Understanding String Tension

Started by admin, December 20, 2018, 03:34:50 AM

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admin

https://www.thegearpage.net/board/index.php?threads/confused-by-my-new-335.2002748/

QuoteI'm not a scientist, but, if you have two guitars with the same strings, tuned to the same pitch, with the same scale length, the string tension will always be equal. No?

No. In a vacuum (let's say a string tied between two nails 24 3/4" apart on a FLAT board), sure, the tension of the string would be the same between any boards you wanted to use. (But...the TONE Wood!)

But, once you start using guitars, all sorts of angles come into play - angle of the neck to body, angles created by the bridge/saddle height, angle of the headstock, etc. Now, the tension of that given string will be applied differently.

Here's a reasonably simple explanation. Basically, as the angle increases, tension (force, really) increases as well.

https://www.engineeringtoolbox.com/rope-angle-tension-increase-d_1507.html




http://www.es-335.org/2011/11/01/the-curious-break-angle/





Shingles

These are important factor but I humbly disagree with the interpretation.
The engineering explanations shown describe an increase in tension of the angled part of the string I.e. the length behind the nut, fret or bridge. The tension of the vibrating portion is not affected.

The resonant frequency (note) of a string depends on the tension, the vibrating length and the mass. Nothing else. So for the same gauge string, same material, same length, same note, the tension must be the same.

The string feels looser because of what happens when one applies a sideways force. The easier it is for excess string to slide over the bridge saddle or fret or nut, or for the bridge to move, the looser the string will feel.
Nik
--------------------------------
Tonelab, VG99, Axon AX100, EDP, Repeater
Godin, PRS, Crafter and Roland guitars
Center Point Stereo Spacestation V3

admin

#2
the height of the tail piece does effect the string tension during string bends.

On a Les Paul with same brand and gauge strings tuned at normal pitch  - There is a difference in string bending torque required when you compare



Normal string install



vs


Top Wrapping

more info
https://www.seymourduncan.com/blog/tips-and-tricks/string-theory-what-is-top-wrapping
QuoteThere are two main reasons that players might employ (Top Wrapping) method of stringing: string slinkiness and sustain.

STRING SLINKINESS
Top-wrapping creates a shallower break angle over the bridge saddle, since the strings pass from the top of the bridge instead of halfway through it, and many players report that their strings feel looser and slinkier as a result. The idea is that with the shallower break angle, the strings are free to move more easily over the bridge when you bend. By the way, as with any setup, it's a good idea to use some kind of lubricant at the saddles and nut slots.

SUSTAIN
Secondly, players report an increase in bottom end and sustain when they top-wrap, and they attribute this to the fact that the tailpiece is screwed right down against the body, creating a more efficient transfer of energy from the string into the body, and from the body back into the string.

I tried this with my Gibson Les Paul Traditional and I definitely noticed an improvement in string bendability, low end and sustain, although this will be more apparent on some guitars than others, on a 'piece-of-wood-by-piece-of-wood' basis. Next string change, consider giving it a try to see if it works for you!


you have a Gibson and pack strings - try yourself by changing the tail piece height as well as try wrapping over the stop tail piece

https://www.thegearpage.net/board/index.php?threads/confused-by-my-new-335.2002748/page-3

Read the comments here - as all strings have a degree of elasticity "the string between the nut and saddle and the string between the saddle and tailpiece can be modeled as two springs in series"

http://www.es-335.org/2011/11/01/the-curious-break-angle/

QuoteChris W says:
November 3, 2011 at 10:53 am
As an engineer, here's my take on it...

The break angle can not effect string tension for unbent strings, period. Charlie's analysis of tension = pitch for a given string construction is correct. The only way that the break angle could effect string tension during bends, is if the angle is shallow enough that the string is allowed to slide over the saddle during bending. In this case, the string is capable of stretching both in front of the saddle, and behind it, which would change the effective spring constant of the string by changing the strings effective length during bends. In other words, the string between the nut and saddle and the string between the saddle and tailpiece can be modeled as two springs in series, where the compliance is additive. If the string can not slip over the saddle, we are back to a single spring model with the compliance being the function of the string construction, length, and tension (i.e. pitch).

With a stop tail, none of this slippage matters much since the distance between the saddle and tailpiece is short, and the second spring in the two spring model is negligible. Also, the break angle is always high enough where string slippage is probably not happening significantly due to the high coefficient of static friction resulting from the high downward force resulting from the vector sum of the tensions in front of and behind the saddle.

On the other hand, a guitar with a short Bigsby and a roller bridge would fit the two spring model better (low friction on the "saddle", long second spring), and I would expect it to feel slinkier bends on that guitar. Another slightly different example of a two spring model is a guitar with a Floyd Rose. Bends are easier on a Floyd because the second spring is complying in addition to the string. And as Floyd players know, there is also the extra effect of the tension being non linear during a bend due to the second spring giving. A string has to be bent further to achieve the same pitch, complicating the analysis some more. Nothing is simple, right?

