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Much of today was devoted to preparing some more words for the web site, measurement, sketching, studying catalogs, calculations, inventorying cleaning, recycling machine shop scraps, ordering more steel from two different suppliers, banking, etc. I did do some machining. Just one of those nickel and dime days I have to go through to get to the funner days ahead. So I have no shop adventure story. But you might find the following interesting.
Ric Furrer asked an interesting question today over at the power hammer section of IFI asking about utility hammer sizes and their requirements for air flow and pressure. Grant Sarver spoke of leakage in the older hammers converted from steam. They're talking about the big old machines, not the new little ones. Grant did suggest 25 cfm per 100 pounds of tup.
Here is how I think about air requirements for little utility air hammers. I don't claim to be an expert. My hammers do work well.
Utility hammers' air power requirements are mostly based upon raising the tup a given number of times per minute and then the air available is more than enough for lowering the tup forcefully into the hot metal being worked. Gravity works with the descent and against the ascent. Any machine I build will run at about four blows per second at full treadle and unless adjusted otherwise will tend to use a 3" to 4" stroke (inertia can lengthen this). If I lengthen this stroke 50% via my stroke tuner the air flow required rises by 50%, and reciprocation speed is reduced. And I find the 100 pound hammer runs well with a 7 1/2 hp 2 stage Quincy piston-type air compressor. That is my empirical base line and is likely to be very near Grant's suggestion of 25 cfm per 100 pounds of tup. This machine runs fine at 80 psi, but 100 psi is nicer, and 125 psi is pure luxury (above that accomplishes almost nothing). It uses a 3.25" bore cylinder and a 1" diameter cylinder rod. The area of the piston raising the tup is .2227*(3.25*3.25 - 1*1) = 7.5 square inches. That's 7.5 square inches per 100 pounds, or .075 square inches per pound. When that area per pound is raised to .1 my hammers become very snappy in the 80 to 120 psi pressure zone. The Octagon 75 and 125 are two such machines. If the cylinder ports become smaller some of this snappiness disappears. Higher pressure will not overcome a restrictive port size because of turbulence. The only cure is bigger ports, or slower running. I suspect that is the primary reason huge machines ran so slow compared to medium and small machines.
Hence, my approach is pretty much empirical, and so long as the port issue is finessed the scaling up or down of hammers works for me. It might work with huge hammers, but I have no evidence.
Ric Furrer asked an interesting question today over at the power hammer section of IFI asking about utility hammer sizes and their requirements for air flow and pressure. Grant Sarver spoke of leakage in the older hammers converted from steam. They're talking about the big old machines, not the new little ones. Grant did suggest 25 cfm per 100 pounds of tup.
Here is how I think about air requirements for little utility air hammers. I don't claim to be an expert. My hammers do work well.
Utility hammers' air power requirements are mostly based upon raising the tup a given number of times per minute and then the air available is more than enough for lowering the tup forcefully into the hot metal being worked. Gravity works with the descent and against the ascent. Any machine I build will run at about four blows per second at full treadle and unless adjusted otherwise will tend to use a 3" to 4" stroke (inertia can lengthen this). If I lengthen this stroke 50% via my stroke tuner the air flow required rises by 50%, and reciprocation speed is reduced. And I find the 100 pound hammer runs well with a 7 1/2 hp 2 stage Quincy piston-type air compressor. That is my empirical base line and is likely to be very near Grant's suggestion of 25 cfm per 100 pounds of tup. This machine runs fine at 80 psi, but 100 psi is nicer, and 125 psi is pure luxury (above that accomplishes almost nothing). It uses a 3.25" bore cylinder and a 1" diameter cylinder rod. The area of the piston raising the tup is .2227*(3.25*3.25 - 1*1) = 7.5 square inches. That's 7.5 square inches per 100 pounds, or .075 square inches per pound. When that area per pound is raised to .1 my hammers become very snappy in the 80 to 120 psi pressure zone. The Octagon 75 and 125 are two such machines. If the cylinder ports become smaller some of this snappiness disappears. Higher pressure will not overcome a restrictive port size because of turbulence. The only cure is bigger ports, or slower running. I suspect that is the primary reason huge machines ran so slow compared to medium and small machines.
Hence, my approach is pretty much empirical, and so long as the port issue is finessed the scaling up or down of hammers works for me. It might work with huge hammers, but I have no evidence.
