how does the anvil work?

[Keganthewhale]

So after looking at a number of threads and reading through more pages and posts than i can count i've decided to ask the question! how does the anvil work on home made power hammers? everyone says that solid is better, of this i have no doubt, but my question is more specifically how does the blow transfer and reverberate through that material? for instance, in the helve/krusty/rusty style of hammer everyone wishes they could their hands on a rail-car axle due to its substantial girth and solid weight, so its easy to see how the force from the tup would travel straight into the piece that you are working on and down into the anvil. But now imagine the three following anvils, the 6”x36” square tube filled with sand and topped with a heavy plate, the 6”x36”square tube filled with lead (and for the sake of the example lets say stacked blocks that you somehow had the time to acquire that much lead and cast it into bricks that are close to the inside tube size so in essence its solid) topped with a heavy plate, and the last filled with 1/2”x36” square bars topped with a heavy plate. So now we have three identical in appearance anvils for a power hammer, which one works best and why?

 

Now how would that same energy transfer if instead of it being a pillar it was a slice of a pyramid with each prospective filler:

 

                llllll

            llllllllllllllll

         lllllllllllllllllllllllll

      llllllllllllllllllllllllllllllllll

   llllllllllllllllllllllllllllllllllllllllll

  llllllllllllllllllllllllllllllllllllllllllllllll

llllllllllllllllllllllllllllllllllllllllllllllllllllll

 

would it transfer the same? Is it just the mass that dictates how efficient it is?

I'm curious as to what everyones thoughts are on the matter.

[jeremy k]

Any anvil made for treadle hammers or power hammers that are a tube and filled with whatever......loose that idea - they are not good - solid steel is the only answer. There is no way a "filled" tube will act as a solid mass. Sorry. Get a solid mass.

[njanvilman]

Add up the time and money spent on acquiring that much lead, you could have bought a solid bar of steel.  The only 'hollow' tube that might work is a very heavy wall tubing, such as a 6" OD with a 2" ID. Unless you can find a scrap piece or buy a drop, the solid bar will be cheaper.

Edited March 3, 2015 by njanvilman
Spelling

[Keganthewhale]

i'm not building one! its just strange to me that the idea is thrown around (and it might have been sand in other parts of the hammer as a whole just to add weight)  and i am seriously just intrigued as to how that energy transfers, and how the shape of the anvil affects it efficiency. just like how you don't do the majority of your forging an inch in from the hardy hole on a london pattern, because the mass isn't directly beneath where your hammer falls and that makes it less efficient.

[jeremy k]

You answered your own question - because the mass isn't directly beneath where your hammer falls and that makes it less efficient.

[Keganthewhale]

so then the only reason to have any solid shape other than a pillar is strictly to have enough mass to keep the hammer from moving? it doesn't help in any other way?

[ThomasPowers]

please read a basic physics text on how inertia, mass and  elastic and inelastic collisions work;  pretty much the same since Sir Isaac started the ball rolling so to speak.

[patrick]

The reason the tubes filled with objects approach is less desirable than a solid block has to due with the fact that those loose objects will not move with the housing when the ram contacts the anvil. Since objects at rest tend t stay at rest when impacted, the mass resisting the force of the ram must move as a single unit. If not, then the filler material will stay at rest  while the housing moves. This is the exact same thing that happens when you accelerate rapidly while travelling in a car. You (the filler material) tend to stay at rest while the car (anvil tube) accelerates. The result of this is that you are forced back into your seat during the acceleration stage of travel. In the world of hammers, efficiency is all about resisting the forced exerted by the ram and transfering that motion into the work piece. That is accomplished by the anvil which needs to be large enough to resist moving. Chambersburg Engineering published data showing that maximum efficiency was reached when the anvil wieghed 20x the ram. That was for steam hammers doing industrial work with industrial foundations. For a Rusty style hammer, you may find that the maximum efficiency is reached with a different (likely lower) ratio due to other losses of efficiency within the system.

