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Author
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Topic: scale length and string tension
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Karlis Abolins
Member From: Burien, WA, USA
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posted 29 April 2006 07:55 AM
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While doing some calculations on string gauges for the pedal steel that I am building, I discovered that a small difference in scale length has a significant difference in tension. My guitar has a scale length of 24.25". Using common string gauges I found the following values for 24", 24.25" and 25". I used a spreadsheet developed by Terry Downs that I downloaded several years ago.
24 inch scale
0.01200 F# 26.094 G# 32.877
0.01500 D# 28.830 E 32.361
0.01100 G# 27.626 A 31.009
0.01300 E 24.307 F# 30.625
0.01800 B 26.153 C# 32.951
0.02200 G# 27.626 A 31.009
0.02600 F# 25.360 F# 25.360
0.03000 E 26.798 F 30.08024.25 inch scale
0.01200 F# 26.641 G# 33.565
0.01500 D# 29.434 E 33.039
0.01100 G# 28.204 A 31.658
0.01300 E 24.816 F# 31.266
0.01800 B 26.701 C# 33.641
0.02200 G# 28.204 A 31.658
0.02600 F# 25.891 F# 25.891
0.03000 E 27.359 F 30.710 25 inch scale
0.01200 F# 28.314 G# 35.674
0.01500 D# 31.283 E 35.114
0.01100 G# 29.976 A 33.647
0.01300 E 26.375 F# 33.230
0.01800 B 28.378 C# 35.754
0.02200 G# 29.976 A 33.647
0.02600 F# 27.518 F# 27.518
0.03000 E 29.078 F 32.639
a quarter inch increase in string length yields a half pound increase in tension. a one inch increase yields almost a two pound increase in tension. I always felt that the strings on my current guitar, which is also 24.25" scale length, felt tight. I now know why. Karlis[This message was edited by Karlis Abolins on 29 April 2006 at 07:59 AM.] |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 08:26 AM
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quote:
a quarter inch increase in string length yields a half pound increase in tension. a one inch increase yields almost a two pound increase in tension.I always felt that the strings on my current guitar, which is also 24.25" scale length, felt tight. I now know why. Karlis
Karlis, that is the beauty of a keyless. You can have a 25 inch scale, with less tension and string breakage than with a keyed 24" scale. The extra 3-4 inches in front of the nut on a keyed guitar MUST to be included in the string length. Thats is just the way it is. A keyed guitar will break more strings than a keyless. Period. So, one can get used to changing the the 3rd string frequently or go keyless. Simple.  ------------------
I'd rather be opinionated, than apathetic! [This message was edited by Curt Langston on 29 April 2006 at 08:36 AM.] [This message was edited by Curt Langston on 29 April 2006 at 08:37 AM.] [This message was edited by Curt Langston on 29 April 2006 at 08:39 AM.]
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Fred Shannon
Member From: Rocking "S" Ranch, Comancheria, Texas
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posted 29 April 2006 09:27 AM
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Curt, with all due respect, Horse Crap!! I don't play a keyless, change strings very infrequently, and haven't broken a third in over a year. And that's playing 3 and 4 gigs a week, plus I use the cheapest strings money can buy. Maybe it's the guitar characteristics and how it's made. 
Phred------------------
"From Truth, Justice is Born"--Quanah Parker-1904
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Karlis Abolins
Member From: Burien, WA, USA
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posted 29 April 2006 09:48 AM
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Curt, When a .011 gauge string is stretched between a bridge and nut 24 inches apart so that it reaches a G# pitch, the string has a tension of approximately 27.6 pounds regardless of the length of string beyond the nut. If you do the same on a 25 inch scale, the tension is approximately 29.9 pounds.
The discussion of keyed versus keyless has little bearing on the scale length relative to tension.Karlis[This message was edited by Karlis Abolins on 29 April 2006 at 09:49 AM.] |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 10:18 AM
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Karlis, are you saying that the part of the string behind the nut has no tension? There is about 3-4 inches there.(even more on the 5th string) The strings are anchored at the keys. When you pull from the changer end, you are pulling the 24" or 25" scale, PLUS the amount of string behind the nut. So, basically you are pulling more than 24" or 25" of string, which is why keyed guitars are more prone to string breakage.Next.
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Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 10:21 AM
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quote:
The discussion of keyed versus keyless has little bearing on the scale length relative to tension.
Scale length relative to tension are major factors in string breakage.
