Total String Tension Calculator

[PurplePlectrum]

McDonald Strings has a Total String Tension Calculator that I found very interesting. To my surprise a medium set of guitar strings have slightly more total tension than a full mandolin set. Am I wrong in having the perception that the total tension of a mando set would be more than a guitar?
http://www.mcdonaldstrings.com/stringxxiii.html

[Coffeecup]

Interesting. We often read that one of the reasons that mandolins are harder on fingers than guitars is because of the higher string tension. This calculator shows the opposite.

[Kevin Knippa]

Seems to me that to understand the impact of string tension on your hands, you need to divide the total tension for a string by the scale length of that string.

I also think the setup of the instrument and how hard you grip the neck have more impact on your fingertips than individual string tension. String gauge relative to tension seems to make a difference, too. I know that D'Addario Flattops are tougher on me than say, J-74's, and it's not just because of the higher tension.

[PurplePlectrum]

OK Measuring foot pounds necessary to press a string to a fret wire positioned as close to the center of the string as possible, would be a way of measuring the power you need to fret. (Fretting meaning... NOT the wood but the wire, we give luthiers more fret jobs that way.) Compairing that to a guitar string done the same way would give you an idea weither it is harder to fret a guitar or a mandolin. If you push on a string closer to the nut would it require more ft lbs? Could the total amount of tension on a mandolin be less but the pressure to fret it could that be a different matter?

[PseudoCelt]

If you put in the gauges of a set of J74s, arguably a "standard" set of mandolin strings, the total tension comes out a bit higher than the medium guitar set. You are also pushing down two strings per note on a mandolin, but only one on a guitar (6-string).

I might be wrong, but assuming the action is identical, I think fretting a shorter string would require more force as you are deflecting the string by a greater proportion of its total length, so a mandolin string would feel stiffer than a guitar string.

Patrick

[Bernie Daniel]

PseudoCelt:I might be wrong, but assuming the action is identical, I think fretting a shorter string would require more force as you are deflecting the string by a greater proportion of its total length, so a mandolin string would feel stiffer than a guitar string.

You are exactly right. Think of it as a lever -- the scale (nut to bridge) is the length of the "handle". You have a lot more leverage on the guitar string --its longer.

Best to compare the mandolin with a 12-string guitar-- even with two guitar stings it still requires less force to push them to the fret than a mandolin -- IMO anyway.

It's easy to "bend" mandocello string -- hard to bend a mandolin.

[PurplePlectrum]

I give you guys both a Perfect " 8 "! Ain't Mandoengineering Geekdom wonderful? Now we need an mechanical engineering or testing/instrumentation guru to tell us WHAT the foot pounds on the individual strings would be.

[Spencer]

You can make a first approximation of the force needed to push the string down by multiplying the string tension (T) by the distance to the fret board (H) (action) and dividing by the distance from the string to the nut (L). I've made a little sketch. The "foot pounds" would be the work required to move the string, which you get if you multiply the force required to stretch the string (F) by the distance to the fretboard (H). It's pretty small, otherwise we would get worn out quickly.

The force is probably more interesting, and directly noticable. If you take a 015 A string and a 35 cm (about 13.7 inch) string length, the string calculator website says 19 pounds (8.7 kg) of tension for the string. At the 12th fret, assuming an action of 1,7 mm, the distance to the nut is 17.5 cm, which is 175 mm. This gives a force of about 0.2 pound, or about 0.09 kg = 90 grams). Seems a little high, I'll have to check it when I get home.

For the experimentally inclined, you can find out the force by turning the instrument upside down, and hanging a weight from a string and measuring the deflection. That is, in the case above if the numbers are close, if you hang 0.2 pounds from the string, it should move about 1.7 mm ( about 1/16 of an inch).

Back to the music
Spencer

[OldSausage]

The who d'you ma what?

[Spencer]

Somebody asked for an engineer, and see what you get!

I actually just checked the numbers on my mandolin. With crude measurements, a weight of 107 grams stretched the string about 1.5 or so mm, so it's in the ball park. The distance that you stretch the string when playing really depends on the distance from the rest position of the string to the fret, not the fretboard, so that is the distance H to use in my previous post. The action on mine is such that the A string is about 1.5-1.7 mm above the 12th fret so the 90-100 gram force (0.19 lb) seems about right.

Apologies to the non-engineering types

Spencer

[allenhopkins]

An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
An engineer sees the glass as twice as large as needed to hold the current volume of fluid.

[Tom C]

On a related question with tension.
I have 2 mandos, Same scale, same strings on each. Being tuned to pitch, one feels like there is less tension than the other when playing. Is this possible? Would the angle have any variance? I would think tension = pitch if the strings are the same. It could just be frett wear, action, neck shape..etc.

[PurplePlectrum]

All Hail the engineer! Honestly! I worked with them... Now with a simple test that I can perform on my instruments... guitar, mandolin, bouzouki and b$!.#jo. I will have a simple answer! Question: Which is harder to play or which insturment requires the most ft lbs exerted on the string or the double string. I'll find an answer ...unless someone beats me to it! Then I will read it here first! Now I must teach lessons. To be continued... Oh and thank you for the information!

[raulb]

And then there was Bill Monroe's action! How many mile-tons was that measurement?

As to engineers, I have always said, "anyone can make a mistake but it takes an engineer to really foul it up."

[Coffeecup]

Good information Spencer, thank you.

[Spencer]

On a related question with tension.
I have 2 mandos, Same scale, same strings on each. Being tuned to pitch, one feels like there is less tension than the other when playing. Is this possible? Would the angle have any variance? I would think tension = pitch if the strings are the same. It could just be frett wear, action, neck shape..etc.

The physics say that it takes the same force to move the strings the same distance if they have the same size, length and tension. A first guess would be that one instrument has a slightly smaller distance from the rest position of the string to the fret i.e, lower action. If you don't have to push it so far, you don't need so much force. The factors you mention could all affect the distance you need to move the string to note the instrument, and the differences between the instruments could vary from fret to fret. But what the heck, just enjoy them!!

Spencer