String tension project anyone?

[Gruuve]

So, I'm still doing some research into string tensions. So far, there appears to only be two mfg's who actually report string tension numbers: D'Addario and Thomastik-Infeld. The others don't publish the info. I've called two mfg's...DR says they don't have the info and even if they did they wouldn't give it out. OK...wow, must be some carefully protected trade secret, eh? Dean Markley doesn't have the info available, but has committed to trying to find it and calling me back with it. We'll see.

 

In the absence of string tension info, we can always use D'Addario's gauge/tension chart to estimate it. Since there's essentially only one way to make a string (albeit with some variations), estimating it using a known source will get you close.

 

However, since we have a formula (thanks to D'Addario) to calculate string tensions using the unit weight, scale length, and tuned note, it's possible to calculate string tension for any string. You just have to know how much one inch of the string in question weighs, then plug into the formula.

 

With that in mind, is there any interest in collecting unit weight information on various strings and calculating their tension? This could be done in one of two ways:

 

1) When you take off old strings, carefully cut a few 1" sections from each string (say 3), weigh those, and record the raw number or average them. The weight is in thousandths of a pound though, so a bathroom scale obviously won't work. That's the only drawback to this approach. UPDATE: Actually, it would probably work better to cut a 10" section, weight that, then divide by 10. That minimizes any error from cutting length variances.

 

2) I'm willing to buy a scale precise enough to do this. (In fact, this inexpensive one looks ideal...$13 and it measures down to 0.01 ounces, which is well into the thousandths of a pound. Digital scale at Harbor Freight Tools ). Folks could mail me a 12" piece of each old string they take off a bass, I'll cut it down to a 10" piece, weigh and divide by 10 (to eliminate length cutting variance), do the calcs and post 'em up. You'd have to label each string piece in detail though...the brand/model/item#, gauge, nickel or stainless, etc. The benefit here is that the measurements would be more consistent (and thus hopefully more accurate) since it's one person doing the cutting and measuring in exactly the same way.

 

I'm not sure the results would be all that much different from just estimating it based on D'Addario's tension info, but who knows for sure until we give it a try. I'd expect that 80% of the strings would be within a couple percent of the estimated numbers, and maybe 20% would be quite different from the estimated numbers.

 

Post and let me know what you think. If enough people are interested in participating AND would find the info valuable, this might be a worthwhile exercise. I'll be happy to actually do the work if enough folks are interested.

 

Now, there's a source of error in using old strings rather than new strings. Presumably, some of the string may have worn away, which would reduce the unit weight and tension. But, presumably same said string has accumulated some oxidation and probably your grease, sweat, and other genetic material , which would help balance out the difference. (If we do this, please try NOT to send me your DNA samples as well as string samples...I'm not in the FBI and I don't have any use for those. ) I'm not willing to buy one of every available string new just to cut a piece and weight it, and I doubt that you are either, so using old strings that we would throw away anyway seems like a reasonable compromise.

 

Dave

 

[Tom Capasso]

Dave, I don't want to stand in the way of personal discovery, but I've not found that string tension is a key decision point in my string purchase criteria. That said, I support your willingness to test and share.

 

I do wish I could see the look on your wife's face when you try to explain why you keep getting envelopes in the mail from all over the country (world?) with cut bits of bass strings....

 

Tom

[rdepelteau]

You don't cut a 1" piece of the string to measure it's weight, you weight the whole thing, and divide the weight by the length.

 

 

[Gruuve]

Dave, I don't want to stand in the way of personal discovery, but I've not found that string tension is a key decision point in my string purchase criteria. That said, I support your willingness to test and share.

 

Understood! I realize many folks probably aren't as nerdy as I am about things like this.

 

I do wish I could see the look on your wife's face when you try to explain why you keep getting envelopes in the mail from all over the country (world?) with cut bits of bass strings....

 

Tom

 

She's mostly used to my eccentricities, as I am of hers. Mostly, that is.

[Rocky McDougall]

Dave, one other factor you need to figure in. Old strings have streached and the inner wire has become smaller, so the weight per unit of old string may not tbe the same as a new string.

 

I also agree with Tom as to the value of this information.

 

You could cut the units to 1/10" and then multiply by 10.

 

Rocky

[TimR]

Here is an experiment I performed earlier.

