String Chart From Greg Schreiber
"This is an example of a calculation spreadsheet I use for calculating optimal string gauging. The numbers that are most important are the tension number on each string and the total tension on the autoharp. For individual strings it's imperative to have enough tension that the string doesn't sound like spaghetti, and not so much that it becomes a steel rod that won't vibrate. For total tension on the autoharp, too much tension can cause the body of the instrument to self destruct."
RBI Standard Chromaharp - String design parameters in a single chart
Several String Charts From Bob Lewis
"The reader should understand that this may not be exactly like a packaged set and that George Orthey used a couple variations in the bass note array. This is specifically for an Orthey favoring CGDA as a matter of interest or reference for the same approach.
"George also used one with a low A and no wound A#. Another one starts on low G, all aimed at string band keys, the sharps rather than flats. Greg and I (and Tom) have libraries of schedules for all sorts of set ups and brands/models of autoharps and can devise new schedules as needed. This one is an example.
"That list of frequencies is a segment of the program that allows notes to be referred to by name, while the calculations rely on the frequency number.
"Indication of a good progression of string sizes across the array is the smoothness of the FEEL chart. Feel is a function of tension, so the tension chart is less important, while highlighting anything over the working limit of 60 pounds. The overall tension shown as a summary of the calculations is important to compare to the proven total in a factory chromatic schedule of just under 1800 pounds.
"Stress could better be expressed as % break length, while I just watch that the number does not exceed 250k by much, the stress calc for note and position at the top end known to be on the edge of what breaks easily, for example going from 36C up to 36D and pow!. The vibrating length on a 37th string will allow that D note handily."
Orthey CGDA charts - Charts related to stress, tension, break length percentage, etc.
