[TheForge] more on hammer vibration and noise

Tue Oct 21 16:57:01 2003

I saw (heard?) a very convincing demonstration of this effect, though
perhaps more with regard to noise than vibrations of lower frequency.

Bob Bergman demonstrated the KA-75 hammer at CanIron I.  It was LOUD. 
About a year or so later he demoed it at Gichner's Hammer in (at Iron
Age Antiques).  It was so quiet you could have set it up in a garage six
feet from the neighbor's kitchen, with no complaints.  What changed?  A
~4" slab of steel under it in the second demonstration.  Must have been
about 350# or so.

Now, following up on that, cast iron is reliably reputed (Mark's
Manual, and other sources) to have the best vibration damping
characteristics of any metal.  (Or is that, 'of any material'?  Anyone
know?)  Would that be a better choice than steel in the present case
(assuming equal cost and availablity)?

Bruce
NJ

>>> [email protected] 10/21/2003 12:59:27 PM >>>

> Subject: Re: [TheForge] Re: stack o' plates vs, slab o' steel
> From: Andrew Vida <[email protected]>
I don't know about this.  Every manufacturer's foundation
> plan I have ever seen (that would be two, one for Chambersburg
> and one for Nazel) requires wood on a concrete block.  Steel
> against comparatively brittle cast iron is almost certainly a
> recipe for eventual structural failure of some form and degree.
> Don't place your hammer on a rigid surface, you will probably
> live to regret it.  Railroad ties sistered up and two to three
> courses thick should do very nicely atop a concrete foundation,
> all sunk to floor level.

Dear Andrew,

You may have come into this thread late, so I will try to explain how
we got
here.

A list member was inquiring how to best protect his hillside abode from
the
deleterious effects of power hammer vibration. The "standard"
foundation as
you describe is indeed flexible, but it transmits a great deal of
vibration
to the surrounding earth, with resulting noise, and dishes falling off
the
shelves in the kitchen next door, especially in the case of a hammer
with a
small, separate anvil.

When those hammer foundation specifications were drawn up, big, thick,
cheap
plates of steel didn't exist, and noise and vibration were not a big
concern
in a huge railway shop or factory, even if the hammer shook the whole
town,
nobody cared because they had jobs.

Here we are in the 21st century, with artist-blacksmiths running
smallish
power hammers in their garages (just 15 feet from the neighbor's
kitchen) or
on top of hillsides overlooking the ocean. What we need are "stealth"
hammer
installations that do not infringe upon those around us, or require us
to
excavate the floor in a rented garage.

What I have done very successfully in a number of cases is to recommend
or
provide a VERY thick, heavy steel plate for the hammer to rest on,
which
very effectively dampens the vibration of the anvil to the point where
it is
no longer a problem. In the previous cases, the hammers themselves
were
steel, so they were just bolted directly to the extra plate.

In the case where the hammer was being operated on top of a concrete
slab,
such as a residential garage, or patio, I recommend a layer of soft
Poron
(TM) foam between the extra plate and the floor. The addition of extra
mass
and the isolation of the foam solve the problem completely. Silent
hammer,
intact dishes, happy spouse and neighbors, mission accomplished.

In the case of a cast-iron hammer, one would obviously need to put
some
foam, leather, or other kind of gasket between the castings and the
extra
plate, to allow for irregularities in the shape of the casting, but
the
whole point is to firmly and effectively couple mass to the anvil which
is
the source of the vibration in the first place, and I still feel that
thick
steel accomplishes this with the minimum amount of effort, and it is
"portable". The gasket need not be very thick to prevent fracture of
the
castings, and still allow effective coupling. I have also used molten
babbit
metal, and even molten sulfur as a bedding compound to mount irregular
castings to a solid foundation, thereby distributing the load evenly
over
the bottom surface of the casting. Nowadays one could use epoxy, same
idea.

Even if you were to insist to put your railroad ties, etc, on top of
the
steel plate, I feel the steel would still  be a more effective
vibration
dampener than a big blob of concrete, but it works even better if it
is
firmly attached to the anvil.

A small power hammer bolted to a THICK steel plate, and sitting on a
couple
of squares of foam needs no further anchoring, and no further
foundation
whatsoever. the point is to make the hammer "assembly" so darned
massive
that for all intents and purposes it just sits there... even in
operation,
and the ground, neighbors, etc. are not affected by it.

I hope this makes sense.

Tom Troszak 

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