Patent 4,199,867

At first glance, this appears to be just another version of an oscillating table type of drawing machine; but it isn’t that at all.  This is actually a cleverly designed Twin-elliptic Pendulum Harmonograph!  The table is rigged so as to prevent twisting motion and note the deflector pendulum mounted below the table.  The rigging serves to replace the more usual pendulum rod so the entire apparatus can be compactly stored.  

Mr. Cass, the inventor, obviously gave a great deal of thought and study to the Harmonograph. The many beautiful drawings (harmonograms) which were submitted with his patent are indicative of the wide range of Lissajois curves one can generate by carefully tuning a Twin-elliptic Pendulum to a desired harmonic frequency.  Especially instructive is the chart on page 10 of the patent, which specifies some useful frequency settings for producing harmonic vibration figures. 

This drawing machine would make an excellent science fair or hobby project. I have never seen this design of Harmonograph in operation, but it looks good on paper and the submitted drawings are proof that it works! 

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