What on earth do I do with this? (Truss rod question)

[Tavy]

I can't believe anyone (builder included) has ever been able to adjust this?

Suggestions?

[pops1]

Do you adjust by turning the nut? or is their a hex head in the end of the rod? With a ball end hex you may get in there, if it has a hex in the end.

[Tavy]

Do you adjust by turning the nut? or is their a hex head in the end of the rod? With a ball end hex you may get in there, if it has a hex in the end.

No hex in the end, no thread on the end either, though there is on the fretboard side of the that nut (which is so tight to the sides, I can't believe it would turn even if I could get to it).

[Tobin]

Any chance that the truss rod is designed to be adjusted from the other end? Like inside the body, through the end pin hole?

[NEH57]

Is that the 'fixed' point of the assy and is the adjustable end of the rod inside the Mando via the soundhole ? needing a long Allen key to adjust ? (snap....)

[pops1]

And we'll have fun fun fun ---------

[Tavy]

Nothing down the other end.

[CES]

What you appear to have there is a "nonadjustable neck stabilizer" . Good luck!

[Frank Ford]

Look more closely at the end of the cylindrical section - are you SURE there's no internal hex?

Can't tell from here what you have, but it looks like somebody put a hex nut over the threaded rod as a spacer or some such, followed by a washer, and finally the internal hex nut - or it could be some aberrant kind of setup. . .

[Frank Ford]

OOPS, duplicate post

[NEH57]

Given that, the end has that unusual marking on and 'appears to be' wider than the threaded section, I would wonder if it is in fact a 'cap' rather than part of the rod protecting the socket end. Someone with some knowledge of engineering might recognise those marks, possibly from a 'chuck'. It doesn't look to be a standard rod because the hex head isn't visible, but who is going to make a length of bar that long into a threaded rod when threaded rod is already a 'thing' ?

[bernabe]

It appears to be installed just beneath the fingerboard. Maybe it just looks that way, however if so, may not be functional. Is that the rod threads showing through that hole where the nut goes?

[MikeEdgerton]

They actually make this special tool for situations like this. I assume they are available on your side of the pond as well.

[Folkmusician.com]

They actually make this special tool for situations like this. I assume they are available on your side of the pond as well.

Favorite post in quite a while !

[Dale Ludewig]

Hah! I think I'd go with Mike E. on this one.
Actually, it's quite the mystery. Functional or not, I'd like to know the history/logic on this. Aliens?

[Ivan Kelsall]

Looking at the cylindrical 'whatever',it seems to me that the only way you could tighten/loosen it is if it does indeed have a hex.socket in it. - how else can you turn a cylinder ?. But - Tavy's been repairing instruments for a long time,& he can't find any hex. - so ?.

I'm inclined to think that it isn't a truss rod in the sense that we know them & it'as as Chuck suggests,a non adjustable stabilizer. Unless there's quite a gap at the sides of the nut (covered), which i don't think is the case,you can't even get a spanner on that either. It may very well have been fitted & then tension applied via a covered nut / socket which is now under the fingerboard much as Tobin suggests,
It's weird - X-Ray anyone ??,

Ivan

[Shelagh Moore]

Funnily enough I have one on the bench almost exactly the same Tavy... no apparent easy way to turn it.

[NEH57]

Dimensions of components still make it look like a cap to protect the thread or just tidy up the finish to me. That 'helter skelter' striation and the angle of the stripes suggest perhaps it was 'spun on' by pulling off some 'tape' or some such which had been pre-applied and has led to that 'bright/dull' appearance.
In the absence of all else, ie. if a pair of long nose pliers won't tweak it into turning, I would drop a drill into it, just enough to create a viable 'notch' then use a very fine 'drift' to try tapping it anti clockwise to see if it comes loose.
It may well not be ferrous, so a magnet might give you a clue. If it's stainless it's 99.9% a cap.

If removed, with the washer, a thin walled tube socket of typical type could presumably be applied to the fastener.

Like this.....

I have '0' experience working on Mandolins but quite a lot problem solving and discovering ???'s on old Honda bikes

[Tavy]

I think I may have a solution, will report back soon...

[Tavy]

Managed to turn it round and:



Doh!

Not sure how much it does yet though...

The instrument BTW is an F4 copy by Deep Ocean / Otto Dvorak.

[Tobin]

So did you cut/grind/file those notches there, or were they there already? Can't tell in the original pic.

It really does look like the inside of that thing is set up for using a hex key, but it could just be an optical illusion at that angle.

[Dale Ludewig]

At this point, it looks like it's supposed to be a lock nut, just to keep the main nut from coming loose due to incredible vibrations that a truss rod has to sustain.

[Tavy]

Tobin: No I didn't cut them, just couldn't see them because of their orientation. And no, definitely no hex socket in there, it's all round.

Dale: Like I said, I'm not sure if tightening it up actually does anything as all it seems to do is push against the other nut!

[NEH57]

It is a lock nut.....of sorts. You screw it off then use a thin wall socket on a bar to either tighten or loosen the fastener/nut then replace the slotted barrel. Or at least that is the principal. It is possible to get a flex drive screwdriver or a carburettor screwdriver on a 90 degree pinion drive which would whizz that fastener off in a jiffy. Carb drivers are expensive the flex drive ones generally pretty naff but they'd do the job........for the odd one probably as easy to get it off with a drift. It is not designed to tighten the bar through the fastener. It will just torque it up and chew the thread

[Ivan Kelsall]

From Tavy's new photo,it seems that the hex.nut is simply something for the slotted cylinder (let's call it a 'nut') / washer to push against when tightening it up. There's nothing else on the 'truss rod' to push against.

So - we have a threaded truss rod,with a hex.nut screwed onto it,a washer placed behind the nut & the slotted nut behind that to apply the pressure. As long as the hex.nut can't turn,if the slotted nut is tightened,the truss road will be compressed. As NEH57 says,you could deform the screw thread if the slotted nut were cranked up too hard. But i can't help feeling that if that was the case,a deformed screw thread would be the least of your worries !.

It's not the finest TR config. that i've ever seen,but maybe it worked ok,
Ivan