 [This message was edited by Curt Langston on 29 April 2006 at 10:23 AM.] |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 10:34 AM
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My friend Michael puts it into perspective.Michael Johnstone
Member
From: Sylmar,Ca. USA
posted 03 December 2002 10:21 AM profile send email edit
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The strings are easier to change - and just about all keyless guitars are something like this - you just hook the string on at the changer end and bring the other end up and wrap it around a small allen head bolt about 1/2 wrap,tighten down the bolt,bend the excess string back and forth a couple times to break it off and the string is on. Then you tune up the string either with the same allen key you used to tighten down the bolt or like on my Sierra and also GFIs work like this - you can tune the string with your fingers using little knurled buttons which look like the fine tuners on a violin. If I break a string onstage,I can have a new one on and be playing again within a verse and a chorus.As far as scales lengths go,most keyed guitars max out at 24.5" before you run into excessive string breakage because the section of string under tension(changer to tuning post)is as much as 27" on the middle strings of a keyed guitar.Conversely on a keyless design,say on a 25" scale,the section of string under tension is only 25" in total. So there is actually more tension on most of the strings on a keyed 24.5" guitar than all the strings of a keyless 25" guitar. Less tension means less string breakage and a shorter pedal pull/string stretch to achieve a given pitch change - so strings last longer and don't break nearly as much.Plus all the strings are the same length with no overhang past the roller nut which translates into zero unwanted overtones that many keyed guitars display and most guys damp out with foam rubber or plastic tubing.Not to mention that harmonics are easier to get,high register stuff is easier to play in tune and the tone is just fundamentally more pure and phat.Lightweight - compact - stays in tune for months - you can't knock it out of tune just by taking it out of the case - it's just a better design from every angle you want to talk about. C'mon guys - On with the future!
-MJ- |
Donny Hinson
Member From: Balto., Md. U.S.A.
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posted 29 April 2006 11:09 AM
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I've never owned a keyless, and I've played one only a couple of times. That said, a lot of what I know I learn from observation and from listening. Over 90% of the top-level pros, both old and young alike, use keyed guitars. These players make their living playing, and they can afford to buy whatever they like. Likewise, they wouldn't use something that was clearly inferior because their livlihood is at stake. So, if there was any significant advantage to keyless guitars, in either convenience or sound, what do you think that 90% group of pros would be playing? Bingo.  |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 11:44 AM
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They would be playing whatever guitar that is given to them. |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 12:08 PM
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Most of the people who "do not like a keyless guitar", have never owned one. It "looks" different to them. Well, it is different. Better IMHO. When a player is enlightened to the advantages of a keyless system, they often wonder why they were hesitant in the first place.
What gets me is that Carter and other very fine brands will make eleqant woodgrain finishes with fine inlays, great mechanics on the underside, then put a low tech, keyed head on it!  [This message was edited by Curt Langston on 29 April 2006 at 12:13 PM.] |
Ricky Davis
Moderator From: Spring, Texas USA
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posted 29 April 2006 12:28 PM
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Yes the amount of tension will vary between scale lengths and string guages....>but the discussion of string breakage has EVERYTHING to do with the amount of tension a given pedal steel takes to pull the string. The pivot positions of the finger and how it's pulled underneath and what is pulling it and the amount of flex give or take and the freedom of the movement> creates the tension on the string when pulled: then where the string is tied down and it's movement of when it's pulled is last; in the calculations of how long a particular string may last before it gives way.
Thems my take on it.
Ricky
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Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 29 April 2006 01:07 PM
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quote:
Buddy Emmons
Member
From: Hermitage, TN USA
posted 08 January 2005 09:54 AM profile edit
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Carl,
In reference to your earlier post, my only experience with the 25” scale other than the Sierra was when Shot Jackson and I were building Sho~Buds. It was during the time the high G# was added to the tuning that we encountered the string breakage problem and had to reduce the scale 24 ½ inches.
