Hammer Flight

A Hammer Blow: 490ms...

(See this image enlarged - 127k)


Hammer flight study underway and planned

Peter Dourmashkin (of MIT's Integrated Studies Program) and I have worked on an investigation of the physics of hammering intended as a heuristic for physics education. With the generous assistance of MIT's Edgerton Center , we've been able to record hammering on digital video at 1 millisecond intervals. This allows us to track the flight of the hammerhead, determine velocity, acceleration etc. for the hammer and track the body movement of the smith.

We had hoped that we would be able to use a hammer with an integral strain gauge attached to a recording device so that impact dynamics could be tracked precisely. The impact event takes place in so short a time that even 1 ms is much too long an interval to calculate final velocity or kinetic energy from (x,y) differences between video frames with acceptable error. The gauged hammer available turns out not to be suitable for such heavy blows. Instead, we've moved the camera in close to the impact point and shot at about 6,000 frames/sec.

A preliminary trial indicates that this will give us a reasonably precise value for contact time under load when hammering on a plastic material. Because the visible radiation from hot iron causes too much glare for the camera, we used a lead bar at room temperature as a model for hot iron.

These images haven't been worked up fr inclusion here yet. Real Soon Now...

For a quite elastic material (a cold steel plate) it looks like the contact time is at most a third of a millisecond with the entire period of contact occurring between frames. We should be able to get good values for velocity before and after impact and an upper bound for contact time.

As this page develops, we'll be adding data lists of hammer position, calculated velocity (example, 7k), acceleration and kinetic energy, error estimates, images tracking the hammer flightpath (example,ca. 16k) and whatever else we think of.

I hope that we can also add some material on the cognitive and neuromuscular components of hammering.

Stay tuned...

If you got to this document directly, you may want to go to my home page.

Thanks to Steve Kim (stevek@mit.edu) and Tony Caloggero (Edgerton Center Staff) for assistance and Prof. Sam Allen for use of the blacksmith facilities.
Updated 9 May 2000 -- Mike Spencer