String fretting force measured

[crw]

Just a subjective observation here. It seems easier to me to get a clean note from the low E string than from the high E one. The thin high E digs into my fingertip more as I press on it, making it feel like I'm getting diminishing returns as applied force increases. Perhaps I need thicker calluses...

[DDW]

The big variable is, what kind of break angle does there need to be between your fingertip and the fret, to keep the string from buzzing? This must vary from string to string. Also the amount of damping from the fingertip material could play a role, and this may also vary from string to string: how far that particular string sinks onto the fingertip etc.

I wonder if a more reliable result would be had from using a hard fingertip, made from nut or saddle material, which would eliminate the damping and position uncertainty of a soft fingertip. Pressed against the string it might create a clear tone even before the fret was touched (on a light pluck anyway), but you would know when the fret became the stopping element because the tone would be true to the note.

If it is related to break angle (as I think it must be), then the cos factor in the equation would be the cos of that break angle, not the angle from saddle to fret, and that former angle is necessarily greater than the latter. The angle from saddle to fret only provides for touching the fret - guaranteeing a buzz - not a buzz free tone.

I can envision a fixture that allowed fixing a position on the neck relative to the fret, then a way to accurately push down on the string until the buzzing stopped, and measure that distance and therefore angle. Then move the fixture towards or away from the fret and repeat. I'd expect the break angle to need to be the same, so when further from the fret you'd have to press further down. However the cos would be the same, so the pressure required should be the same.

Except that, when pressing a string between two frets, there are two restoring forces, one due to the tension of the string towards the saddle, and another due to the tension of the string towards the nut. At a given deflection, the two would be equal when exactly midway between them, as you move towards the saddle the angle steepens and force increases on the saddle side, but the opposite happens on the nut side and vice versa. Since the cos function is non-linear, there should be a minima midway between the frets, and increasing equally as you go towards one or the other, leaving exactly one location with sufficient break angle and minimum force required. Which we know from playing.

[Gress]

Originally Posted by Murphy Slaw

This all sounds very familiar...

Thx for the nice song!

[Gress]

Originally Posted by DDW

The big variable is, what kind of break angle does there need to be between your fingertip and the fret, to keep the string from buzzing? This must vary from string to string. Also the amount of damping from the fingertip material could play a role, and this may also vary from string to string: how far that particular string sinks onto the fingertip etc.

I wonder if a more reliable result would be had from using a hard fingertip, made from nut or saddle material, which would eliminate the damping and position uncertainty of a soft fingertip. Pressed against the string it might create a clear tone even before the fret was touched (on a light pluck anyway), but you would know when the fret became the stopping element because the tone would be true to the note.

If it is related to break angle (as I think it must be), then the cos factor in the equation would be the cos of that break angle, not the angle from saddle to fret, and that former angle is necessarily greater than the latter. The angle from saddle to fret only provides for touching the fret - guaranteeing a buzz - not a buzz free tone.

I can envision a fixture that allowed fixing a position on the neck relative to the fret, then a way to accurately push down on the string until the buzzing stopped, and measure that distance and therefore angle. Then move the fixture towards or away from the fret and repeat. I'd expect the break angle to need to be the same, so when further from the fret you'd have to press further down. However the cos would be the same, so the pressure required should be the same.

Except that, when pressing a string between two frets, there are two restoring forces, one due to the tension of the string towards the saddle, and another due to the tension of the string towards the nut. At a given deflection, the two would be equal when exactly midway between them, as you move towards the saddle the angle steepens and force increases on the saddle side, but the opposite happens on the nut side and vice versa. Since the cos function is non-linear, there should be a minima midway between the frets, and increasing equally as you go towards one or the other, leaving exactly one location with sufficient break angle and minimum force required. Which we know from playing.

Exactly my thinking. So yesterday I got myself these to replace the cup I used before.


The advantage of those are three- they are stiffer, smaller and round (which should help with fretting angle).

Here how it looks on the probe now


And this yielded 10% reduction of the fretting force. For instance, for G string it is now .45 lbs


As for your second point, I agree. The size of the larger cup was not helping. With the smaller new one, however, I failed to see a noticeable difference as I moved along the string within the fret. There should be an optimal location, no question, but the difference is small it seems.