To be different than Sho~Bud and possibly reduce string breakage even more, I had fifty 24 ¼” Emmons atom fret boards made in Nashville and gave them to Ron to use on the first guitars. By that time, the Sho~Bud fret board had proven that the longer scale didn’t work so there was no need to experiment with the Emmons guitar. Ron had built a Sho~Bud clone prior to my meeting him and may have been referring to that guitar, but the Emmons guitar started at 24 ¼” and stayed there.Billy… Regarding the topic, I prefer the keyless sound. Jeff Newman had a great sounding Kline keyless S-12 he used during seminars he and I held. We had just finished playing a phrase for the class and while they were absorbing it, Jeff smiled and leaned over and said, “Why does my guitar sound better than yours?” His Kline did have a cleaner sound but I wasn’t about to admit it so I replied, “Because you have a tin ear.” His face flushed and all he could do was force a chuckle. It was one of the few times I ever saw Jeff at a loss for words.
Donny: I guess BE is in that minority of the 10% that like the advantages of keyless technology! |
David Doggett
Member From: Philadelphia, Pennsylvania, USA
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posted 29 April 2006 03:32 PM
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Some people think keyed guitars have better sustain than keyless. This is based on ear impressions, but there is a theoretical reason for this. As the string vibrates back and forth in front of the nut (between the nut and bridge), it will be able to do this more freely if it can move in the opposite direction behind the nut, so that there needs to be less flex at the nut. Therefore, a long length behind the nut aids in sustain. Keyless guitars could be built with any length desired behind the nut, but are usually kept short. However, this is all theoretical. I don't know if anyone has tested this theory.With regard to length and tension. For a given pitch, it is desirable to maintain the same optimum tension, regardless of the neck length (the optimum tension is for the longest pull on the string, not the open string). For a longer neck you maintian optimum tension by using a smaller gauge string. Smaller gauge strings have better sustain. Thus, longer necks have better sustain, as long as you use smaller strings and the same tension. Using the same gauge string and greater tension causes string breakage problems, because you are no longer using the optimum tension. When you go to a shorter than normal neck, you have to use thicker gauged strings to maintain optimum tension, and this hurts sustain. The three neck lengths of the Fender Stringmasters illustrate these tradeoffs well. If you try different neck lengths, but keep the string gauges and pitches the same, the tighter tension on the longer neck will feel more solid and sound louder, but you are inviting breakage problems. I'm not sure what effect this will have on sustain. A potential problem with the high G# on a longer neck is that going to a smaller gauge string might take you to a string that is just too small to avoid breakage, even at the optimum tension. But there have been some long neck pedal steels that seemed to work, so this may not be a real problem. |
Robert Leaman
Member From: Murphy, North Carolina, USA
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posted 29 April 2006 03:41 PM
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For those who think that string length between the nut and the tuners does not affect string tension, why in God's name do all the diehards want roller nuts? There is NO differential tension component across the nut. I have owned many different pedal steels including an infamous Emmons push-pull, but nothing has performed as well as my Sierra Session 2000 gearless D10, 8+7. As always, only MY opinion counts with me. |
ed packard
Member From: Show Low AZ
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posted 29 April 2006 07:22 PM
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KA: Right you are re the tension if you accept the equation as valid...it is quite close re plain strings, but if you measure the tension on the plain strings, it will be different from the simple equation results...think core size among other things.My 14 string neck length is 30 inches, but tuned to C (not E)...same gauges as for E). My total string length is about 31.5" end to end. I will place the sustain (measured, not imagined) against any other instrument out there...that does not necessarily mean that it will sound "better" to those used to other sounding instruments. We (Jim P) and I did 32 different instruments up re materials, dimensions, and so forth. These were also profiled for generated frequency spectrum vs. time (= sustain). Very interesting results!!! Ask Jim P. For "tension vs. string length", the usual calculation is to input the nut to bridge length of the string, the dia of the string, and the frequency...any clamping effect, and stretched string length is ignored. String stiffness is ignored. The amount of thinning (diameter reduction) of the string due to stretching is ignored. The added length of the string due to vibration is ignored...but the results are close enough for "hot jazz". The same tension is on the string between, and beyond the scale length, but the calc is for the frequency of the scale length (nut to bridge). My apology to the anti-tech sector.[This message was edited by ed packard on 29 April 2006 at 07:23 PM.] |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 30 April 2006 02:59 AM
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quote:
The same tension is on the string between, and beyond the scale length,
That is what I am referring to as well. Each guage of string will take X amount of tension for the required pitch. The longer the string is that is being pulled up to pitch, the more tension you will need. The greater the tension on any given string, the closer you are to the breaking point. My point was this: keyless guitars do not break as many strings as keyed, simply because they are shorter from anchor to anchor.[This message was edited by Curt Langston on 30 April 2006 at 05:28 AM.] |
Donny Hinson
Member From: Balto., Md. U.S.A.
