[TheForge] Re: make shift anvil

[GHS]

Tom Troszak, are you out there? This arrangement sounds much like the 
one that gave me so much grief. I lost your explanation or I would just 
post it here.

I live in an urban area and my hammer was about 20 feet from my 
neighbors basement wall. Our soil is heavy wet clay. I set a yard square 
of concrete on a crushed stone base, placed 8X8 timbers on top, followed 
by 3/4 inch high density rubber pad. Sounded good in theory....

What it did was turned the short sharp shock waves from the hammer to 
long shock waves. Sort of what happens when you tap a bowl of Jell-O and 
it wobbles back and forth for a while.

What Tom recommended was that I get rid of the "squishy stuff" except 
for the high density pad, (so that I wouldn't beat the heck out of the 
concrete), and add 3" of solid steel plate to the bottom of the hammer base.

He also had some interesting comments about the relatives densities of 
concrete and steel.

The hammer is now moved, it is better just on the six inch concrete slab 
and rubber mat than on the first construct.

You might want to get someone who understands wave dynamics vs soil 
compaction, to help design this. Those longer rolling waves could get 
the same effect that earthquakes can produce, turning the otherwise 
solid ground all liquid for an instant.

Mike Graf


Peter Fels And Phoebe Palmer wrote:

> Following this line of thought ( that a cold shut absorbs energy).....I 
> have a situation that goes like this.
> We live on  top of  a very steep lump of clay with some rocks in it. The 
> land drops away on 3 sides of us steeper than the angle of repose. On 
> one side, we have a sheer scaling face that drops a couple of hundred 
> feet, next to it is a very steep slope that falls 750' to the ocean.
> Eventually I'll get my power hammer installed but i'm worried about 
> jiggling the clay under us too much when it's been soaked by the winter 
> rains. If we slide down the hill there is no reason to think we will end 
> up on top at the bottom....so...
> I've been giving a lot of thought  to the foundation to go under the 
> hammer, as you might imagine.
> My tentative plan is to dig deep and pour a couple of yards of 
> reinforced concrete, put in a layer of timbers topped with another yard 
> of concrete. On top of that I plan to stack alternating layers of 
> plywood, cork, steel, rubber,  4"wood slab and more timbers.
> The theory is that different layers of materials will tend to damp 
> different frequencys of vibration and the cold shut effect will be 
> compounded by having all those different layers.
> It's a lot of extra digging and trouble but I'm spooked about jiggling 
> majestically down the mountain side.
> Is my plan going to work? Any suggestions/opinions would be 
> appreciated......Thanks...Pete F
> 
> Mike Spencer wrote:
> 
>>> On the issue of force, basic physics dictates that force equals mass
>>> x acceleration.  So a heavy hammer at X velocity has greater force
>>> than a lighter hammer at the same speed.
>>>   
>>
>>
>> That's not quite right. A mass m at velocity v doesn't "have force".
>>
>> What it has is both momentum (M) and kinetic energy (KE).
>>
>>    M = m * v          # Momentun is mass times velocity
>>
>>   KE = 1/2 * m * v^2  # Kinetic energy is 1/2 of mass times velocity 
>> squared
>>
>> If you swing a small hammer faster, you increase the KE way more than
>> you do the M.  And you soon reach the point beyond which you can't
>> swing the hammer any faster.
>>
>> If you "get a bigger hammer", you increase M without having to swing
>> the hammer faster.
>>
>> I'm completely happy with the concept of conservation of energy
>> because KE can be converted into some other form of energy, say, heat.
>> F'rgzample, when you hammer a cold bar til it's hot, a bunch of your KE
>> is turning into heat.
>>
>> I'm having a bit of trouble with grasping conservation of momentum
>> because if there's no v, there's no M.  I see that momentum is
>> conserved with bouncy things (perfectly elastic things like steel
>> billiard balls or knocking a cold steel pin out of a bushing).  But if
>> I hit a piece of lead or clay with my hammer, the hammer stops dead in
>> its tracks, the clay or lead moves (mooshes) a bit and stops.  The KE
>> is presumably transformed into heat but, since noting is moving,
>> there's no momentum.  Huh.  I gotta re-read my physics book again
>> because I don't get it.
>>
>> On one of my MIT trips I had an opportunity to get a physics prof off
>> in a corner with paper and pencil and ask him to explain this.  He
>> gave a nice lucid explanation of how momentum is conserved in bouncy
>> things but kept changing the subject when I asked about hammering
>> (nearly) completely in-elastic stuff like clay or lead.  Huh.
>>
>> On a related note, I think (but can't prove) that the anvil doesn't
>> just "absorb" the energy of the blow (as charles said).  Some of the
>> energy is absorbed by the (presmably) hot iron and is converted into
>> heat.  I think that the rest travels through the anvil as a shockwave
>> and bounces (echoes) back against the workpiece while it's still in
>> contact with the hammer, thereby amplifying the blow. Cracks in the
>> anvil or joints between pieces of junk from which you've made an
>> anvil-substitute dissapate the energy of that shockwave and give you a
>> dead, less effective blow.
>>
>> - Mike
>>
>>  
>>
> 
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