Stone forge vibration

[Krush]

I am looking for some input. I plan on making a large 3 station coal forge in my shop and I plan to use field stone for aesthetics however with my powerhammer pounding away I am concerned that the vibration may eventually crack all the mortar. I currently have my 100 pound air hammer sitting on 5 inches of firmly packed gravel and stone dust with a 1.5 inch industrial shotblast rubber liner acting as an isolator. Should I be concerned about the amount of vibration? I would hate to go to alot of effort to build a nice fieldstone forge then have a losing battle with mortar cracking on me.

 

any input is appreciated

[dablacksmith]

what is the soil like ? i dont think a 100lb hammer smacks the ground hard enuf to be a problem ... now if you had a 300 lb hammer it might ...i would not worry about this unless its real unstable ground ...good luck

[ThorsHammer82]

what's the floor? soil? gravel? concrete?

[LastRonin]

My $0.02 ... Build a small stone test structure where you plan to put the forge and see if it has issues from vibration by your hammer. That would unequivocally answer the question.

[Krush]

The soil is all clay under the 5 inches of stone dust, i could try the test unit but it may take a while to be able to see the effect. im probably being paranoid but i dont like doing things twice, i prefer to get it right the first time.

[VaughnT]

I think you'd have more issues with expansion and contraction through the seasons, than the vibrations of the hammer.  Field stone is notorious for "falling out" of the mortar, in my experience, because the mortar joints vary so much in thickness.  Most of the fallen stones I've seen were right a points where the mortar joint was less than a quarter-inch thick.  When the thin mortar cracks due to the freeze/thaw cycle, there strength of the joint is compromised and failure begins.  This is one of the few times I like to see whiskers in the mortar.....

[windancer]

My air hammer rocks everything in the shop. It sits on 6" of concrete and is welded to steel bolted to the floor with concrete anchors. The hammer foundation and the hammer are doing fine after several years.

But the vibrations knock things from the walls, from the anvil storage, the vice storage, the desk and from my tool racks.

I would NEVER build anything from stone or rock anywhere in my shop.

Dave

[ThorsHammer82]

Dave,

 

Part of the reason your hammer shakes the shop so bad is because of the concrete floor. It transfers vibration far better than gravel or soild does. I think in his situation it's really going to depend on how far from his hammer he wants to build his forge.

[VaughnT]

Dave, did you isolate the hammer's pad from the rest of the floor?  

[windancer]

No, same concrete everywhere in the shop. It varies between 5 and 9 inches in depth.

I did lay down 3 sheets of plywood with some caulking between them. The plywood extends about 18 inches on 3 sides of the hammer.

Dave

[LastRonin]

Dave,

How heavy is your hammer's anvil and base, and what is the tup weight?

[DSW]

An easy way to check vibration transfer would be a simple glass of water. Fill the glass and set it where your forge will go, then fire up the hammer and beat the snot out of something and see if you notice the vibrations in the water. It won't give you an acurate way to note exactly how much vibration there is, but it should tell you pretty quick if your floor is transfering the vibration from the hammer to the forge location. Small ripples probably aren't much to be worried about, but if th e water is sloshing out of the glass, you might want to rethink things a bit.

 

 

They used to judge how smooth train tracks were this way. They'd set out a full glass of water on a table in the rail car and see how much was left in the glass after they passed thru a track gangs section. The Pensylvania Railroad used to give an award to the track gang with the smoothest section of track this way IIRC.