Anyway, here are new numbers:
E- 0.47
A- 0.46
D- 0.50
G- 0.45
B- 0.38
E- 0.35

[Gress]

Another thought on the optimal location. Theoretically you want to have horizontal and vertical components of the string resisting forces on both sides from the fretting point to be the same. It would be obviously a point where the string would form the same angle on both sides.
For the 1st fret, e.g., it depends on the height of the nut vs 1st fret[wire].
Assuming the nut is higher, the location for the equal angles then would be shifted towards the fret.


Going along the frets at certain fret number (most likely the 2nd one) the fretted string would lay on the fretwires on both sides. So assuming the height of them the same (or very close) the optimal fretting location would be in the middle of the fret.

All this is for the narrow spot fretting (a point fretting). For the finger or a cup, though it vastly depend on the profile and softness/bone structure of the fingertip.

I believe, this all is second order of magnitude discussion and could be left out.

[Moldstar]

I thought the standard formula for string tension was T = W + ma?

[Gress]

Originally Posted by Moldstar

I thought the standard formula for string tension was T = W + ma?

There are two problems with this.
1. This formula is for gravitational tension only
and more importantly
2. We are talking fretting Force here. Not the tension.

Having said that, having a good formula for the string tension would help.

[TennesseeWalker]

Quite innovative and a fresh approach to an often discussed subject here - I too would like to see the approach developed and refined.

[Murphy Slaw]

I'm digging the drawings.

More drawings.

[Gress]

Originally Posted by Murphy Slaw

I'm digging the drawings.

More drawings.

Ha-ha
Enjoy!

[Gress]

While waiting for the string change on my GPC16e, I got myself a small CF guitar. It is parlor sized Emerald X7. It's a version 2 from 2017.


One of the reasons I got it was to try the one-piece body/neck with the low setup from the factory.

This particular model has a truss rod (as I understand it, to adjust for the player style and strings used rather than other factors like humidity, temperature, etc., as the setup is not changing with those). It came with low setup, but I decided to lower it a bit more and got it down to very low set-up with still enough relief not to buzz.




I am posting this here, as I think it might be interested for the fretting force discussion. This is a short scale 24" guitar. I installed Martin Flex core MA540fx 12-54 strings and the guitar is extremely easy to play. No buzz.

So I decided to compare the fretting force following the exact same methodology as I did for my GPC16e guitar with similarly comfortable setup.

Here goes for the X7:


Emerald X7 with MA540fx:
E- 0.40
A- 0.42
D- 0.50
G- 0.43
B- 0.30
E- 0.27

as compared to the Martin GPC16e (as measured before) with 12.5-55 light-mediums MA545 strings. Here goes again for the comparison:

Martin GPC16e with MA545
E- 0.47
A- 0.46
D- 0.50
G- 0.45
B- 0.38
E- 0.35

So, interestingly enough, although there is a difference obviously, it's much less than I'd expected it to be. Thinner and more flexible strings, shorter scale, a bit lower setup resulted in less than 0.1 lb (and sometimes as low as 0.03 lb) difference.

Perhaps this should put the quest of measuring the differences between the strings to the rest

[Jimbo00]

Love this experiment/test. After reviewing your initial test results, each individual string seemed pretty close to any of the others relative for gauge of string tested. I expected that from a perspective of a uniform set up for string action height. That was always my goal was to get the entire set for the bottom of each string to be the same measurement distance to be fretted. The problem I can see with that is the top of each string is going to be a little wonky for picking & strumming because the strings are different wound & non-wound dimensions. But watching video of set ups (Stew Mac perhaps most notable), the radius gauge is the bottom of the strings to follow the fretboard radius. And that would have that top of the strings going wonky for the top of the strings distances from the frets.

