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  • Looking for help - Power Hammer linkages [pic heavy]

    Discussion in 'The main mechanical design forum' started by leeknivek, Apr 8, 2015.

    1. leeknivek

      leeknivek New Member

      Apr 2015
      Likes Received:
      Hello! I'm having some design issues.

      I'm new here, obviously, but I am a blacksmith, among other things. I am not an engineer. I thought you fellows would probably enjoy this project I am doing - creating a mechanical power hammer - and might be willing to help me with some designs I'm playing around with in my head...

      For a little background:

      A blacksmith's power hammer has a special working principal that makes it so effective. It's relatively simple - a crank, a spring and toggle linkage, and a ram/hammer/tup. They connect in that order. What makes a "power" hammer different from any other - drop hammers (as the name says - uses gravity), trip hammers (uses toggles to amplify leverage while user pushes the hammer down by foot) - the power hammer's spring and toggle linkage allows the ram - the hammer - to have a variable stroke. This is important for working materials of various thickness, but, that's just the tip of the iceberg. A power hammer does not only use gravity to hit, but adds velocity, so that as the ram moves faster, the spring will compress more and give a "snap" to the ram, effectively giving more velocity to the static mass. Harder hits, move work done. (and these things will typically hit about 3 times a second).

      There are two "main" types of linkage. One is DuPont style, with many patent-evading offshoots, and the other is the spring-helve type.

      Here are some examples:

      DuPont hammer:

      DuPont linkage:

      Spring helve:


      As one may notice, the DuPont style (which is the majority of all hammers) is particularly tall, and also puts 50+lbs of spinning steel right in one's face (on the littlest ones...), while the Spring Helve style is shorter but has a larger footprint.

      Since I am building this myself, I'm trying to work within what is proven to work, while also adding a little flair. This is made mostly from scavenged materials (rule #1 of blacksmithing, it seems), but my local yard is plentiful. I have just about everything acquired and figured out except for the linkage. Now, these DIY hammers that many blacksmiths have made use a design known as the "Clay Spencer Tire Hammer":


      This is the route I'm going ... for the most part. I'm trying to figure something out that still works at least as well, but isn't 8 feet tall. The working principal is the same here - the big difference is that it has a spare tire donut for the crank and a friction drive from the electric motor. This makes for a pretty effective clutch mechanism.

      So the idea I have is to reverse the drive, put it upside down. Linkage and all. Now, from my basic understanding of mechanical design, this seemed to work at first but now I have my doubts. I'm wondering if it is possible to make such a linkage. Here's an animated .gif to illustrate what I've come up with:


      The little pink part is supposed to be the face of the ram. The ram and the "guide" part are connected laterally - hard to show in 2D using MS paint...

      This .gif sort of shows what "should" happen ... assuming this would even work. The end goal is to have the hammer not contact the anvil unless it happens through compressing of the spring. So that the toggle arms and links push together, allowing a taller geometry. I'm having a hard time coming up with a design that works the same way but with the crank in this position. I know I could use a flywheel above, have the drive come up from the ground but that sort of defeats the purpose for me.

      so ... I know, I know, "KISS". Maybe someone will humor me?

      Thank you very much for your time, sorry for the lengthy post! :D

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