Crusader Posted November 21, 2020 Report Share Posted November 21, 2020 I've been doing some necks and I'm up to the filler pieces in the Gibson style. I've done them before but I just wondered if the filler has to be curved or if it can be straight (because its so thin) and just push it up to the truss rod when gluing. So I googled it and came up with more than I bargained for. On MLP people were saying Gibson truss rods were straight up until 1960 and this had me totally bewildered Some people were saying Gibson did straight single-action truss rods and others said they won't work and need to have a curve. I didn't read-on to see if they resolved it because the posts were from 2011. But it occurred to me from personal experience that really thick necks (ie. 1950's) don't really need a truss rod. Its only when necks started to become thinner in the 1960's they need it. The age of the timber may also be a factor (drier, stiffer) Does anyone here know about this? Does this mean my '59 Reissue would have a straight truss rod? Quote Link to comment Share on other sites More sharing options...
curtisa Posted November 21, 2020 Report Share Posted November 21, 2020 I pulled a single acting truss rod from an old Strat copy neck as a practice run for steaming off a fretboard a while back. It looks almost exactly the same as a double acting rod with the flat steel bar on top of the straight threaded rod, the difference being that the adjuster nut can only be done up to bend the rod backwards. Undoing the nut beyond the slack point just results in the nut falling off the end. Long story short, straight single acting rods exist, but the mechanism for making them bend the 'right' way is different to the traditional rod sitting in a curved channel. Whether the period-correctness is important to you, that's entirely up to you. 1 Quote Link to comment Share on other sites More sharing options...
Crusader Posted November 21, 2020 Author Report Share Posted November 21, 2020 5 hours ago, curtisa said: .....It looks almost exactly the same as a double acting rod with the flat steel bar on top of the straight threaded rod, the difference being that the adjuster nut can only be done up to bend the rod backwards. Undoing the nut beyond the slack point just results in the nut falling off the end... Interesting but now I'm even more bewildered, why would you want the rod to bend the other way? I thought those truss rods with a steel bar attached IS a double action rod. The 335 copy I got for my 12th birthday had a U channel with the rod inside it and I've seen variations of the same concept. It was about 30 years ago I saw an old Fender neck in a shop that had been cut right down the centre revealing the truss rod and its curve. I didn't know any terminology for them I just knew Fenders & Gibsons had one type and copies had the other Reading the discussion I mentioned I don't think the Gibsons had an extra bar attached to the rod or anything its just straight and set deeper into the neck. I have Googled this but haven't yet found any images. I'm finding it very interesting because I used to wonder why my 335 needed the U-bar Quote Link to comment Share on other sites More sharing options...
Crusader Posted November 21, 2020 Author Report Share Posted November 21, 2020 Errr don't answer that... I understand why my 335 needed the U-bar. I perceive the concept behind that type of truss rod. I haven't been able to find any info or images of the old Gibson straight rod yet. But its exactly what I thought you could do instead of having the U-bar. Have the rod deeper into the neck Now I'm still trying to find any pictures Quote Link to comment Share on other sites More sharing options...
Bizman62 Posted November 21, 2020 Report Share Posted November 21, 2020 http://www.frets.com/FretsPages/Musician/GenSetup/TrussRods/TrussRodAdj/tradj.html http://www.redspecial-library.com/tutorials/neck-tutorial-1 Do these shed any light? Quote Link to comment Share on other sites More sharing options...
curtisa Posted November 21, 2020 Report Share Posted November 21, 2020 https://www.mylespaul.com/threads/does-a-straight-truss-rod-channel-really-work.406227/ The discussion here (post #3) perhaps explains better how the straight channel single acting rod worked for Gibson. The key appears to be that the body-end of the rod is set further below the fretboard than the nut-end. When the strings are tensioned up the neck will want to pull forward into a slight curve as you'd expect. Because the rod is placed at a slight negative angle relative to the curve of the neck, tightening the nut wants to pull the nut-end back away from the curve. Hence you have your adjustability to compensate for excess forward bow due to string tension. The double acting rod (and the whacky single acting one I found in my Strat neck) with the flat bar welded on top just simplify the installation process as they no longer rely on a channel that needs to be cut at a falling angle (Gibson) or some complicated curve (Fender) to work. Quote Link to comment Share on other sites More sharing options...
Crusader Posted November 22, 2020 Author Report Share Posted November 22, 2020 20 hours ago, Bizman62 said: http://www.frets.com/FretsPages/Musician/GenSetup/TrussRods/TrussRodAdj/tradj.html Do these shed any light? Yes I see the light! that is a picture of a straight rod, I think I've seen it before but I didn't take much notice, I wish it was a clearer picture. It seems to be parallel with the fretboard which is interesting 17 hours ago, curtisa said: https://www.mylespaul.com/threads/does-a-straight-truss-rod-channel-really-work.406227/ The discussion here (post #3) perhaps explains better how the straight channel single acting rod worked for Gibson. The key appears to be that the body-end of the rod is set further below the fretboard than the nut-end. When the strings are tensioned up the neck will want to pull forward into a slight curve as you'd expect. Because the rod is placed at a slight negative angle relative to the curve of the neck, tightening the nut wants to pull the nut-end back away from the curve. Hence you have your adjustability to compensate for excess forward bow due to string tension. The double acting rod (and the whacky single acting one I found in my Strat neck) with the flat bar welded on top just simplify the installation process as they no longer rely on a channel that needs to be cut at a falling angle (Gibson) or some complicated curve (Fender) to work. Yes it seems to me the rod forms a triangle with the line of the fretboard and I can understand that it would work in a neck with some girth, but in a thin neck there just isn't enough wood there to form enough of a triangle - at least thats how it seems to me I know from my own experience that a straight rod doesn't work when its not far under the fretboard - My first four necks with a single rod worked fine but on my fifth for whatever reason the curve was not enough and it just didn't do anything. It was a Fender style with a skunk stripe so I routed that out and glued in a strip of wood and re-routed the curve. It worked okay after that....what a job though! The curve isn't all that complicated. All I did was make a test neck and stuck about four 52g strings on it and tightened them up. Then I traced the curve onto a plan and that was it. I used that curve for the truss rod. Making the jig was the hard part, the thing of nightmares Quote Link to comment Share on other sites More sharing options...
Bizman62 Posted November 22, 2020 Report Share Posted November 22, 2020 Yet another: http://www.frets.com/FretsPages/General/Glossary/TrussRod/trussrod.html Quote Link to comment Share on other sites More sharing options...
Crusader Posted November 22, 2020 Author Report Share Posted November 22, 2020 Ah yes that’s the one I’ve seen, it’s a Taylor so I didn’t study it much Quote Link to comment Share on other sites More sharing options...
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