{"id":38,"date":"2008-01-01T00:00:00","date_gmt":"2007-12-31T23:00:00","guid":{"rendered":"http:\/\/www.thestrandbergs.com\/blog\/2008\/01\/01\/in-god-we-truss\/"},"modified":"2008-01-13T15:18:04","modified_gmt":"2008-01-13T14:18:04","slug":"in-god-we-truss","status":"publish","type":"post","link":"http:\/\/guitarworks.thestrandbergs.com\/2008\/01\/01\/in-god-we-truss\/","title":{"rendered":"In God We Truss?"},"content":{"rendered":"

I have been thinking a lot about what the twisted neck design will do to the stability of the neck and the truss rod. I did some sketches to see how the center of the rotation would affect the neck.<\/p>\n

\"Axis<\/a><\/p>\n

The picture above shows a twisted fingerboard seen from the short end. The leaning lines on the sides illustrate the width of a would be nut once the fingerboard had been cut to size. The way it looked at first (to the left), the axis would make a big impact. The top left image has the center of rotation where the strings would be, the mid left has the center in the center of the fingerboard and the bottom left has the center in the center of the would be neck. But if you would imagine that you lay the neck flat on a table and rotated it and then looked again from the short end, you would see the images on the right hand side. In the illustration, I have simply moved the twisted piece on the X-axis until the centers of the fingerboards align. It seems that the center of the rotation of the twist can be compensated for.<\/p>\n

I have been pondering using a twisted aluminum T-beam to make up the neck, which was the reason for making the above sketches. As Alexander Gorm Ost explains in his blog it is easier said than done. But then it dawned on me that his approach of bolting the horizontal beam to the vertical would allow building a “flex compensator” into the neck instead of a tradtional truss rod.<\/p>\n

\"Flex<\/a><\/p>\n

My plan was (if the center of rotation would have messed up the “axial straightness” of the truss-rod) that this would allow compensation of the flex of the neck in both directions. But since the center of rotation does not make a difference, one could use either the above design or bolt TWO beams onto the top one and route a rod between them as a traditional truss rod. Alternatively, bolt two beams onto the top using the above design – this would allow adjustment of the torsion of the neck as well! One would have to consider weight though.<\/p>\n

I went out and bought myself a copy of the old book of formulas for mechanics that I had in school 25 years ago (glad it was still in print) and did some very rough calculations on the deformation of a neck.<\/p>\n

Assuming a string pull of 40 kgs ~ 400 N and a distance between string and fingerboard of 2 mm, then the a torque of 800 Nmm that is trying to pull the neck upwards. The deformation f is (M \/ 2EI)L^2. Assuming the most basic case of a neck that is rectangular in shape, the value I is bh^3\/12 where b is the width and h is the height. So, let’s assume we have a rectangular neck that is 5 mm wide and 15 mm high. This gives us I = 1406. For aluminum, E is 70000 N\/mm^2. L, the length of the beam (i.e. neck), is 490mm. f = 800 * 490^2 \/ (2 * 70000 * 1406) = 0,97 mm. So, an aluminum beam 5 wide and 15 mm high would be bent about a millimeter by a set of .009 – .042 strings. It looks like it should be possible to create a neck without truss rod with reasonable comfort. I will do some more calculations though, before deciding… For instance, a 10×10 rod would be deformed 1,64 mm, which is way too much.<\/p>\n","protected":false},"excerpt":{"rendered":"

I have been thinking a lot about what the twisted neck design will do to the stability of the neck and the truss rod. I did some sketches to see how the center of the rotation would affect the neck. The picture above shows a twisted fingerboard seen from the short end. The leaning lines […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[],"_links":{"self":[{"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/posts\/38"}],"collection":[{"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/comments?post=38"}],"version-history":[{"count":0,"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/posts\/38\/revisions"}],"wp:attachment":[{"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/media?parent=38"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/categories?post=38"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/guitarworks.thestrandbergs.com\/wp-json\/wp\/v2\/tags?post=38"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}