>
To: "Blacksmithing List Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Monday, January 12, 2009 4:15 PM
Subject: Re: [TheForge] Wooden Hammer Handles

> It was a big hammer Peter.
>
> Peter Hirst wrote:
>> Rereading this convinces me:  note from this description that Rick was 
>> not
>> using the heaviest hammer he could lift, but he was moving it as fast as 
>> he
>> could "Then he shoved it straight up as high as he could reach on his tip
>> toes
>>> before jerking it back down to start the down stroke".
>>
>> He is getting maximum energy through hammer speed, not weight.
>>
>>
>> ----- Original Message ----- 
>> From: "ries" <ries at riesniemi.com>
>> To: "Blacksmithing List Sponsored by ABANA" <theforge at mailman.qth.net>
>> Sent: Sunday, January 11, 2009 11:54 AM
>> Subject: Re: [TheForge] Wooden Hammer Handles
>>
>>
>>> That Rick is a sneaky little feller- he's stronger than he looks.
>>> He has to be, to keep up with his students- He runs the only graduate
>>> level blacksmithing course in the USA, about 7 of em right now
>>> (students, that is) along with another60 to 80 undergrads.
>>> I spent a weekend with em this fall, and them kids who want to be
>>> blacksmiths bad enough to pay big bucks to study it at a major
>>> university- they are a wild, tattooed, pierced, hard drinking, heavy
>>> hammer swinging bunch. And thats just the girls.
>>> The boys,  well, look out.
>>> And Rick keeps up with, in fact, usually surpasses em, in just about
>>> every category. Although I didnt see him riding a hand forged
>>> motorcycle, although I wouldnt put it past him.
>>> He was up later, and then up earlier, than any of those 20 somethings,
>>> and liquid consumption on his part seemed to run equal as well.
>>>
>>> Ries
>>>
>>>
>>> On Jan 8, 2009, at 10:56 PM, Peter Fels & Phoebe Palmer wrote:
>>>
>>> At a CBA demo years ago, Rick Smith drew out a billet of fancy pattern
>>> welded steel in one or 2 heats using a big hammer ( 6-7#s? or more). He
>>> struck so many hard blows for such a sustained period that the
>>> spectators started rubbing their arms and shoulders unconsciously.
>>> He was not a real big fellow and i was amazed.
>>> It looked like  he didn't begin lifting the handle at the moment of
>>> impact like i usually do, but rather, waited while the rebound rotated
>>> the handle to a nearly  vertical orientation. So when he began his lift
>>> the hammer head was oddly  close to his chest, balanced atop the handle.
>>> Then he shoved it straight up as high as he could reach on his tip toes
>>> before jerking it back down to start the down stroke. Almost seemed like
>>> he was hanging from the handle at the apex.
>>> He moved a very impressive mass of steel...
>>>
>>> No Jerry, it wasn't Handel's 4th movement...he did that in private..pf
>>>
>>> Mike Spencer wrote:
>>>> "David Childress" <trollkeep at gmail.com> wrote:
>>>>
>>>>> My first blacksmithing instructor claimed that handles should not
>>>>> matter.  If the hammer head was below your shoulder you should just
>>>>> be
>>>>> guiding it.
>>>> That's interesting.
>>>>
>>>> I had a very clear notion of just what my hammer and I were doing
>>>> during a blow and even wrote up a description for someone once.  I was
>>>> really quite sure that I had an excellent intuitive grasp of what has
>>>> happening.
>>>>
>>>> Then I got a chance to shoot some high-speed images of hammering and
>>>> discovered that I was completely wrong.  See:
>>>>
>>>>   http://home.tallships.ca/mspencer/hammer.html
>>>>
>>>> and in particular:
>>>>
>>>>   http://home.tallships.ca/mspencer/vec.html
>>>>
>>>> where measurement taken from the images indicate that the hammer head
>>>> is still accelerating below shoulder height.  Those images were made
>>>> at a time when I was regularly doing a lot of hammering and was as
>>>> much in "top form" as I have ever been.
>>>>
>>>>> when the head hits the only force should be from the
>>>>> change of direction.
>>>> Allowing a large margin of error for possibly sloppy measurements, the
>>>> vector diagram suggests that's true only near the very end of the
>>>> hammer's flight path.
>>>>
>>>> I've never been strong enough to work for very long with a 5# hammer
>>>> unless I use it very differently from the way I swing my favored
>>>> 2-1/2# hammer.  At a demo, I was once dared to prove I could do a nice
>>>> upset right-angle bend with properly radiused inside and sharp
>>>> outside, in 1/2" x 2" and accurately positioned at a predetermined
>>>> place.  I did it easily in one heat with a 5# hammer but I couldn't
>>>> keep that up for very many heats.
>>>>
>>>>> He believed in heavy hammers and gravity, your strength should be in
>>>>> lifting the thing up to drop it again.
>>>> There was a blacksmith in Lunenburg, NS, an elderly guy when I met him
>>>> circa 1970, who did essentially that.  He used what I took to be a 5#
>>>> or possibly even heavier (diagonal-peen on one face) hammer with a
>>>> very short handle [1].  He raised the hammer to about shoulder height
>>>> directly over the anvil and brought it down more or less in a straight
>>>> line onto the workpiece, more pushing it or dropping it than swinging
>>>> it.  I thought it an odd and counterproductive style but he was an old
>>>> guy, had been doing it all his life and was still getting orders for
>>>> knives by the dozen.
>>>>
>>>> Another aspect was that he was forging filleting knife blades --
>>>> rather broad and thin -- for the guys at the fish plant, for which he
>>>> may have figured out a particular style that worked for him, the
>>>> particular material and the product.  I never saw him forge anything
>>>> else as he passed away before I got around to paying him another
>>>> visit.  He might have done quite differently forging, say, graplin
>>>> flukes or ring bolts.
>>>>
>>>> FWIW,
>>>> - Mike
>>>>
>>>>
>>>> [1] Or, for Frosty's benefit, haft or helve.  But only scythes have
>>>>    snaths and nibs, okay Frosty? :-)
>>>>
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>>
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>
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