I have charted out a standard E9 set of strings to show this. If you groove the roller with a 60 degree tool to the depth of the string diameter, you end up with an exposed string height ( height above the plane of the roller tops) equal to half the diameter of the string. I have mathematically placed a stright-edge across the tops of the strings and mesaured the distance above or below the straight-edge. The results show that string 2 is very slightly above the straight-edge while strings 3 through 9 are below.

A=string
B=string gauge (diameter in thousands of an inch)
C=exposed string height
D=groove depth
E=distance of the exposed string top above or below the plane of the string tops (bar)

groove depth = string diameter

A    B    C     D      E 
F# .012 .0060 .0120  .0000
D# .015 .0075 .0150  .0001
G# .011 .0055 .0110 -.0034
E  .014 .0070 .0140 -.0033
B  .018 .0090 .0180 -.0028
G# .022 .0110 .0220 -.0022
F# .026 .0130 .0260 -.0017
E  .030 .0150 .0300 -.0011
D  .034 .0170 .0340 -.0006
B  .038 .0190 .0380  .0000

To a perfectionist like me, the above reults are a compromise. To me the purpose of gauged rollers goes beyond holding the strings in place. I want the gauged rollers to result in a string top plane which has no gaps for individual strings. The spreadsheet above goes beyond that requirement and results in a string-top plane that is parallel to the plane of the roller-top plane. It makes all of the strings stand above the rollers by the same amount. I experimented with a variation that gives similar readings to your straight-forward process but adjusts for the gaps,

To compensate for the gaps and to ensure that each string is resting in the groove, I adjusted each groove depth relative to the plane of the string tops. I increased the depth of each groove by .001" to make sure that the 3rd string rests completely in the groove.

groove depth graduated to give a flat plane across the top of the strings
A    B    C     D      E 
F# .012 .0050 .0130  .0000
D# .015 .0064 .0161  .0000
G# .011 .0079 .0086  .0000
E  .014 .0093 .0117  .0000
B  .018 .0108 .0162  .0000
G# .022 .0122 .0208  .0000
F# .026 .0137 .0253  .0000
E  .030 .0151 .0299  .0000
D  .034 .0166 .0344  .0000
B  .038 .0180 .0390  .0000

Karlis

[This message was edited by Karlis Abolins on 20 January 2005 at 10:23 AM.]

I'll post some pics when it's done, which could take some time.

Just a thought...maybe it works.

------------------
Peter den Hartogh
1970 Emmons D10 P/P; 1977 Sho-Bud D10 ProIII Custom;
1975 Fender Artist S10; Remington U12; 1947 Gibson BR4;
Internationally Accredited 3D Animation Academy

Per, You might want to consider using a wedge arrangement rather than a screw and pivot arrangement to get better contact between the parts.

And by the way, your 3-D renderings are absolutely fantastic!

Also, I suspect the rollers would move around a bit from the strings' back and forth movements . Even the tiniest difference in resistance between the two directions would eventually result in the roller rotating away from the perfect position. I'm just guessing here, though.

But most importantly, in my not-so-humble opinion, the combined efforts of Peter and myself look way cooler ...

--------------------
Emmons Legrande II D10 8+5, Sho-Bud Pro III Custom SD10 4+5, Goodrich 120, Peavey Nashville 1000

[This message was edited by Per Berner on 22 January 2005 at 06:34 AM.]

quote:

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About 20 years ago there was a guy who made an adjustable roller arrangement/nut whereby each roller was suspended in its own cylinder and was adjusted from the underside of the guitar with a screw.

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Also, just about anything is possible if you have enough determination. If my brain can come up with a technical solution, I think it will also come up with a way to master the milling machine. After all, it has managed to come up with a way of getting half-decent sounds out a pedal steel guitar!

1. It seems to me that the more metal to metal contact under the roller, the more string vibration will reach the body of the guitar equaling truer tone and greater sustain.

2. If the roller rocks while it's Height is adjusted then scale length is changed. (I agree that this would be minimal)

3. Possible solution: I Wish I knew how to attach a drawing of this. For the idea consider the shims at your local lumber yard, the ones you use when setting a door to fill the gap over and at the sides of the door jam. Individually they form very sharp triangles. Take two of them and place one on top of the other on a flat surface with the points of the triangles in opposite directions. Hold the top one stationary and slide the lower one toward it's point. You will notice that the height of the top one will increase as the second is slid underneath it and the top of the first one is and remains a flat surface.

Now picture it smaller and made of metal with the roller on the top of the upper triangle and an adjustment screw to slide the lower triangle under the first. Basically a sliding inclined plane under a stationary inclined plane. This would allow for continuous metal to metal contact under the roller. The roller would not rock since the top piece is flat and would raise straight up. It should be very stable and not cause problems with the guitar staying in tune.

Steve: You certainly have a point about the metal to metal contact issue. IMO, most important is to avoid loose-fitting rollers - that can kill sustain totally. The change in scale length that would occur when raising or lowering a pivoting roller would make absolutely no difference - I doubt it could even be measured.

Isn't the drawing in Karlis's last post just about what you are describing?

Lots of way to "skin the cat", ..never knew why anyone would want to do that though. Simplicity pleads for itself re configuration et al.

Re the solid pivot shown above, ..consider it facing down at the end instead of horizontal.

The Strat string saddles (miniature edition) would do everything but roll, ..Strat sustain/tone seems to please most country pickers.

So it all comes around to when do we need rollers, and how big should they be, and how should they be attached to the body/neck/ or other favorite structure. Should they be adjustable so you can have string top planarity, or bottom planarity for the capo folk (compensating for string stiffness
,"overshoot", and gauge tolerance.

Keyed tuners and long string length beyond the nut to me indicate rollers, ..keyless with short string length beyond the nut indicates no rollers = like Strat saddles for planarity adjust.

Great graphics above, ..nothing like a picture or photo to say a lot quickly.

Re the "body contact/sustain/tone" issue; I believe that the vibrations of one string exciting the other strings is the point of consideration. If it does it thru the body, the bodies Q at resonance(s)will act as a filter. To the degree that the strings vibration excites the other strings thru the bridge/nut, the effect upon tone/sustain will be increased (positive?). Simplicity pleads for itself again, ..a rod, and on the end usually occupied by the changer for the greater effect.

Now that will give a greater design problem for the string top planarity folk, ..how to make a changer (adjustable) so that the string top planarity is achieved.

[This message was edited by ed packard on 23 January 2005 at 08:39 AM.]

What happens if the strings at the nut run UNDERNEATH a 1/4 inch bar. That would make the tops of the strings absolutely co-planar.

quote:

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Re the solid pivot shown above, ..consider it facing down at the end instead of horizontal.

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If the unit is rotated 90 deg CW, it can rock left/right, but not up/down. So how would the height be adjustable?

It also means that existing keyheads can be "shaved" off to make place for the groove and the saddles.

It can also accomodate adjustment screws from the bottom, as has been suggested previously.

[This message was edited by Peter on 23 January 2005 at 03:28 PM.]