The Harmonic Fire Pendula was Attoparsec's first large-scale art installation, built for Burning Man 2012.
The HFP consists of 16 flaming pendula, suspended from a 15 foot tall, 20 foot long structure. These are of carefully calulcated different lengths, such that their periods are tuned to be in a harmonic relationship with each other. In a given period of time, the longest pendulum will swing n times, the next longest will swing n+1 etc. This results in some really stunning wave patterns being created when viewed down the length of the structure.
The project started with a 1/3 scale prototype. This was used to develop the release mechanism and experiment with different pendulum/weight designs. The release mechanism was of particular concern -- the final design allows each pendulum to be pushed up independently and "cocked" into place. When all are ready, a lever is pulled which slides a rod along the top of the main beam. This trips the 16 release latches, dropping the pendula simultaneously. Details of this can be seen in the videos below.
The dynamics of the system were explored with this Java applet. You can tweak the target pattern length in seconds and the number of oscillations the longest pendulum should make in that time. It assumes the pendulum rods are made from 1" square steel tube with 1/8" wall and adds a 13 pound weight at the end to roughly match the physical configuration of the real device. The pendula lengths necessary to achieve the target parameters are printed to stdout, if you're interested. It assume 0.8 pounds of kerosene burn off of the tip over a 5 minute run, and the periods of the pendula are shifted by 1% up and down to test real world variances. The (ugly, ugly) code is here.
Basic design rendering: HarmonicFirePendula_design2.png
1/3 scale prototype: HarmonicFirePendula_prototype1.jpg
V.1 release mechanism test: HarmonicFirePendula_prototype3.jpg
This project was made possible due to a grant from Burning Man and the support of our many Kickstarter backers.
Assembly and operation of the final article:
The original inspiration:
1/3 scale prototype full fire test:
1/3 scale prototype:
Improved release mechanism:
July construction update:
Mid-August constriction update: