How I built my Drawing Machine... a 3 pendulum harmonograph project. ArtGivingHope.org Dan Preece

My weekend project of building a 3 pendulum harmograph.
Full credits to: www.karlsims.c... for design and components etc:
Materials list
Lumber:
1 3/4" x 3'x3' plywood for table top
4 1½" x 1½" x 40" for legs (about 14' total)
4 1½" x 8" x 12" for leg braces (about 4' total)
4 3/4" x 4' dowels for pendulums and pen lifter (make sure they are straight)
1 3/4" x 1½" x 30" oak to cut for pendulum supports, and other
1 11" x 11" x 1/8" board for platform to hold paper
Hardware store:
3 3/4" x 5" long metal pipe nipples (plumbing section)
3 3/4" to 1" metal pipe bushings
3 1" steel clamps
4 1¼" x 4" metal plates (or 2 1¼" x 8" plates cut in half)
1 large metal washer with 2½" outer diameter, 1" inner diameter, for gimbal
1 screw-eye for pen lifter
various drill bits: 3" circular, 3/4", 1/8", etc.
various #10 screws (1", 1¼", 1½", 1¾", 2", 3")
a few thin nails
tools: drill, saw, hammer, tape measure, file, sand paper, etc.
Sporting goods store:
2½ lb weights with 1" hole, at least 8 of them
Art supplies store:
2 1/2" x 1/4" x 30" balsa (and maybe a spare or two)
various pens such as: Silver Uni-Ball GEL Impact, and Staedtler Triplus Rollerball
some string and rubber bands
paper, 8½" x 11" (or 9" x 12") some black, some white
Adjustments
Weight Height
Adjust a pendulum's weight height to change its swinging frequency. The frequency of a pendulum varies with the inverse of the square root of its length, so to swing twice as fast, the length between the fulcrum and its center-of-mass would need to be 1/4 of the original length (which may not be practical with this harmonograph). For a 3:2 or 4:3 frequency increase, one of the weights would be raised around 19" or 15" respectively, although you should probably do some timing tests to find and mark these heights experimentally.
Weight Amount
Add more weight to a pendulum to counteract friction and make the swinging last longer. I've found that 5 lb (2 x 2½) on the rotary pendulum, and 7½ lb (3 x 2½) on the other two works fairly well. Note that adding more weight does not generally change the frequency of the pendulum.
Phase and Amplitude
Each time you swing the pendulums to make a new drawing, the relative phases and amplitudes of each pendulum will vary. Try some where the rotary pendulum and the lateral pendulums are initially making circles in the same, or in opposite directions. Try some where the lateral pendulums are initially swinging in phase to make a diagonal line.
I spend my free time dreaming up ways to express my artistic side and to raising money for ArtGivingHope.org.
All of my pieces are sold or auctioned at ArtGivingHope.org and 100% of all earnings are used to fund the fight against diabetes that causes a large number of amputations, kidney failure and death in the Polynesions Islands of Tonga, Samoa and Fiji etc. As a foot and ankle surgeon, who has specialized in diabetic limb saving techniques, I am committed to aiding the Polynesian people who are in serious need. Starting in Jan, 2024 I will help fund and participate in medical/surgical missions to Tonga, Samoa and other countries, partnering with HopeForDiabetes.org. This organization is able to stretch every $1,000 donated into $10,000 worth of value in life and limb savings surgeries, wound care and preventative training for local doctors, nurses and community.
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