View Full Version : Truss rod question

May-04-2016, 1:21pm
Curious if Gibson used double acting truss rods on their early necks. Trying to adjust the truss rod on an original plectrum neck, but as I tighten it, the neck seems to go lower in the center. Any suggestions?

Roger Siminoff
May-04-2016, 4:43pm
DoctorB... Gibson's truss rod system was designed by Thaddeus "Ted" McHugh and was awarded a US Patent in Feb of 1923. It was McHugh's idea to embed the truss rod in an arc in which the peghead-end of the truss rod was low in the peghead, the middle of the rod was close to the fretboard, and the heel-end of the truss rod was low in the neck heel. (It was a single rod, not a double rod.) However, the design was flawed. In McHugh's design, when the rod was tightened, it would work to a point, but when tightened further, the rod wanted to straighten which caused a "hollow" or low spot in the neck (which is what you are experiencing). If you loosen the truss rod a bit, your neck should straighten back out. In the early 1930,s Gibson inverted the truss rod so that the center of the rod sat low in the center of the neck and the two anchor points were high in the neck - and that's that way it has stayed up to today.