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Helve Hammer |
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Click on any photo for more Copyright 2002-2006 www.fergusonsculpture.com |
I have found that my wrist
and arm will not take a great deal of hammering before I start to
develop a pain that can last for months. So I decided that I needed a power hammer to do some of that hammering for me, and save my wrist and arm for other purposes. I still do some hammering by hand, mostly for finish work, but now I have mechanized the rough work.  The hammer is operated by an old air drill, which drives an eccentric, which drives a turnbuckle, which drives a leaf spring, which drives the arm, to which the hammer head is bolted. This is a relatively small helve hammer, the smallest that I have seen, and is a benchtop unit, approximately 30 inches by 24 inches. Rather than buy an air throttling foot control, I made a cable control foot pedal, using a bicycle shift cable. The cable operates a lever, which operates the trigger on the drill. You can see the lever in the photo, the cable and return spring are not shown. I now can operate the air drill at any desired speed, including making a single hammer blow.  A few statistics: The air drill is an old Sioux brand 1/2 inch drill, 375 rpm rated, but it operates more slowly in this application. The length of the arm is 18 inches, from the center of the pivot to the center of the hammer head. The eccentric has a 0.5 inch offset, with an overall travel of 1 inch, top to bottom. At low speed, the hammer head moves up and down about 5 inches. At high speed, taking advantage of the spring and the resonance of the arm and the spring, the travel can be 9 inches or more, which is what gives it the power it needs. The hammer head weighs about 2 pounds, and is made of 1.5 inch diameter steel rod, with screw-on heads for different purposes. The baseplate is 1/4 inch plate. The unit has more than 125 pounds of steel plate for weight to keep it from moving around too much. I started with about 50 pounds of plate, but that was nowhere near enough.  One of the ways to use a helve hammer is with a "rubber anvil". If you put a sheet of thick rubber on the baseplate, and then use a steel hammer with a dome face to hit the sheet metal, the hammer presses down in the center, and the rubber presses back, stretching and doming the sheet metal. In the photo above, on the left hand side, you can see the stack of steel plate for weight, and then the six inch by six inch by one inch thick rubber (70 durometer), glued to a plate bolted on top of the stack of steel plates. I have been very pleased with the ability of the hammer to work sheet metal using the rubber anvil. Learnings to date: I started with 50 pounds of weight on the baseplate, which was not nearly enough, the baseplate was jumping into the air! 125 pounds worked a lot better. I started with a wood arm, 1.5 by 1.5 inch, which broke in the first 15 minutes, so I made a new arm of 2.5 by 1.5 inches, and has held up so far. This hammer is based on other helve hammers, and I want to thank all the people who shared their knowledge and opinions with me. I could not and would not have built this hammer without their help. Many of the people who shared information with me did so by internet, and I have never seen them face to face! Thanks to everybody for their help. Richard Ferguson February 27, 2004 Click here for an article on The Helve Hammer -Theory, Tuning and Practice |
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