Strings Measuring String Tension

70sSanO

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For most people this has no value. But I have wondered if there was an inexpensive way to measure individual string tension. There are very expensive measuring instruments that are available but the cost is so prohibitive.

Racquet string tension gauges, for tennis, are too far out of the ukulele string tension range to be useful. But I saw one for badminton racquets that I thought might work. And for $20, there was little investment. There are multiple sources for the same gauge and they all come from China. I bought one off of eBay. Here is what they all look like...
https://www.badmintonbay.com/Abrz-Tension-Tester-AZ-TT100.html

I received the tester and my opinion is mixed. Since it is two prong device, it is hard to know if tension is being measured, or if string compliance is also a part of the measurement. The accuracy of the tester is not even close to reality. Following the instructions, I'm getting readings around 15lbs on a tenor A string tuned to G#. That might be a result of string gauge and material differences between badminton, and string attachment, versus and ukulele strings along with bridge to tuner length.

The only saving grace is that it does seem to measure a comparative difference between same scale ukuleles with the same and difference strings tuned the same. I can't address day-to-day consistency at this time.

But, the reason I bought it was to address problem strings; for me they are typically C and A. I am hoping that taking measurements on an existing string and then on the replacement, after it has settled, might shed some light. Worst case it ends up being an exercise in futility without much of an investment.

John
 
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Hi John

The measurement for string instruments is end tension which is different from side tension used to check if tennis racket strings are losing tension.

End tension can be:
  • calculated indirectly using formulas, often imbedded in computer calculations apps
  • measured directly using a variation of monochord.


Interested persons could:
1. Build a basic monochord test frame, or
2. Make a jig that that measures string tension from the the loose end of each string at the bridge end of a ukulele or guitar, or
3. Build a simple monochord instrument or pseudo instrument for fun. Use it with a jig to measure string tension.


Method: Attach an electronic tuner to determine when the string is stretched to pitch. Add weight or tension until the musical note is achieved. Record the amount needed to tune each string:
  • Set of graduated weights added until in tune, or
  • Add materials to a bag until the string is in tune. Marbles, pea gravel, dried beans, rice, etc. Weigh the bag and materials on a kitchen scale, or
  • Attach a stretch style luggage scale or fishing scale. Tighten a tuning peg until stretched into tune. Or move the free end of the scale between a series of nail heads until stretched to approx tune. Read and record the tension for each string in tune.


1. Example of basic monochord test jig.

===> The first picture is relevant:

2. Test rig at the bridge end of ukulele or guitar:
  • Measure string tension using weights or a stretch gauge attached to each instrument string before it crosses the saddle.
  • Build a simple frame so the string pull clears the instrument but rests on the saddle for correct string length. Perhaps a four sided open box thingie snugged up against the butt end?
  • Tie or bungee the jig and instrument to a solid surface to avoid movement and accidents.

3. Build a monochord instrument:
- Search ‘monochord’ on YouTube for examples.

Happy adventures…
 
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Pardon the slight swerve away from the subject of string tension, but the OP triggered a memory and now it's bugging me so here I am. Some time in the recent past, I saw photos of some sort of useful tool someone had designed. The tinkerer had attached at least 2 if not 4 side-ear-type geared tuning machines to opposite ends of a narrow board. It definitely was a tool that accomplished some task and was not a primitive musical instrument. I recall immediately wanting to build myself one but now I don't recall where I saw it (maybe here at UU Forum?) or what it was used for. If this rings a bell, please either post or PM.
 
@casualmusic, thanks for your write up.

Yes I agree that string deflection doesn’t measure actual stringing tension between saddle and nut at a particular pitch.

I was suspicious that the deflection readings I am getting are incorporating string elongation beyond the saddle and nut. In a sense I am getting a string compliance value.

For what I am doing, I don’t care about the actual string tension. What I’m concerned about is being able to arrive at hopefully a “useable” comparison of two strings on the same instrument.

If one mfg sells a high tension string that is within that mfg’s own line. There is no quantifiable way to compare it to another mfg’s string; short of building a testing stand.

The theoretical online string tension calculators have no company proprietary information of tue different strings to make an accurate comparison.

I can already guess that the tension of this or that string feels higher when lifting it out of the nut. I’m hoping this gives me another data point so using a high tension string that .001” thinner in diameter for a C string removes the thud but maintains the sound I’m looking to get.

John
 
String tension depends on how much you tension it.