Then when you tested the overall set for a bar press essentially what a capo would need for force across all 6 strings, the 2.96 lbs was darn close to the 2.91 of summing each individual string would need to fret. Pretty accurate. Here's where I struggle with logically analyzing the data. In my head, the bar test is kind of irrelevant, because the capo does the work and for chording at worst 3 or 4 of the 6 strings would ever need to be fretted for a chord. Add that for chording, an individual finger is what is the force required to fret that given string. Can the fretting force be any more than what the most force of any string would require to be fretted ?

String tension makes sense that it's the sum of the lbs of tension as a set, because that's distributed over the area that the strings & guitar as a complete build interact.

End of the day, part of any set up I would ever strive to end up with, is low enough string action height to be easily fretted, yet have a little side to side bending action without being overly floppy & loose feeling, not an excessive note change yet noticeable. The initial down fret is an accurate intonated note, without drifting. And a bend being a note as well for a tremolo/vibrato effect. Maybe the bending is more relative for electric guitars rather than acoustic guitars relative to Boomer Bends.

[Gress]

Originally Posted by Jimbo00

Love this experiment/test. After reviewing your initial test results, each individual string seemed pretty close to any of the others relative for gauge of string tested. I expected that from a perspective of a uniform set up for string action height. That was always my goal was to get the entire set for the bottom of each string to be the same measurement distance to be fretted. The problem I can see with that is the top of each string is going to be a little wonky for picking & strumming because the strings are different wound & non-wound dimensions. But watching video of set ups (Stew Mac perhaps most notable), the radius gauge is the bottom of the strings to follow the fretboard radius. And that would have that top of the strings going wonky for the top of the strings distances from the frets.

Then when you tested the overall set for a bar press essentially what a capo would need for force across all 6 strings, the 2.96 lbs was darn close to the 2.91 of summing each individual string would need to fret. Pretty accurate. Here's where I struggle with logically analyzing the data. In my head, the bar test is kind of irrelevant, because the capo does the work and for chording at worst 3 or 4 of the 6 strings would ever need to be fretted for a chord. Add that for chording, an individual finger is what is the force required to fret that given string. Can the fretting force be any more than what the most force of any string would require to be fretted ?

String tension makes sense that it's the sum of the lbs of tension as a set, because that's distributed over the area that the strings & guitar as a complete build interact.

End of the day, part of any set up I would ever strive to end up with, is low enough string action height to be easily fretted, yet have a little side to side bending action without being overly floppy & loose feeling, not an excessive note change yet noticeable. The initial down fret is an accurate intonated note, without drifting. And a bend being a note as well for a tremolo/vibrato effect. Maybe the bending is more relative for electric guitars rather than acoustic guitars relative to Boomer Bends.

Thank you. For the uniformity of the action string to string, we know it's not the same and it goes lower from E to e. Also with the string diameters being different and with the thickest E string being higher as well, the strings are not equally away from the fretboard, but with the differences being small and the fretboard radius at play it does not make a problem for our hands.

I completely agree with you on the bar test as being just theoretical and almost irrelevant to real life where only few strings indeed need to be fretted.

Finding, as you said, the optimal string height is all different discussion. Some like them low, some not so much. According to a poll I posted on this though dominating 72% of those who replied like the action being less than 3/32" and 82% like them less than 7/64th.

[frankmcr]

My apologies if this has already been mentioned, but one of the most important things to learn for those who want to play the guitar well is to use the absolute minimum amount of pressure against the fretboard. The fingertips do eventually harden, but just learning how to get a clear note with the lightest possible touch is more important.

I think using some sort of mechanical device to push the gauge down with consistent pressure would be better than just somebody pushing it down by hand.

Also, obviously, needs to be done for every fret of every string.

[beninma]

It's super interesting, very nice.

However it doesn't help me when the problem is I somehow press down harder than I need to if it's a difficult chord compared to an easy one!

And it also doesn't stop me from pressing down harder than I need to when the job of my right hand is difficult!

It would be really, really interesting to take some brand new guitars that haven't had a setup and run this test, then do different levels of setup and re-test each to see the difference.

Also testing stock nut height vs optimally lowered would be fascinating if you tested at the first fret.

This stuff is so complex, I think I even change how hard I push down on the strings based on the pick I use or whether I'm fingerpicking. All stuff I need to train out!