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posted 30 April 2006 05:29 AM
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quote:
Donny: I guess BE is in that minority of the 10% that like the advantages of keyless technology!
And yet, what is his newest guitar?!
Click here!
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Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 30 April 2006 05:32 AM
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A FREEBIE! He will probably have to have that picture on the site for a year(or whatever the "agreement" was) I would venture to guess that even the "top of the line" players have budgets to stay with. Just because they can play the steel like no buddy's business does not mean they can afford to buy a new guitar every year.
Times are tough. An edorsement deal on a guitar can appear very lucrative!
Who really knows what a Pro will play in his recording session or at home for pleasure. Often times it is not the one he is pictured sitting behind on a promo ad!
[This message was edited by Curt Langston on 30 April 2006 at 05:51 AM.] |
Erv Niehaus
Member From: Litchfield, MN, USA
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posted 30 April 2006 07:03 AM
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As a kid, I used to have to catch a chicken and chop of its head for Sunday dinner. Some how, a keyless guitar reminds me of a headless chicken.  [This message was edited by Erv Niehaus on 30 April 2006 at 07:04 AM.] |
ed packard
Member From: Show Low AZ
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posted 30 April 2006 07:27 AM
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Erv...I felt the same way about the Steinberger bass. We like to see, and hear, what we have been used to...slows down progress. I bet very few would have bought todays shape autos in the 30s.Curt...lets see if we are on the same wavelength: Two instruments, both 24.25" scale length, one keyed and one keyless...both have 0.011" dia G#s. would
you say that they both have the same tension or not? I say that they do. Just in passing, for a given string material and process, the cross sectional area (CSA)is the limiting factor for that strings tensile strength. The 0.011" dia string is the worst offender by far. a 0.0115" of the same material and process has a MUCH larger cross sectional area. For the Universalists, the next worst pest is the ninth string, if you pull it from B to D. A smaller core will usually mean more breakage from continuous tension changes, and worse if it has a sharp bend in it. |
Karlis Abolins
Member From: Burien, WA, USA
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posted 30 April 2006 08:03 AM
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Curt, I hope that you don't feel that my response to you was meant to disparage your preference for keyless versus keyed. There are several reasons why keyless is a better technology but string tension is not one of them. I have owned a keyless guitar. The only issue I have with keyless is the pretensioning required on most keyless tuners when changing strings.However, my post really addressed the the issue of scale length versus tension. How many people own guitars with 24.25, 24.5, or 25 inch scales and use string sets designed for a 24 inch scale? I think excessive string breakage on longer scale guitars may be due in part to the increased tension on those strings. Ed, Thank you for you comments. You make a valid point about the calculations and wound strings. Terry Downs' spreadheet adjusts for wound strings but recommends an approximate adjustment if the core diameter is unknown which is the case in my calculations. I ran a string set based on the key of C and a scale length of 30" through my spreadsheet and got the following values.
tuned to C and 30" scale
0.01200 D 25.685 E 32.361
0.01500 B 28.378 C 31.853
0.01100 E 27.192 F 30.522
0.01300 C 23.925 D 30.144
0.01800 G 25.743 A 32.434
0.02200 E 27.192 F 30.522
0.02600 D 30.144 D 30.144
0.03000 C 26.378 C# 29.608
Very interesting. In the case of my guitar, I will be shortening the scale length by 1/4". Karlis[This message was edited by Karlis Abolins on 30 April 2006 at 08:06 AM.] |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 30 April 2006 08:23 AM
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Hi Ed.
quote:
Curt...lets see if we are on the same wavelength: Two instruments, both 24.25" scale length, one keyed and one keyless...both have 0.011" dia G#s. would
you say that they both have the same tension or not? I say that they do.
Well, my point is this: The keyed guitar has a longer anchor point(at the key),whereas the keyless head has a shorter anchor point.(usually at least 3 inches) So, the keyed guitar's G# will have to travel farther(with more tension) to raise up to pitch, as the string itself rolls on the roller nut(increasing the resistance). Thus, the keyed guitar will have an increase in string breakage, and MAY be prone to returning a little sharp.
Both guitars should have equal tension when picked open, but as you know, the keyed guitar has more moveable string length to raise.
So, the keyed guitar has to stretch at least 27 inches of string up to pitch, while a keyless has only about 25.25"
Hence the results in less string breakage on a keyless.