There is a formula to calculate the dependencies of mass, tension and frequency.
If you can weight the string precisely, or know the density and diameter, you can calculate what the tension is at a given frequency.

If you know the mass of the string, you can technically calculate the tension based on which tone comes when you pluck it.

Anyway, you will need a ridiculously precise scale and a long piece of string to determine it.
 
String tension depends on how much you tension it.

There is a formula to calculate the dependencies of mass, tension and frequency.
If you can weight the string precisely, or know the density and diameter, you can calculate what the tension is at a given frequency.

If you know the mass of the string, you can technically calculate the tension based on which tone comes when you pluck it.

Anyway, you will need a ridiculously precise scale and a long piece of string to determine it.
Lol! Yeah, I have to agree that a 2 prong plastic dial is anything precise.

This more of a fun experiment that may or may not amount to anything.

John
 
String tension depends on how much you tension it.

There is a formula to calculate the dependencies of mass, tension and frequency.
If you can weight the string precisely, or know the density and diameter, you can calculate what the tension is at a given frequency.

If you know the mass of the string, you can technically calculate the tension based on which tone comes when you pluck it.

Anyway, you will need a ridiculously precise scale and a long piece of string to determine it.
The calculations and tables are fine. But this thread is interesting as in science we like the experiment to confirm the calculated theoretical values. So I really hope that some brave soul will rig something up and give us some data to look at and compare to tension charts.
 
The calculations and tables are fine. But this thread is interesting as in science we like the experiment to confirm the calculated theoretical values.
So I really hope that some brave soul will rig something up and give us some data to look at and compare to tension charts.

Sounds like a fun activity for a nerdy ukulele group or festival.

Participants bring fresh sets of different strings to spread the costs.
 
For what I am doing, I don’t care about the actual string tension. What I’m concerned about is being able to arrive at hopefully a “useable” comparison of two strings on the same instrument.

If one mfg sells a high tension string that is within that mfg’s own line. There is no quantifiable way to compare it to another mfg’s string; short of building a testing stand.


Aha. You can use string makers specs to estimate the variation in string tension before spending money (and perhaps mail order time to arrive)

My simple rule of thumb is to compare diameters for strings made of the same material - thicker means higher tension.

This works for me because after looking at pros and cons, I like unwound fluorocarbon aka pvdf and snappy tension.


The theoretical online string tension calculators have no company proprietary information of tue different strings to make an accurate comparison.

A feasible assumption is that the brands have the same density for materials of the same type because the raw pellets come from the same chemical factories.

Internet sources indicate that the fluoro string brands use the same raw pellets and equipment, and that almost all basic strings are extruded at a limited number of big fishing line factories.


My understanding is that almost all nylon strings use Nylon610 or Nylon612 filaments from a few factories, so comparing nylon strings by diameter should work for most brands


I have no info about density of brand specific blends like Nylgut, Super Nylgut, sugar, etc but we can compare diameters of strings made of the same stuff


I’m hoping this gives me another data point so using a high tension string that .001” thinner in diameter for a C string removes the thud but maintains the sound I’m looking to get.

General Method:
  • Choose an Option A, Option B, or Option C to winnow candidate sets to a practical number for testing
  • Buy and test a few sets at a time to zero in on sets you like
  • tilt the choice by easy availability, feel, durability, price etc

Option A: Use any of the free online string tension calculation apps (all based on the Marin Mersenne equations):
  • Enter your current specs for your favourite material, and fiddle with variables to get a density parameter for that material.
  • Use the density parameter, string length and the available brand diameter specs to calculate probable numeric tension.
  • Note: ?? Does the Mersenne equation lets us calculate and compare string tension between different materials if we can reverse calculate a density parameter for each material??
Option B:
  • start with current string diameters and decide if higher out or lower tension is needed
  • compare string diameter specs of available brands of the same material to guess comparable string tension
Option C:
  • Technical measurement of string tension of actual products
  • Use the initial results to guess string tension of incremental diameters
  • aka Empirical method
  • aka brute force method haha


Cheers


 
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@casualmusic, those are good suggestions, but I’m in a different situation. I’ve got rolls and rolls of Seaguar fluorocarbon.

I would like to find another mfg of equal quality to fill in some of the size gaps.

I enjoy the challenge of building a set for each of my ukuleles to try to maximize the sound/tone.

Sometimes it is an exercise in futility, but when I can get the mix just right it is so worth it.

John
 
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