Truss rod on a JEM

[Metallion]

Are all the JEM guitars fitted with One-way truss-rods?

As you tighten the Truss-rod nut on a JEM - with its steel bar above flexing upwards when the rod below are shortened - the rod pushes upwards on the center of the fretboard.

Wouldn't this result in a high risk of the Fretboard being split from the neck from the pressure?




Is the truss rod channel straight?

[bancika]

No, in order to make truss rod work you have to make it with some initial curve. If it's dead straight you never know which direction will the bow go take once you start tightening it. And it shouldn't be bent like the one on your picture because it will make too much pressure concentrated at one point (hump) which will probably make humpy neck. It should be done the other way round, so it distributes pressure over whole length of the neck.


Edit: I'm not 100% sure that it's the way it's done on JEM, but it should be....

Cheers

[Metallion]

The Ill. is exaggerated, showing the FORCES.

Originally Posted by bancika

If it's dead straight you never know which direction will the bow go take once you start tightening it.

The Rod ONLY bends UPPWARDS when the nut is tightened. I know. I have one here to try.

And it shouldn't be bent like the one on your picture because it will make too much pressure concentrated at one point (hump) which will probably make humpy neck.

See above.

It should be done the other way round, so it distributes pressure over whole length of the neck..

You're talking about the CHANNEL, right?
This Rod bends UPPWARDS. That is the physics of that construction and can not work any other way, unless you have a 2-way truss-rod with the adjustment-nut fixed to the bottom Rod, which isn't the case with JEM guitars.

And it IS positioned as described, according to the pictures:


http://www.jemsite.com/jem/necks.htm

If I turned the rod up-side-down, it would EXAGGERATE the bend on the neck that the strings impact.

Some more Data:
http://projectguitar.com/tut/truss.htm
http://www.ibanez87.it/italiano/altr...-fabio-18.aspx

[nuno]

Originally Posted by Metallion

Are all the JEM guitars fitted with One-way truss-rods?

yep, one way only

[Metallion]

Proof: Effect of tightening this rod:

[bancika]

Ok, my reply applies to simple strat-style rods. For strat style rods you only have a single rod so tightening it actually means trying to make it flat (initial state is bowed) by anchoring to the neck wood (red arrows). You're tightening the nut which makes rod shorter. But it's totally different philosophy. This one has large flat surface so it distributes pressure evenly throughout the neck.

[brothersnowgone]

Originally Posted by Metallion

Wouldn't this result in a high risk of the Fretboard being split from the neck from the pressure?

If this were really true do you think they would still be doing it on thier guitars? Believe me the risk is very low, with the amount of glue holding a fretboard on I wouldn't worry about it too much.