The longer the points between the changer and keys, the greater length needed(and tension) to pull to pitch, and the more string breakage.(assuming we are talking about standard E9th tuning)
BTW,I would assume The Beast's (keyless) 30" scale with a lower tuning has very little string breakage problems. But if you tried tuning it to E9th, you probably could not keep strings on it!
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ed packard
Member From: Show Low AZ
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posted 30 April 2006 10:04 AM
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Curt...lets do the details (where the devil is):1.The string (lets use the G# = 0.011" or so)is anchored on one end, usually the ball, to the changer. The other end is anchored to the tuner device. 2. The tuner device does the stretching when tuning...best reason for the roller. The changer end does the stretching/unstretching while playing because of pedal/lever activation. 3. The string end at the tuner device does NOT move when the Changer is activated. 4. If we assume a 24.25" scale length (nut to bridge), a 0.5" distance from ball to top of changer finger, and a 1.0" distance from nut to tuning device we have a total string length of 25.750". 5. The 0.011" G# stretches about 0.04" for a raise from G# to A (measured with 50 pound digital fish scale, digital calipers, and Peterson tuner). That is the total amount for the total string. The changer end (ball) moves 0.040", the tuning device end moves 0.0000" 6. A point half way up the total string length will stretch 1/2 of the total string stretch = 0.020" in this case. A point on the string at the nut will stretch 1/25.750ths of 0.040" = 0.00155"...not much. Begs the question "after you have tuned, what good does the roller do"? 7. If the G# was 6 inches longer because of keyed tuners (surely not the case), it would
be 24.25 + 0.5 + 7 inches total length = 31.750". The point at the nut/roller would then stretch 7/31.750ths of 0.04" = 0.00756"...still not a lot, but the changer end still stretches 0.040". This last is an absurd worst case as G# = string 4 does NOT extend 7" from the nut to the tuning key device. 8. The G# = 0.011" has by far the longest stretch for a half tone raise, so all other strings will stretch less for the same raise. Some of the lower strings may stretch as little as 0.005" for the same raise. 9. On the BEAST, I have moved ALL the after tuning motion to the players left (beyond the bar), and have no sharp bends on the strings. You are right, if I were to tune the BEAST to E strings would be a problem, but if you run the calculations for string tension on the BEAST's 30" neck you will see that the tension is actually one halftone lower than for the 25" scale E9 tuning...less breakage still! Somebody check the arith'. Questions:
Does keyless really need a roller?
Why is the changer on the players right?
Why are the changer and the tuner separate devices?
Is the answer to the above Q's tradition? Again, apologies to the technically disinclined. |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 30 April 2006 11:39 AM
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Hi Ed!Your calculations are impressive. The only thing I disagree on is: quote:
3. The string end at the tuner device does NOT move when the Changer is activated
It does move. Even though it is a minute amount, it is still enough to make a difference.
Consider the problem of strings not returning to pitch after being pulled.(assuming that there is no problem at the changer end.)
Yes, the strings on a keyed guitar are pulled across the nut(even a minute will matter) Because even at 3-4 inches of string in the keyhead, that is enough to allow elasticity in the strings of the keyhead. Which in turn can cause strings to return sharp.
That is why most keyed guitars are not longer than 24.25-24.50
The stretching of the keyhead portion of the strings cause string breakage.
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ed packard
Member From: Show Low AZ
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posted 30 April 2006 12:54 PM
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Curt...You are correct that the portion of the string between the tuner device and the nut DOES move, but the string END at the tuner device does not move...the problem is not that we disagree, but that we see the words used as a different picture....fun anyway.The point of 3. was that the stretching is induced by the changer, and reduces along the string length to zero at the tuner device anchor point (not at the nut/roller). While we are on the nut/roller, are large dia rollers better than small? Are small axles better than large? Are V grooves better than U grooves? Wound strings should tend to "jump" more on small rollers because of the winding spacings. Roller materials that "dent" (Brinnel) from the windings can be a tuning return problem. Sticktion (not friction) between the roller axle and the roller is an issue. This stuff goes on forever. |
Curt Langston
Member From: ***In the shadows of Tulsa at Bixby, USA***
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posted 30 April 2006 12:57 PM
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quote:
The point of 3. was that the stretching is induced by the changer, and reduces along the string length to zero at the tuner device anchor point (not at the nut/roller).
Yes, we do agree after all!
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