 

http://phoenix.phys.clemson.edu/labs/224/standwave/1.jpg

http://phoenix.phys.clemson.edu/labs/224/standwave/7.jpg

 

Make the distance from the clamp to the pulley 34". Add lead shot to the bucket until the string is in tune.

Weigh the bucket.

 

Do this in your shed. Make sure that there are newspapers over the windows and keep a pan of boiling water near the door so that the steam wafts out. Hit things with hammers every now and again and swear loudly.

[Gruuve]

You don't cut a 1" piece of the string to measure it's weight, you weight the whole thing, and divide the weight by the length.

 

 

Actually, no you wouldn't weigh the whole thing...you'd weigh only the vibrating length, so you'd need to cut it to a 34" section that represents the vibrating length, then divide the weight by 34. (Or cut 35, weigh, and divide by 35.) Unit Weight is pounds per linear inch...check the formula. 10" seems like an easier length to mail and work with and it's long enough to minimize cutting error...that's why I chose it.

 

Tim, that fixture is hilarious! I love it...

 

Rocky...simple minds, simple pleasures?

 

Dave

 

[alexclaber]

This is the kind of thing that bothers me too! However I don't think your suggested method will produce sufficiently accurate results, Dave. The kind of rig that Tim found photos of is more likely to produce the precision we need.

 

Even if you get mass per unit length for every string on the market, that will only get you the static tension for a string. As soon as you pluck the string the system becomes dynamic and very complex and furthermore there is quite a difference between tension and feel, as feel takes into account the stiffness of an unavoidably imperfect string.

 

D'Addario's tension charts will probably give you as accurate a picture of tension as any experiments will. To find out tension for a string find the D'Addario model that is closest in construction - i.e. outer wrap shape, gauge, taper, and material. Based on this I ordered a custom balanced gauge set for my forthcoming 5-string. Once it's built I'll let you know how balanced 40-55-75-100-130 nickel roundwounds feel!

 

Alex

[TimR]

Yes joking aside, that appartus is common in physics labs in 'high schools' in the UK. It's used for demonstating exactly what you are interested in. You could make up something very similar using an old string through bass. Just leave the string loose and attach whatever you are going to use for your bucket to the ball end of the string underneath the bass. You might be able to find another way of suspending the weight using a 'normal' bass bridge. You could then use an electonic tuner to get accurate tuning.

 

A rig like that was present at my audition for the first band I was in. The physics teacher was doing a lesson on standing waves in strings and asked us all to bring in our stringed instruments. We plugged guitars into oscilloscopes and looked at string vibrations under strobe lights. One guy liked the same type of music that I did and played guitar. The rest as we say is history.

[rdepelteau]

How accurate do you need it to be?

 

If you're building a spring loaded bridge, then 20% accuracy is plenty, but if you're building a neck, then you should work with a factor of 100% so using the specs of Thomastick strings should be accurate enough.

 

What are you trying to do?

 

[Gruuve]

...However I don't think your suggested method will produce sufficiently accurate results, Dave. Alex

 

Ya know, you're probably right about this. The unit weight difference is probably so small across different strings of the same gauge, this might very well be an exercise in futility. Next time I change strings I may just cut some pieces and compare just see if there's a different in unit weight substantial enough to even justify not just using D'Addario's tension charts to estimate it.

 

If I do uncover any difference substantial enough to bother with this project, I'll repost. There ya go.

 

Dave

 

[Bruiser]

I've been toying with the idea of building a device to measure string tension on the bass, where it really matters. It would be based on a device used by people who build or repair bicycle wheels, called a tensiometer, to measure the tension in spokes.

 

I don't care that much about the tension in strings, per se, but I think it would be interesting to test some of the ideas that people propose, like the famous circuit board stand-off fix that Gary Willis mentions in his book.

 

I think I could put together such a device with pieces and parts laying around my lab at work (on my own time, of course). Building devices to measure things is more or less what I do for a living.

 

Of course, I've been toying with this idea for about five years, and I haven't felt ambitious enough to do it yet. . .

 

Ed

 

[Rocky McDougall]

Dave, I believe the only part of the string that really has a major effect on the tension is the center wire of the string. I don't think the outer winding has a lot of effect on the tension. The diameter of the center wire of a string may vary considerably from differnt manufacturers eventhough the outer deminsion is the same. So there maybe strings of the exact same weight that may have different tension because of the difference of the center wire. What'ca think?

