Cycloid Generating Program by Richard Thomas

Program Overview

Note: I received one report of malware on this program. However, no one else who uses the program reported any problems. I subsequently had it checked by Norton with no problems and the file was sent to Avast staff. A clean report was sent to me.

Download program here.

What the program does

This program is designed to print template outlines for Violins,  violas, and celli. The cross arches created are based on Curtate Cycloid curves. The shape of each of the cross arches can be independently altered by changing the “shape factor” entered in Column 7. A shape factor of 1 will result in a normal Curtate cycloid curve. A shape factor greater than 1 will decrease the upward concavity of the curve near the ends, while a shape factor less than 1 will increase this upward concavity. Neither the height or width of the curves are changed by changes in the shape factor. The program will create a long arch as well as cross arches. The long arch heights are taken from the cross arch heights entered in boxes in Column 2. The long arch is printed in two sections on a single 8 ½ X 11 sheet of paper. Cross arches for a cello can be obtained by using the half arch mode, i.e., two sets of half arches can be printed and joined to form the complete cross arch.  A normal cello long arch will be printed in four sections on a single sheet of 8 ½ X 11 paper. An additional extension of each section that overlaps the next section is printed to aid in joining the sections. Also an index mark is printed on the baseline at the end of each section which marks the joining points. On the home page of the program are boxes, in which, the data that defines the cross arches are entered. The data are entered as follows:

Column 1 - Position of arch measured from fluting minimum at bottom of lower bout.
Column 2 - Maximum arch height measured from the bottom of  plate (not from fluting minima)
Column 3 - Width of the arch measured from fluting minima at each edge.
Column 4 - Edge width from fluting mimima to outside edge.
Column 5 - Rise from fluting minima to edge.
Column 6 - Edge thickness at fluting minimum.
Column 7 - Shape factor which determines the degree of upward concavity near the minima
(All data entered in mm)

The program obtains the height of the printed cross arches by subtracting the edge thickness (Column 6 ) from the arching height (Column 2).

Long Arch Forms

The position and height data are used to create a template for the long arch. The long arch curve is created by joining all the cross arch height points with a cubic spline curve. However, the sections between the ends and the lower and upper bout cross arches are created using a section of a Curtate Cycloid curve. Similar to the cross arches, the cycloid sections of the long arch are modified by two shape factors (one at each end), as described above. In addition to the shape factors, The slope of the long arch can be altered at the position of the upper bout and the lower bout. These points are where Curtate Cycloids of the end sections joint the cubic spline sections. The slopes are adjusted by trial and error to give the smoothest transitions between the two types of curves.

Provision for Extra Arch

Normally only 5 arching templates are used to specify the violin arching. However, it has been suggested that having an additional arch might be useful in some instances. For this reason the program provides a way to insert an additional cross arch if desired. The arch can be placed at any position along the long arch. To insert or remove the extra arch click on the "Options/Extra Arch" menu. This brings up a dialog box in which the data for the extra arch are entered. The arch is then inserted by clicking the "Insert Arch" button. To remove the extra arch click the "Remove Extra Arch" button. When the extra arch is inserted the extra arch data boxes are placed on the home page. They are removed when the "Remove Extra Arch button" is clicked. However, the data for the extra arch will remain in the extra arch dialog box until it is changed. The extra arch data will also be saved when the program is closed. If you have the extra arch inserted when the program is closed, it will be inserted when the program is opened again.

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