Regarding tone, any archtop builder will tell you that down pressure at the bridge (a function of break angle) has a strong influence on tone. Stronger down pressure excites the guitar top more and brings more resonance and damping into the sound. In other words, it becomes more of a complex hollowbody sound. The degree of the effect this has on a solid top or a semi hollow is debatable, but it should have some.

And for my last engineering comment: This is easy stuff to measure. If I were really into this stuff and were going to assert or argue it on the internet (I'm just doing thought experiments here), I'd take some force vs displacement measurements as a function of break angle for a few different tailpiece setups. This could be done simply with a luggage scale (simple force gauge).

QuotePeter says:
November 1, 2012 at 11:54 am
I've been playing guitar for 30 years. I'm also an engineer. I own many guitars with stop tailpiece incl. a 335. Adjusting the height of the tailpiece could make a lot of difference, not only to pick attack and how you feel the strings, but also to tone and sustain. This is how it works:

* The break angle depends on the neck set angle, the bridge height and the height of the tailpiece.

* A steep break angle increases the pressure on the bridge. More of the strings energy is transferred to the body/top of the guitar making it acousticly louder but with less overtones and harmonics. The bridge will collapse under pressure over time. Before that it might tilt. Strings break more often.

* If the strings are in contact with the rear edge of the bridge, the tailpiece is to low. This kills sustain

* A steep break angle leads to the dead portion of the string behind the bridge becomes less elastic and therefore makes more resistance when picking near the bridge, or bending strings. The guitar gets a firmer feel, comparable to using heavy strings.

* Guitars with 4+ degree neck angle has a higher bridge than a guitar with less neck angle (but it would also depend on the height of the fretboard and the frets). These guitars would often benefit from a higher tailpiece or even a top wrap in some cases for optimal sustain and a smoother feel.

https://twitter.com/carlos_moreton/status/625286114740469760

QuoteEased the string tension on my Les Paul by stringing over the tailpiece. Great sounding old guitar.

HecticArt

Quote from: Shingles on December 20, 2018, 09:24:00 AM
These are important factor but I humbly disagree with the interpretation.
The engineering explanations shown describe an increase in tension of the angled part of the string I.e. the length behind the nut, fret or bridge. The tension of the vibrating portion is not affected.

The resonant frequency (note) of a string depends on the tension, the vibrating length and the mass. Nothing else. So for the same gauge string, same material, same length, same note, the tension must be the same.

The string feels looser because of what happens when one applies a sideways force. The easier it is for excess string to slide over the bridge saddle or fret or nut, or for the bridge to move, the looser the string will feel.

The logic of what you're saying is perfect in my mind. It totally adds up: the same string length (between nut & bridge), gauge, pitch should equal the same tension or feel.

The structures classes that I took in college tell me that the angles and lengths will create different forces on the bridge, nut, and the lengths of strings beyond them. The tension on "F" should be the constant, and the forces on "F1"' "F2", and "F3" should be the variables that change on guitars with the same scale length.

Physics does, however, tend to surprise me with things that are true that don't seem to make sense.

Shingles

Yes, as I said:

Quote from: Shingles on December 20, 2018, 09:24:00 AM

The string feels looser because of what happens when one applies a sideways force. The easier it is for excess string to slide over the bridge saddle or fret or nut, or for the bridge to move, the looser the string will feel.

But if you are not trying to deflect the string sideways, the tension is unaffected by what is behind the nut or bridge.
Nik
--------------------------------
Tonelab, VG99, Axon AX100, EDP, Repeater
Godin, PRS, Crafter and Roland guitars
Center Point Stereo Spacestation V3

admin

Quote from: Shingles on December 20, 2018, 10:20:18 AM
Yes, as I said:

But if you are not trying to deflect the string sideways, the tension is unaffected by what is behind the nut or bridge.
Agreed

HecticArt

Quote from: admin on December 20, 2018, 09:39:47 AM
As an owner of a dozen Gibsons - and one who always bends strings,  I disagree  - 

the height of the tail piece does effect the string tension during string bends.

