Jump to content

Straight single-action truss rod?


Crusader
 Share

Recommended Posts

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?

Link to comment
Share on other sites

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.

  • Like 1
Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

20 hours ago, Bizman62 said:

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

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...