Truss rod

The Truss Rod (English truss rod ) is an adjustable steel rod, which is installed on the inside in the neck of some musical instruments from the family of lutes. The rod acts, put under tension, the tension of the strings against, thus balancing the thus caused curvature of the instrument from the neck. Since gut and nylon strings exert only a slight pull on the neck, neck tension rods are mainly used fretted instrument with steel strings. Especially Western guitars, archtop guitars, solid body electric guitars and basses have usually a neck tie rod.

History

Already at the beginning of the 18th century luthiers have sought in various ways according to a reinforcement of the neck to counteract the partially enormous string tension on the neck. The first truss rods consisted only of a strip of ebony, which fully satisfied the conditions of that time, because the gut strings used had no particularly high string tension. At the beginning of the 19th century American guitar manufacturers began to produce steel string guitars, the string tension was much higher than that of gut strings, making the ebony strip used until then to strengthen the neck is not nearly enough more. Thus began the designers to enlarge the throat cross-section, of which, in turn, suffered the playability, as these necks were hard to embrace.

In the early 1920s invented Lloyd Loar, at that time head of the development department of the U.S. musical instrument manufacturer Gibson Guitar Corporation, the adjustable truss rod which made ​​it possible to make the necks back slimmer. By the early 1950s were due to the patent law of Gibson guitars have built such a rod. After the expiration of the patent all guitar manufacturers switched to the adjustable truss rod - up to Martin Guitars, who used an adjustable steel bar until 1985.

Construction

The Truss Rod is a longitudinal channel in the interior of the neck. The Mill and the insertion of the rod is done either from the fingerboard side from before the fingerboard is glued to the neck, or back of the neck from. In the latter case, if the neck is not painted opaque, the filling of the milled channel are perceived from the outside. In some cases a different colored wood is used for this purpose (so-called Skunk Stripe). The channel for the neck truss rod describes viewed from the fretboard ago, a slightly convex arc. In the middle of the neck of the rod is located, therefore, the fingerboard is closest. At the ends it is screwed to the timber neck such that it can be set under tensile stress. The setting of this voltage is made ​​depending on guitar model either at the head or at the instrument connected to the body end of the neck. Especially in the latter design, the adjustment of the truss rod can be done with some instrument types with threaded neck only after unscrewing the neck. There are several solutions to this problem - usually with the aim of hiding the Truss Rod outward as possible, but the setting still the same to make comfortable.

Operation

Substituting the neck tension rod under tension thus causing the curvature of the rod, that the fingerboard in the middle is pushed upwards and the neck as seen from the player, turns backwards. However, this tendency counteracts the train of the strings. With an optimally adjusted neck, this is even slightly bend forward because the string vibration in the middle of the string length while playing the instrument has the largest amplitude. If the voltage of the rod is too large, the neck is perfectly straight or bends backwards. The strings then touch when you hit the fast fretboard (with fretless neck) or the frets and rattle. If the voltage of the clamping bar set too low, the neck bends forward too much. Then there arises a problem that the playability of the instrument by the high string action is impaired (distance of the strings to the fretboard ). Precise game and good intonation are so severe possible. To adjust the neck tension rod with an Allen wrench or screwdriver is recommended that the strings to relax before.

As a rule, new instruments should be delivered from the factory with a good attitude of the Truss rod. An adjustment of the rod may be attached, for example, if strings of a different gauge are reared.