Arash Posted July 15, 2014 Share Posted July 15, 2014 it's first time I'm using an Excel Spreadsheet to calculate a Tractrix horn. I took the numbers into Autocad and the CAD drew the curves but I can't find any relevance between these curves with a real horn! the horn I calculated is fc=260hz and 58cm width and 23 height and 35cm length. can anybody shed some light here? Quote Link to comment Share on other sites More sharing options...
Schu Posted July 15, 2014 Share Posted July 15, 2014 (edited) Ive often wondered, since I've used autocad and illustraor for years to engineer consumer goods, what the parameters are for a "proper" dispersion pattern... because I could come up with a hundred different layouts. Perhaps someone with actual proof to a good can answer up. Edited July 15, 2014 by Schu 1 Quote Link to comment Share on other sites More sharing options...
Marvel Posted July 15, 2014 Share Posted July 15, 2014 (edited) A tractrix curve, for the most part is rather straightforward. Are you using the spreadsheet written by Erik Forker in Germany? There is a bunch of info available for the quirks in the layout. I know he has it set up so you can copy a row or column of data to put into Autocad to make the templates correct. http://www.volvotreter.de/index.htm Look in the downloads section Bruce Edited July 15, 2014 by Marvel 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted July 15, 2014 Share Posted July 15, 2014 (edited) What constitutes corrrect? The slight pinching of the throat before flaring at the horn? And if so how much pinching and at what rate or ratio should the horn flare? Edited July 15, 2014 by Schu 1 Quote Link to comment Share on other sites More sharing options...
Fjd Posted July 15, 2014 Share Posted July 15, 2014 (edited) I would take a look at Bruce's link and download the excel file and experiment with the parameters. I'm not a horn expert and maybe some will enhance (or correct if necessary) my comment; however, the way I understand it is that the tractrix curve is a formula assuming that a 'tangent line' to any point on the horn's inside curve will reach the central axis of the horn with a non-changing in length line. At the termination point of the mouth the tangent line will be perpendicular (90 degrees) to the axis and will become the radius of the horn mouth. The attached shows the 90 degree termination angle of the tractrix mouth compared to exponential horn mouth. Take a look at this animated gif on wiki. I'm not sure why I can't link the animation here and only the link shows. http://upload.wikimedia.org/wikipedia/en/2/27/Tractrixtry.gif Edited July 15, 2014 by Fjd 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted July 15, 2014 Share Posted July 15, 2014 I'm not a horn expert and maybe some will enhance (or correct if necessary) my comment; however, the way I understand it is that the tractrix curve is a formula assuming that a 'tangent' to any point on the horn's inside curve will reach the central axis of the horn with a non-changing in length line. very interesting... Quote Link to comment Share on other sites More sharing options...
Arash Posted July 15, 2014 Author Share Posted July 15, 2014 I'm using the excel file you mentioned Tractrix V1.4. I think I'm back on the road again. the problem was about W/H ratio. I mistook Width as Height. now this is center template: Quote Link to comment Share on other sites More sharing options...
Marvel Posted July 15, 2014 Share Posted July 15, 2014 The slight pinching of the throat before flaring at the horn? And if so how much pinching and at what rate or ratio should the horn flare? Erik's spreadsheet is set up to have the top and bottom pieces of the horn to be flat. To have the flare be correct, the curved sides actually have to 'pinch' back in a bit before they curve outward.Alk K. had the same thing on his early horns. Bruce 1 Quote Link to comment Share on other sites More sharing options...
Arash Posted July 15, 2014 Author Share Posted July 15, 2014 (edited) there is no need to copy the data from excel to a .txt file and then change the extension to .src. just copy them directly into command like of Autocad and press Enter and it would do the job. Edited July 15, 2014 by Arash Quote Link to comment Share on other sites More sharing options...
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