Ture Bergstrøm

Technical drawings of musical instruments

on the Internet

 This article was first published in FoMRHI Quarterly, January 1999

English translation: Oliver Rigby Hirsh

Full text version

Drawing instruments on computer

Recent developments in IT have among other things led to doing nearly all technical drawing, workshop drawing etc. on computer. This has obvious advantages, especially on account of the capability to edit drawings and to print them on paper in the required number of copies.

With regard to musical instruments, drawings generated on computer are no more nor less accurate than drawings done by hand. Measuring an instrument, one is obliged to make note of a limited number of measurements between a limited number of measuring points. The curves or surfaces that lie between these measuring points can be indicated on a sketch or at best be preserved on a photo, but they defy unequivocal description. When turning his sketch into a fair copy, whether by hand or on the screen, one tries to connect the well-defined measuring points with curves that "as best as possible" correspond with the appearance of the instrument, as he remembers it. These connecting curves are therefore subject to a certain degree of chance. A computer drawing gives the impression of greater accuracy than it in reality possesses, because distances between completely arbitrary points on the drawing can be measured with the precision of multiple decimal points. One must realize that the measuring points comprise the primary data (however much also they are subject to inaccuracies), and that the curves connecting them represent the interpretation of the draughtsman.

Keeping this reservation in mind, I believe that the computer is very well suited to the production of instrument drawings. For example, besides normal editing of drawings, scaling of an instrument to a particular size is quite a simple process; and when the possibility is added of quick and cheap transmission of drawings by Internet, which the recipient thereafter can edit and print as needed, it amazes me that there are not more instrument drawings available in electronic form.

In connection with a drawing of a recorder in the Museum of Musical Instruments in Copenhagen (Musikhistorisk Museum), I had the opportunity to work with a model for instrument drawings on Internet; in the following I will submit some reflections on choice of software for such purposes.

 

Demands on the program

Low price

One reason why drawing by computer is not more in use among instrument builders is presumably that the price for the recognized drawing program AutoCAD is so high (approaching £ 3500), that no craftsman can afford to acquire the program by lawful means. The AutoCAD LT version (price about £ 730) has not until recently been able to handle soft curves (see below). 

Userfriendliness

Most instrument builders would only occasionally need to work with instrument drawings; it is therefore important that the program does not use commands or function keys which must be learned by heart. Keying in coordinates must be easy and logical, since the conversion of measure-data to a drawing would continually necessitate marking out points determined by coordinates.

Soft curves

Very few of an instruments curves can be described in terms of straight lines and circles. The program must at least be able to handle elliptical arches, splines (= a figure which connects given points with a soft curve corresponding to a springy band fastened to the points) and Bézier-curves (defined by the two end-points and the tangent-direction of the curve in the end-points).

 

 Import of text

The program must be able to in import texts and graphs that are edited in normal wordprocessing programs, for ex. via the clipboard-function in Windows.

Drawing according to photo

In some drawing jobs it can be a great advantage to be able to draw after the contours of a scanned or digitalized photo. Therefore the program should be able to import commonly used graphic formats, as for ex. bmp or tif

Printing and plotting

Many will need work drawings on paper in full scale. Only very rarely would instrument builders have access to a plotter for large full scale drawings. Therefore it should be possible for firms that specialize in printing large drawings to plot the finished drawings. The program should consequently be able to export files in a commonly employed format which the plotting firm can read, for example the HP-GL/2 format or the AutoCAD formats dxf or dwg. Moreover, the program should be able to print a large drawing piece by piece on an ordinary A4 office printer, so one can use the assembled drawing in cases where professional appearance is not required. 

Test program available on Internet

It should be possible to pick up the drawing program on the Internet, at least for a trial period, so that interested instrument builders can borrow the program in order to read available drawings before deciding to purchase program or drawings.

 

The ideal model

In order to be ideal, a model for instrument drawings would have the following features:

  1. All drawings are gathered on one homepage.
  2. All drawings are in the same file format. 
  3. All drawings can be downloaded free of charge.

re 1) This is no doubt the most realistic of the three demands; one homepage could at least have links to all known and available instrument drawings.

re 2) Time will show which format will become the most widespread; but it is my hope that it will permit handling in programs which fulfill the demands stated above.

re 3) Measuring and drawing of music instruments is very time-consuming for an instrument builder and often incurs travelling expences. No one can expect that this work be done for nothing - even though many museums count on receiving free drawings of their own instruments, for further reproduction - so fulfilling this point is therefore dependent on finding support or sponsors

 

My model

For my drawing of the Pörschmann recorder at Musikhistorisk Museum in Copenhagen (the first in a planned series of drawings) I chose the full version of the program Malz++Kassner CAD 4.6, which satisfies all the above conditions. The program was developed by two German engineers, who kindly make their support available, and who also constantly are improving the program in accord with its users' wishes. Prices for the program range for the moment between DM 135 and DM 895 (about £ 46 - £ 310) depending on the version chosen.

A sample of my drawing can be downloaded from my homepage www.bergstrom.dk, where I also would be happy to include similar drawings or links to drawings by colleagues. The sample drawing is not complete, since I have to ask for a contribution towards expences from whomever wants a serviceable drawing sent by e-mail. The program can be downloaded from www.malz-kassner.com; the economy version suffices in order to read the drawing* and for the most common editing functions, whereas for those who would process drawings more intensively and have the possibility of plotting larger drawings I can recommend the professional version, expanded with a plug-in for export of HP-GL/2-files. 

(*addition April 1999: Malz++Kassner offers a free viewer for mkd-files which can be downloaded from the web site www.malz-kassner.com ). 

Most technical schools - no doubt also outside of Denmark - offer courses in technical drawing, primarily in the program AutoCAD. From my own experience I can heartily recommend following such a course as an introduction to the basic concepts involved; and I believe that, having worked with AutoCAD, most people will find the Malz-Kassner program considerably easier to use.

 

Other uses of technical drawing programs

Since procuring my drawing program, a few unexpected applications of it have cropped up. Most larger Renaissance wind instruments have a perforated fontanelle, with holes arranged in rosettes with one hole in the middle surrounded by circles of 6, 12 and 18 holes. Marking out these 37 holes six times round about the fontanelle is a rather tedious job, which I used to do with the help of a brass template. Now I could draw the figure with the 37 points distributed precisely geometrically on the computer and copy it 5 times in a row, so all 222 points of the fontanelle were marked on the drawing. This I printed on transparent foil, which was then taped around the fontanelle, and I could then drill the holes directly through foil and wood. As the foil is transparent, it is easy to tape it at the correct place. The distribution of holes was much more precise, and marking them much quicker than when it had to be done by hand.

The same method employing taped-on transparent foil proved advantageous when cutting out sheet brass for keys. 

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