String fretting force measured

[Gress]

Originally Posted by Sev112

This is the best thread I’ve read in ages Bravo

Am so tempted to get one of those gauges

Thank you.
This all came from my newly found love for the Martin's MA545 with the gauges exactly in between the lights and mediums. They go 12.5, 16.5, 25.5, 33.5, 43.5, 55

It's amazing what a great sounding strings / guitar combo can do to us. Some may even go through a refresher on physics

[Jimbo00]

What is the guitar open tuned for ? That's going to change relative for the tension of the strings for tuning, the fret that is depressed & string gauge. Neat little device.

[Mr. Jelly]

Now we have a new rabbit hole. Hang on!

[Gress]

Decided to do a quick formula calculation.
Was too lazy to do exact Young's modulus research, so found this

I decided to use 200. As we will see later, id does not matter.

Then found the tension data


Then measured the string length (the distance from the saddle to the 3-rd fret location I used to fret the strings

it is 55cm or .55m

Then measured the G string height above the 3rd fret and it is 2.3mm or .0023m

Then I averaged the tension data for my strings which are in between the light and medium.

Then I did a quick calculations:


If you reading the calculations, please note that due to the Alpha angle being very small, the formula is much simplified.

Unfortunately, it does not work.

I calculated the Fretting force for G string and calculated the adj. coefficient to match measured .49 lb.

Then using Tension data for e string and B strings I calculated adjusted force for those and they did not match the measurement.

Perhaps the formula I found on the electric guitar forum is incorrect, or the tension is incorrect etc.

BTW, if you look at the tension data, you will see that tension for B string is less than tension for e string, while the force is proportional to the tension according to the formula. That means that B string force should be less than e string force, which itself contradicts my measurements.

[Sticky_fingers]

Good thread and idea, but pounds?

[lar]

FYI - These are also available in case others want a cheaper option. Very basic, uses a spring where the Mxmoonfree probably uses an electronic load cell. They don't give accuracy data but sensitivity data should be valid:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It would be interesting to determine the push sensitivity to string action (height). For example, if you lowered E action from .1" to .09", how much would the push force decrease? You could potentially do this without adjusting the actual action on the guitar by placing thickness gauges on top of the fret.

[Gress]

Originally Posted by Sticky_fingers

Good thread and idea, but pounds?

You prefer Newtons ?

[DDW]

Why not Stones?

What I'd like to measure is the change in fretting pressure going from high tension to medium or low tension (this is on nylon), also standard tuning vs. a half or full step down, also high frets vs. low frets.

I'm not sure I am following your calculations correctly, but if it is showing a G string tension of ~32N, 7 lbs, that seems far too low. I'd believe 32 lbs maybe. Even nylon strings are around 14 - 17 lbs.

[Sir strumalot]

Originally Posted by Gress

Decided to do a quick formula calculation.
...
Perhaps the formula I found on the electric guitar forum is incorrect, or the tension is incorrect etc.

BTW, if you look at the tension data, you will see that tension for B string is less than tension for e string, while the force is proportional to the tension according to the formula. That means that B string force should be less than e string force, which itself contradicts my measurements.

Seems complicated to me. If you assume the string doesn't stretch significantly (so the intonation is good) then you could ignore Young's modulus etc. Near the nut the angle from fret to nut is close to zero, so you're left with a force of Tsin(alpha). Measuring my guitar, the 3rd fret is 550mm from the bridge, action at 12th is 2.5mm, so 5mm at the bridge. So sin(alpha) is 5/550, with a tension of 30(pounds?) that gives a fretting force about 0.25 That just gives the force to push the string to the fret, not the force to stop it buzzing - I don't know how you could calculate that.

[rick-slo]

Many factors in playability including fret height, width and crown shape - for example somewhat paradoxically quite low fret height is a problem in an effort to play cleanly.
Then how far fretting finger is from fret (even in the photos shown there is a significant diffeerence). Etc...

[Gress]

Originally Posted by DDW

Why not Stones?

What I'd like to measure is the change in fretting pressure going from high tension to medium or low tension (this is on nylon), also standard tuning vs. a half or full step down, also high frets vs. low frets.

I'm not sure I am following your calculations correctly, but if it is showing a G string tension of ~32N, 7 lbs, that seems far too low. I'd believe 32 lbs maybe. Even nylon strings are around 14 - 17 lbs.

Thank you DDW.
My tension data is from this

averaged for the light-medium 12.5 set I use.

It's great you posted, as I assumed (perhaps wrongly) that the units used in the table were Newtons (as this is common SI unit for tension). You confirmed with your knowledge then that the table is in pound force. So T used should be left at 32.7 and the F for G string calculated by the formula then of 0.137 Lb.

However, due to the linear dependency on T, it would only affect the adj.coefficient to meet measured force of 0.49 Lb (k=3.554 now) and would not affect overall results and mismatch of the the formula vs measurements.

[Gress]

Originally Posted by Sir strumalot

Seems complicated to me. If you assume the string doesn't stretch significantly (so the intonation is good) then you could ignore Young's modulus etc. Near the nut the angle from fret to nut is close to zero, so you're left with a force of Tsin(alpha). Measuring my guitar, the 3rd fret is 550mm from the bridge, action at 12th is 2.5mm, so 5mm at the bridge. So sin(alpha) is 5/550, with a tension of 30(pounds?) that gives a fretting force about 0.25 That just gives the force to push the string to the fret, not the force to stop it buzzing - I don't know how you could calculate that.

This is exactly what I did and the formula I used.
Please see circled in red.



The only thing that is different is that I introduced the K multiplier to meet the measured force for G string in a hope that then the formula results for the other two would also meet the measurements. Unfortunately, they don't.

P.S. and the biggest issue is that my measurement shows B string force of 0.44 Lb i.e. higher than the e string force of 0,41 Lb while T from the table shows LOWER T for the B string vs e string. So that means that either the T table is incorrect, or the formula could not be linear for T, or my measurements are wrong (which I do not think).

[lar]

Where does your G-string tension of 7.35 lbs come from? Is that supposed to be a normal G-string tuned to pitch w/o fretting it?

Keep in mind that your gauge accuracy is +/- 0.11 lbs: 1% of full scale.

[Gress]

Originally Posted by lar

Where does your G-string tension of 7.35 lbs come from? Is that supposed to be a normal G-string tuned to pitch w/o fretting it?

Keep in mind that your gauge accuracy is +/- 0.11 lbs: 1% of full scale.

It came fom me (obviously wrongly) assuming that the tension data I used was in Newtons. I already answered this
https://www.acousticguitarforum.com/...9&postcount=26

On the accuracy, my accuracy of measuring is worse than that

[Murphy Slaw]

This all sounds very familiar...