I was wondering if anyone though that a couple hundred pound concrete
"pillar" with an inch or two of steel on top (welded/bolted to the
internal rebar structure of the pillar) would provide reasonable
service for a treadle hammer? Or would we quickly be dealing with a
pile of gravel? I was thinking something like an 8"x8"x36".
As described you will quickly fracture the concrete. You would need some
kind of shock absorber between the steel and concrete. I don't know if
this would work well as an anvil or not.
My friend was quite amazed at the damage his treadle hammer did to his
concrete driveway in a short time--no pad underneath.
Is concrete+labor that much cheaper than steel? Admitedly, steel has
gone up a fair bit.
The question was partly practical, partly theoretical. I agree that in
the end steel is probably the way to go, but concrete is also a bit
more convenient to obtain and could offer some flexibility in design if
it would hold together. It's also easier to sneak past my wife.
You're gonna need a shock absorber or you'll have gravel right quick.
This might work..... take a couple of pipes and cast them into the
concrete vertically. These are the cylinder of your shocks. Thicken up
your top plate to at least three inches and weld two more pipes to the
bottom that will fit inside the pipes you cast into the concrete, so
there's a sliding fit. There should be at least a foot of 'overlap' in
the pipe joint for positional stability. Go to the truck stop and get a
couple of Rubber, not plastic, mudflaps and cut them up to fit flat
between the top of the concrete and the bottom of the top plate. Weld on
a sheetmetal skirt to the sides of the top plate to reach down over the
mudflap stack to shield it from splatter and radiant heat. Wait for
everything to set up, go to work. Consider the mudflap an expendable
component over time.
Concrete cracking aside, wouldn't inserting a shock absorber into the
anvil pretty much defeat the purpose of the anvil mass? I would think
that a wooden anvil or hollow steel tube could be just as effective in
this case. Are "mass" and "compressability" two different
I would say absolutely. You are looking for something with enough mass to
barely notice the impact of the hammer and hard enough that it wont absorb
shock but return it. I'm sure my physics teacher would be groaning about
now but that's the idea... ;-)
Mudflap is pretty stiff rubber, about the same compressibility as a tire
tread. The idea is to absorb the impact shockwave, the 'ring' if you
will. I have a treadle hammer, the head weighs about 200 pounds. It used
to drive the anvil down through the 'stump' made of two by fours and angle
iron. then I put a piece of mudflap under the anvil and it solved the
problem. The anvil deflects down less than 1/16" under an 'everything I've
got on the pedal' stroke. What was happening was the impact shockwave was
reflecting off the concrete floor and expending its rebound in moving the
outer layers of two bys in the stump up around the anvil. Once I changed
the 'sound' transmission characteristics just a bit, the wave stopped
propagating. It's the shockwave that powders the concrete. If you're
leary of elastomers, try a soft metal, like lead. You'll still have the
give in the system that will change the shockwave characteristics at the
base of the anvil. As for the anvil actually moving, it's a case of mass
versus momentum; the same formula that tells you how hard the rifle is
going to kick, so more mass is better. The anvil should weigh at least as
much as the hammer head. Steel weighs 7.9 grams per cubic centimeter; 2.54
centimeters to the inch, 454 grams to the pound. Kinetic energy(impact
force) = mass (in pounds) X velocity squared (in feet per second) / impact
area (in square inches) yeilding an answer in foot pound seconds per
square inch. Get the impact area small enough and you can generate enough
energy to make an impact fusion in your work, even cold. Clear as mud,
My main treadle hammer has been sitting on the shop floor for 15 years
or so and hasn't done any damage to the concrete. The concrete is 6
inch thick, 4500 psi and reinforced with rebar. I have no pad between
the floor and the teadle hammer. I think the problem with one poster's
driveway is that, if you don't ask, you will get 3000 psi concrete and,
of course, its' usually only about 3 1/2" thick. Just for reference, I
also have a 50 pound Little Giant sitting on the same shop floor. It
has been there since 1987. That one sits on a 1/2" think rubber pad
(used conveyor belting) and has not damaged the floor either. I glued
the pad to the floor with silicon seal and then glued the hammer to the
pad with the same stuff. No bolts at all. It hasn't moved.
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