You might want to look a some of the videos of the shops that made things like shovels and other garden tools.
They flattened stock by placing it between 2 constantly moving syncronized rollers.These rollers had large flats machined in them that allowed the operator to stick the hot steel between them once every revolution.Unlike rolling mills, the rollers were turning toward the operator and the work was pushed back toward him so there was little danger of being drawn into the machine.
I was impressed by how quickly the stock was transformed by this process.

Rollers are a whole different animal and do not require any sort of anvil. I was just sort of musing about a power hammer that would not need an anvil. If it were horizontally configured the scale would fall to the ground and not on the die as well.

Thanks Grant -It would seem that some "unyielding surface" is less unyielding than others. -grant

Yeah, I just wanted to look at one side, so assumed a constant for the struck surface.

I have a question for the experts; What is the consensus on built up anvils? I know stacked anvils are not ideal, what about verticaly oriented additions? Must they have 100% penetration welds to be truly effective? Sould I be thinking about adding a bunch of stock all around my anvil (and a hundred pounds or so of fluxcore) to improve efficiency next time I get powerhammer ambitions? Would it be effective to use enough weld for structural integrity only?

Total newbie here, I'd like to throw in the factor of the power source, and its application in the hammer design. I found that the gearmotor on my hydraulic powered rusty type hammer (see JYH and press thread in the next page) wasnt up to the task, when I went to a rotary piston motor it hit a lot harder. I think in addition to the "whip" action of the springs, there's also a fair bit of downward force from the motor to the hammer. The hyd motor is powered off pump on a 12hp diesel, I'd suppose I have around 8hp for my hammer motor.
My anvil totaled about 250 lbs, and the hammer is about 35 lbs. There's also the additional weight of the press framework, it's bolted into the slab through 2" of plywood. It dosnt move around when pounding, but I can sure feel the blows in the concrete, guess I'll see how the anchors hold up.
I think there's some aspect of the additional force applied to the tup, adding more to the blow than just the weight of the tup.

Built up anvils are fine. Think about my Bradly cushion helve hammer and many others. It has an anvil sitting on the base with a sow block sitting on top of that and a die on top of that all held together with wedges. That is held in front of the hammer frame with 4, 1 inch bolts with a wood cushion between the frame and anvil. Thats about as built up as you can get. If all the parts sit flat on each other good welds should be all you need. If you are going to put plates on the sides of the anvil think about what is trying to happen when the ram strikes the anvil, the plates on the sides will want to move up (if this correct and I believe it is ) try to design your addition with this in mind.

By the way my 40# Bradly anvil sow block and die weights 900#. Thats 22.5 to 1 and it is goooooooooood.

Built up anvils are fine. Think about my Bradly cushion helve hammer and many others. It has an anvil sitting on the base with a sow block sitting on top of that and a die on top of that all held together with wedges. That is held in front of the hammer frame with 4, 1 inch bolts with a wood cushion between the frame and anvil. Thats about as built up as you can get. If all the parts sit flat on each other good welds should be all you need. If you are going to put plates on the sides of the anvil think about what is trying to happen when the ram strikes the anvil, the plates on the sides will want to move up (if this correct and I believe it is ) try to design your addition with this in mind.

By the way my 40# Bradly anvil sow block and die weights 900#. Thats 22.5 to 1 and it is goooooooooood.

Sounds like full pen welds would be required for best effect then. I can take my anvil out of my hammer when I get a bunch more steel to weld to it.