[b4utoo]

Just curious. If the tube was filled with some type of iron and cement mix. Would this make the tube a solid, and act as a anvil. Consider you have a thick top steel plate to take the initial blow?

[Frosty]

Loose material in the anvil basically prolongs the impact, lowering the G load so less energy is transferred to the work. This is exactly what the padding in a helmet or the air bags in a vehicle do in a collision.

B4: No it won't improve the situation enough to make a difference. The difference in resonant frequency CAN be a good thing, it's what makes Fisher anvils so much more quiet. However the resonant frequency of concrete is nonexistent so the energy passing through the anvil is just absorbed and dissipated in the concrete. For the intents of the velocity of the shock wave generated by a hammer on an anvil it's an airbag and actually reduces the anvil's efficiency.

Just heavy isn't the answer, any more than just being old makes a thing an antique. Some things are just heavy or old or both with no added value.

Frosty The Lucky.

[Ed_Steinkirchner]

well that makes me think though, say you had a bunch of 1'' thick plate, 8'' wide on hand, cut those to the correct length and stacked 8 of them, then welded the edges together before putting the actual die mounting plate on the top. Would that work as though it was a solid 8x8 block of steel?

because then there is no parts moving around to absorb or dissipate the force being put into them, same question goes for a stack of, say 40 ea. 1'' plate discs 9'' in diameter stacked and welded into a large block

just tossing that possibility out there

[Quarry Dog]

Unless the welds are full penetration, there will always be a gap between the plates. This would make them one solid block anyway, although with messier grain and possible inclusions/porosity.

 If you did just weld around some plates, after the initial hit on your workpiece, the top plate would flex, dissipating energy, until it hit the next plate, and so on, until there was no more energy left to work with.  This is much like why even a tighly packed deadblow hammer doesn't rebound hardly at all.  I'm sure that what actually happens is way more complicated than that, but that's the basic Idea of it.

  The only exception I can think of would be if the plates were all precision ground and sweated together like gauge blocks before being welded all around while somehow preventing warpage, which would unsweat the blocks and cause air pockets.  Even if you could manage that, a feat in itself, I believe that it would still find some way to dampen your blows more than a solid block, and probably cost 100 times as much.

All of that being said, It would definitlely be better than banging on a single piece of 1" plate, unless the stack is made of cast iron, in which case you'll have a fun time not making it crack while welding, and then not cracking it when you hit it.

Edited April 24, 2015 by Quarry Dog

[Dogsoldat]

Depending on whats doing the hitting the plates will still flex and vibrate.  Same principal as why it is not recommended to arc weld a face plate on an anvil only around the edges.   At least that's  my understanding of things.

[VaughnT]

Another way of considering things.....   Cement has been around since the Romans a few thousand years ago.  Considering how much cheaper and easier it would have been to fill a metal shell with some cement or epoxy, the fact that all these big businesses didn't do it should be rather telling.  If it was a good idea, hammer and press manufacturers would have been doing it for ages.

Sure, you can weld up a bunch of plates.  And, it would be a better anvil than a cylinder filled with cement.  But not by much and wholly dependent on the quality of your welds and the gaps between the plates.  A stack of plates on end would be a better solution than a stack laid up like some flapjacks.

[turbo7]

Do a simple experiment: get a block of concrete, a block of wood, some steel plates clamped together, and a solid block of steel, a bag of sand,all similar size just for the sake of it, then take to each with a hammer for 10 min and the results should tell us something? 

[brian robertson]

well that makes me think though, say you had a bunch of 1'' thick plate, 8'' wide on hand, cut those to the correct length and stacked 8 of them, then welded the edges together before putting the actual die mounting plate on the top. Would that work as though it was a solid 8x8 block of steel?

because then there is no parts moving around to absorb or dissipate the force being put into them, same question goes for a stack of, say 40 ea. 1'' plate discs 9'' in diameter stacked and welded into a large block

just tossing that possibility out there

​John Larson would the one to ask