Rocky

[TimR]

Fair point, but I think that it is the mass of the system. EG the outer coils are part of the system, while they are not tecnically under any tension, they are adding to the mass of the vibrating part.

 

So yes the center string holds the tension, but the whole mass needs to be considered.

[Gruuve]

Yup, agreed. The outer windings don't hold any tension, but they do add to the mass. Think back to physics experiments in school...when you add weight to a reciprocating spring system, it slows the reciprocation rate. Same is true of strings, and the measurement of mass is the unit weight in pounds per linear inch. If you add weight (larger gauge) this slows the vibration rate (which would require more tension to bring the vibration rate back to the right note), removing weight (smaller gauge) increases the vibration rate, which would require lessening tension to get back to the right note.

 

That said, I think differences in the core wire gauge with strings of the same overall gauge will show up as stiffness. Stiffer would be perceived as greater tension, more flexible would be perceived as lower tension. So, a 0.100 gauge string with a thicker core wire and thinner windings would be stiffer, the same gauge string with thinner core wire and thicker windings would be more flexible. Also whether the core wire is hexagonal or round might make a difference in stiffness. According to DR, round is more flexible and hex is stiffer. However, since DR does "compression winding" (they wind it larger than the intended gauge then smash it down to the target gauge), they probably use a slightly thicker hex core wire versus round core wire, which would put the hex core wire strings being a little stiffer...that would be my thoughts. I don't know right off of a good way to measure stiffness though.

 

Dave

 

[Rocky McDougall]

Do any of the string manufacturers give the specs of the inner and outer wire gauge? I imagine this is not openly shared; however, any interested person could disassemble and measure. Could four strings of the same inner wire diameter have different outer windings and still be tuned to different pitch or is it important to have different core sizes?

Rocky

[Gruuve]

Great question Rock! I don't think any mfg's give those gauge numbers. And I believe the answer is yes, you could put different gauge windings around the same core gauge and end up with strings better suited tension-wise to different pitches. Again, it all comes down to unit weight and thus what frequency the string vibrates at under a certain tension. Raising the tension makes it vibrate faster, adding mass makes it vibrate slower. Anything that adds mass (whether it's larger gauge windings, larger gauge core wire, or a different alloy that's heavier) is going to raise it's tension when tuned to a specific frequency. Based on the physics around spring systems (what this actually is), that will always be the case.

 

The reality is that wire sizes (both wire used as the core and wire used as the windings) is only available in a descrete set of sizes. I'm sure some of the string mfg's could get odd-ball sizes, but it would cost them more and you can be sure it would show up in the product price. In fact, I think Thomastik-Infeld uses some odd-ball wire sizes, and that's likely why a 5-string set of TI whatevers costs $65 rather than $35.

 

Dave

 

[Rocky McDougall]

As a side thought, I wonder who is the largest maker of the wire. I would like to see their catalogue of the different wires available. I doubt that many of the string manufacturers make their own wire. I may Google that and see what I can find.

 

Rocky

[Tenstrum]

Wish I could help, but the only thing I know about string tension is that when a string breaks from over tightening and hits you in the face, it tends to create a fair bit of tension...

[Gruuve]

Hey Rock...I seriously doubt any of the string mfg's make their own wire. I'd imagine every single one of them buys it from a supplier, then makes the strings from the wire. I'd say that making strings from wire is likely MUCH easier than making wire out of raw metal.

 

Just as a side note (or joke)..."DR, the hand-made string!". Yeah right! I can see a bunch of guys sitting there winding strings by hand..."Hey bubba, hand me them pliers...". Give me a break! It may be "hand-wound" but I think we can safely assume that some machines (probably automated ones) are used in the mfg process.

 

Dave

 

[Rocky McDougall]

The machines do have On & Off switches that must be started by hand, or, one finger.

In all honesty, I would rather have a string made by a highly accurate CNC winder than "Bubba" winding something together.

Rocky

[open strings]

http://www.daddario.com/Resources/JDCDAD/Videos/StringTension.pdf

 

you may have already seen this, but here it is anyway. It was written for guitar strings, but I assume the tension concepts apply to bass as well.