Do we need a roller-style nut?

[Gary Patterson]

Everyone uses a roller nut to minimize friction and presumably minimize string hysteresis when the pulls are executed. However, ultimately, the string terminates at a fixed point, that being the tuner shaft. Along the way, we include that part of the string behind the nut in the pull, which presumably increases, incrementally, the necessary movement of the changer finger to achieve the desired tuning change.

Has anyone tried the "Floyd Rose" (I hate those things on guitars) concept of locking the strings at the nut? It seems this would reduce the pull distance, eliminate any friction problems, and make leveling the plane of the strings simpler (no gauged rollers, just carefully adjusted nut slot depth). Probably would stabilze tuning, too, although that doesn't seem like much of a problem anyway.

Does anyone know of a downside to this notion?

[Georg]

With that concept; nothing comes up above the strings that I can hit with the bar when sliding over the "nut" ?

Also, will the locking be close enough to the "nut" to avoid the string sliding on long pulls and hang on return to neutral - hysteresis ?
- I have experienced enough (too much) hysteresis on a keyless with solid nut-bar, despite shortening the overshoot to a minimum, and string-grooves will probably tend to cause more hang than a well-polished bar.

[ed packard]

Gary..Georg,

On the BEAST I use an interchangeable rod as a non rotating "nut", but on the players right. The amount of back and forth motion across it, or maybe the ultrasonic machining effect caused by the vibrating string caused a bit of grooving on a brass rod...not as much as is caused to the aluminum finger(s) of a standard changer. A Zirconia rod is impervious to the grooving effect.

The ratio of the wound string bumps (wound strings) to the nut diameter might be considered as sticking points in string motion across the nut.

[richard37066]

Gary -

I have a GFI D10 "keyless". The "nut" is a chrome plated rod approximately 1/4" in diameter. The distance from the center of the nut to the termination points of the tuning "fingers" averages 1/2".

The scale length is 24". If one assumes that the entire string stretches, for example, on a raise then the string must slide across that rod. A whole-tone raise moves the contact point on the changer finger by a little more than 1mm. The movement across the "nut" is then approximately 1/49th of 1mm or 0.0008 inch - less than a thousandth. I have experienced absolutely no sign of hysteresis on the instrument.

From a purely mechanical point of view, I rebel at the idea of the string sliding across the nut. However, since it has posed no problem I view it as an acceptable design. Much simpler than an array of captive rollers. Keep in mind that, on a conventional keyhead, the length of the string beyond the "nut" approaches some 8" on strings 5&6 on some instruments - some 16 times that of my GFI. I'd be very leery of using a solid "nut" under those circumstances. Remember, too, that detuning of the order of 5 to 10 cents is quite audible thus a very small "hangup" might very well be problematic.

Lastly - it appears that GFI uses a proprietary roller nut on instruments with conventional keyheads. Does that tell us something? Gene Fields ain't no fool.

Richard

[Gary Patterson]

I don't think I properly described my proposition. With the strings clamped down, the clamping point would replace the nut, and there would be no sliding (altho some Floyd Rose designs use a clamp behind the nut, for reasons I don't fathom).

Georg, I rarely slide my bar over the nut to play open strings, so I hadn't thought of that restriction.

Here's a pic of what I had in mind, installed on a 6-string: Of course, you'd have to undo the clamps to tune, but this concept might reduce the need.

It also occurs to me that such a design would omit the need for angled, stepped keyheads. The tuners could be mounted to parallel bar stock, with the strings angled to the nut like a typical non-steel guitar. This would be a boon to the low-volume or one-time builder who can't cast and/or machine a stepped keyhead.

[Georg]

Hmmm. Modified to get the screwhead flush with the clamping piece and rounding those pieces a little, it may work for me on regular PSGs.

Such clamping may work even better as bridge on my own design with changer as part of full keyhead on the left. Preventing sliding/hysteresis at the bridge is as important (to me at least) as at the nut, and the clamp's height doesn't get in the way there. Obviously I can't clamp down the strings at the nut on my design, but I have already designed friction-free nut rollers.