On a Les Paul with same brand and gauge strings tuned at normal pitch  - There is a difference in string bending torque required when you compare



Normal string install



vs


Top Wrapping

more info
https://www.seymourduncan.com/blog/tips-and-tricks/string-theory-what-is-top-wrapping

you have a Gibson and pack strings - try yourself by changing the tail piece height as well as try wrapping over the stop tail piece

https://www.thegearpage.net/board/index.php?threads/confused-by-my-new-335.2002748/page-3

Read the comments here - as all strings have a degree of elasticity "the string between the nut and saddle and the string between the saddle and tailpiece can be modeled as two springs in series"

http://www.es-335.org/2011/11/01/the-curious-break-angle/

So the variable isn't really the tension between nut and bridge. It's the friction at the nut and bridge caused by the increased/decreased tension of the bridge/headstock assemblies. When you bend (change the tension of "F") F1,2,&3 come into play and keep the equilibrium of the system....... (Or something like that. I forget the terminology fro structures classes....)

admin

#7
there are many variables at play for determining string tension during bending , and many physics modeling incorrectly forget to model the elasticity of the string , or additional "non speaking" string length correctly

"the string is capable of stretching both in front of the saddle, and behind it, which would change the effective spring constant of the string by changing the strings effective length during bends. In other words, the string between the nut and saddle and the string between the saddle and tailpiece can be modeled as two springs in series, where the compliance is additive. If the string can not slip over the saddle, we are back to a single spring model with the compliance being the function of the string construction, length, and tension (i.e. pitch)."
 

HecticArt

Now it all adds up.
Given scale lengths all feel the same......till you play them.

Elantric

#9
https://web.archive.org/web/20141112202026/http://www.stewmac.com/How-To/Online_Resources/Fretting/Scale_Length_Explained.html

SCALE LENGTH EXPLAINED


Finding your scale length, how it affects tone, and more.

WHAT IS SCALE LENGTH?
A guitar's scale length is calculated by measuring the distance from the front edge of the nut, where it butts against the end of the fingerboard, to the center of the 12th (octave) fret, then doubling that measurement.

If your 1930's Gibson L-OO, for example, measures 12-3/8" at the 12th fret, then your guitar's scale length is twice that—a 24-3/4" scale. For good intonation, the guitar's saddle will be placed so a little extra string length is added. This extra length is called "compensation," and it means the actual string length is longer than its 24-3/4" scale measurement. At the center of the saddle it will be closer to 24-7/8". Compensation varies for different strings, and that's why your saddle is placed at an angle.       

Need help computing or laying out a fret scale? Our online Fret Calculator will do the math as well as help you locate your bridge correctly.
https://web.archive.org/web/20141119000446/http://www.stewmac.com/FretCalculator



HOW SCALE LENGTH AFFECTS TONE

Fender
One of the most common scale lengths is the Fender 25-1/2" guitar scale. Found on Stratocasters®, Telecasters®, and the huge variety of instruments inspired by them as well as the replacement, and custom parts available for them.

The 25-1/2" produces a rich, strong, bell-like tone, and defined low-end.

Gibson
The Gibson 24-3/4" scale is also very common, but it is also the most confusing of all scale lengths—this is because it rarely ever measures out to be 24-3/4 inches! This scale has gradually changed over the past fifty or so years due to changes in production equipment.

Being shorter than the Fender 25-1/2" scale, the Gibson 24-3/4" scale has a lower tension/easier to play feel, and a warmer tone.

PRS, Dobro, & National
When luthier Paul Reed Smith was developing his now highly desirable guitars, he was looking to capture the harmonic richness of the Fender electric's tone as well as the fullness, warmth, and playability of the Gibson electric guitars. PRS opted for a scale length of 25", which is also found on Dobro and National guitars.

The bass strings on a 25" scale are fuller sounding than some 24-3/4" instruments, which can sometimes sound muddy. The treble strings are not only easier to bend than on a 25-1/2" scale, but also have a warmer, and fuller tone.

Elantric

#10

My observations, at age 15  I was fortunate to own  a 1965 Gibson ES-330, which due to restricted upper fret access, as a Lead Guitar player I traded for a 1961 Gibson SG Special which provided easy access to the upper frets.

This was in the late 1960s/  early 1970s when used Gibsons were traded for $200 in Chicago suburbs , regardless of model. ( I mowed many  lawns at $5 per lawn )
By age 19 I acquired a Les Paul and a Stratocaster - much prefered playing the Les Paul for its beefier tone and easier string bending -as I was in Chicago, and playing Mike Bloomfield style guitar was required to get work. As a result Ive developed Decades of muscle memory from playing on dark dimly lit stages with my Gibson guitars reinforce my preference for 24.75" scale length guitars.

Now that Im older (69)  I find Fenders in standard A 440 hz tuning a bit stiff for string bending , and bent string riffs with vibrato I pull off easily on my 24.75" scale Les Paul, require more effort and concentration to duplicate  on my 25.5" scale Fender guitars. Couple that with senior hand /muscle ailments has me reassessing the guitar I play on stage with my current band , often play 4 hour gigs.

The PRS is a 25" scale and closer to the Gibson experience,  but as I get older - either I tell the Bass player to tune down to Eb - so I can play my Fenders tuned down to Eb, or just start playing my 24.75"  Gibsons again as main guitar to continue my active live performance  music career
https://www.vguitarforums.com/smf/index.php?topic=6125.450#msg269199