Loar Fret spacings.

[Beanzy]

From the supplied photograph the same ratio of error appears to occur in the second octave even though those distances are not the same so it is unlikely to be a mechanical error low down or the repeat would completely mis-align due to the larger measurements in the lower octave.

Accurate charts for 12TET were only published by William Braid-White in 1917, indeed the first accurate sub-divisions into 'cents' had only been done by Ellis in 1864 using tuning forks. What he found was that people claiming to be tuning in ET were not in fact doing so (1885) If the board patterns repeat the ratio of error further up but not the scale, then we are most likely dealing with a different temperament approach, possibly taken from earlier patterns & decisions, rather than some simple mechanical loosening or flexibility during the Loar period as postulated by some.

[MikeEdgerton]

Mike - I understand your point,but to have the spacers 'wear',they'd have to be loose.

Actually not at all. The bad fret spacing has been discussed before. One conclusion way back was that the gang saw was off because the spacers were off. The spacers wouldn't have to be loose.

Comparing how a modern saw is built to how a piece of equipment that was built in a manufacturing company in 1900 or so is pretty presumptuous. Beyond basics I'm pretty sure they made it up as they went along. Martin actually discovered in the 80's that their jigs had worn so bad that their headstock shape had changed. Things change without people noticing it.

If anybody cares to see past discussions on the Loar era fret spacing problems just dig through this search string. You'll have the pluck the applicable ones out.

[Ivan Kelsall]

Hi Mike - I was addressing the ''wear'' factor. That could only occur if the spacers were loose enough to turn. Of course,if the spacers were dimensionally wrong to begin with,then there would be errors regardless. It does occur to me that Gibson should have had a checking fixture (a Master Template) against which they could check the cut fingerboards for any errors. Simply relying on everything being ok all the time,isn't a sound production procedure.

As far as being 'presumptuous',most engineering machining methodologies had been well worked out by 1900 as i'm sure Henry Ford would have been well aware. Primitive milling machines were around in 1830 & the first 'proper' milling machines were being used in 1916. My argument was that simply clamping the cutters between the spacers wouldn't be good enough to ensure that the cutters wouldn't simply hit the workpiece (fingerboard) & jam. A more positive form of cutter fitment to the arbor was needed - the key ridge on the arbor & the matching slot in the cutter hole. In fact since their invention,horizontal milling machines have depended on this system in order to even work. So 'presumption' had nothing to do with it other than maybe i was presumptious enough to expect Gibson to use the 'obvious & correct 'machining method - so,point taken !. If they didn't................... ???,
Ivan

[Jerry Byers]

This has been an interesting thread. I'm not an audio engineer, so some of that discussion is beyond me. But the process engineer in me is curious about the spacing and the logic behind it. Does someone have the actual measurements of the Loar fretboard to compare to a modern fretboard? I was a machinist for many years, and I don't buy into the "wear" theory. I tend to think that the spacing was set intentionally or was set inadvertently when installing the spacers. Either way, it would be interesting to see the actual numbers to compare.

[MikeEdgerton]

So 'presumption' had nothing to do with it other than maybe i was presumptious enough to expect Gibson to use the 'obvious & correct 'machining method - so,point taken !. If they didn't................... ???,

In one of the threads I linked to Bill Halsey suggested that the spacers possibly were just put back in the wrong order after sharpening the gang saw. I wouldn't assume anything with Gibson.

[HoGo]

I managed to find my old measurements of 20's F-4 mandolin board and did some comparisons with perfect tempered scale (12th root of 2 rule). I will try to get hold of some Loar spacings and verify that too.
I calculated fret spacings with rule of 18 (I also tried various figures ranging from 17.817 to 18) and when I used rounding results to 2 or 3 decimals and the final spacing was rounded to nearest 32th of an inch and the plotted errors looks very similar in range and periodicity (with exception of two extremes)
So my guess is thay calculated only two or three digits and the final scale was converted to fractions of inch for convenience.
I would do more math if I had more data... anyone care to measure old board for me?
Also, I heard speculation they used parts of the same loooong gangsaw setup for various instrument boards so knowing other vintage scales would help. Mandola, tenor, guitar... etc Any measuremnts are welcomed!
And last one... What were other common rules for calculating fret spacings in early 20th century?

[Shelagh Moore]

Is Steve Gilchrist working to exactly the same scale length?

[HoGo]

I bet he uses modern precise scale length. 13.85" (approx 13 7/8") scale gives the best approximation of the old board (meaning the errors are balanced around x-axis, sum of errors is minimal)

[Beanzy]

Hi Adrian,
Unfortunately I'm stupidly busy or I would have done an overlay chart in Visio with the ratios placed for comparison.

I've taken a shot of the chart in the appendix to Ross Duffin's book so you can look at those numbers and ratios for the main temperaments. You can see how the 3rd is the real clanger ET in and why many people rejected it as a solution for so long, but we appear to have been able to get used to it as a compromise to avoid retuning as used to happen when people preferred their 3rds more in tune.

obviously when comparing with fretboards it's probably most useful to use the ratios, unless you can get a graduated chart in cents to overlay on them using the Gilchrist board as a reference.

[David L]

I don't see why string height wouldn't change intonation, although very slightly. If nut height remains constant and strings arer raised wouldn't you be stretching the string more at the 12th fret.yes you could move the bridge back but wouldn't that make the first fret note flat, you haven't changed the height there. I know that's the way we set intonation but all intonation is really incorrect and a compromise.

Of course, changing the string height changes the intonation. The point is that the change will be evenly incremental along the whole fret board. Certain frets would NOT be changed more than others.

[HoGo]

Here is new picture. I Photoshopped the picture of Gil board with Loar board to match the typical 13 7/8" scale and measured the Loar board after that. I was able to fit the Gil board to standard pattern to within 0.4 from calculated fret position at worst fret and total error is 0.01mm and used the errors to correct the Loar measurements from adjusted pic (assuming the Gil board was really precise).
The curves of deviation from equal temperament look similar to my eye...

[Billy Packard]

Whew...
Ignorance is bliss.

[Oliver A.]

Whew...
Ignorance is bliss.

Then unconsciousness must be heaven.

[Timbofood]

"I just drive them, I don't know what makes them work"
"Oddball" (Donald Sutherland) from "Kelly's Heroes"