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  Tensil Strenght Test for Strings????

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Author Topic:   Tensil Strenght Test for Strings????
Ed Naylor

From: portsmouth.ohio usa

posted 27 September 2004 08:47 AM     profile     
The Auto industry test Autos for Rollover,Side Collision etc.-Has anyone done a 'Strenght" test on strings to rate the different Brands and Gauges????What effect would Guitar "Brand",Changer parts,Scale have on such a test.?Hopefully some Mechanical Engineer who knows Steels can help answer this question. Ed Naylor Steel Guitar Works.
Ray Minich

From: Limestone, New York, USA

posted 27 September 2004 09:09 AM     profile     
Ed, there is one stupendous string metallurgy/strength dissertation that appeared here in the forum the past year. It was really quite detailed. I'm sure it's in the archives. I'll post the link if I can find it.

I've found the my single most critical "string breakage" issue to be the condition the changer finger. Needs to be nice & clean and smooth and polished where the wire goes around the corner. Also, installing strings at 40 degrees F is a waste of time. (Garage needs to be heated in the winter)

[This message was edited by Ray Minich on 27 September 2004 at 09:14 AM.]

ed packard

From: Show Low AZ

posted 27 September 2004 09:14 AM     profile     
ED; Boy, does that open up a can of worms! I use a tensiometer for my tests that pulls on the nut end of the string(s). I have used it to measure tension vs stretch and pitch. Pushed to the extreme, it will show where different types and makers of strings products will break re tension, bend, twist, clamping, etc.. Needs lots of work and lots of strings for a meaningful statistical sample. One problem is not the string itself, but the change vs. tension in the ball/wind area.

A poor man's tensiometer is available at Wal-mart's fishing tackle dept = a digital fish scale up to 50 lbs. It is also good for measuring the force needed to activate levers/pedals.

Ray Montee

From: Portland, OR, USA

posted 27 September 2004 10:26 AM     profile     
HOW MANY string manufacturers are there, today?

Aren't we really just buying different colored wrappers with pretty much the same product inside?

This is what I was told a few years back and have really been upset every since. At this point, I have no idea of what I'm purchasing when I ask for a Gibson, Black Diamon or whatever.

chas smith

From: Encino, CA, USA

posted 27 September 2004 02:22 PM     profile     
I'd like to read that thread, mentioned above.

Because I don't know the alloy and the tensile, if I guessed, oil-quenched, high-carbon, it's 220 kips. So, the .011 string has an area of pi r^2 = .000095, and that multiplied by 220,000 = 20.907# so 21# of pull on the .011 snaps it, unless I'm mistaken, which wouldn't be the first time....

ed packard

From: Show Low AZ

posted 27 September 2004 05:06 PM     profile     
Chas; Just for the fun of it I tensioned my 0.110 SIT string to the breaking point. I can do this on my instrument because of the combination Changer/tuner arrangement. The angle across the finger is about 10 degrees if you want to apply the cosine correction to the break measurment.

The breaking point is more than 33# pull uncorrected for angle. The string did not break, the ball winding came undone.

One confusion re string material might be that the 0.011" (small diameter/cross ection) is material is largely surface, the properties of which are a function of the drawing process and perhaps not representative of the base material characteristics. A small increase in string diameter makes a big difference in the cross sectional area.

Marks Handbook, seventh edition, 5-5, gives Tensile Strength (KPSI) gives SAE 1300 annealed and drawn at 400F as 240; SAE 4340 annealed and drawn at 400f as 290. These are the highest listed steels in the list.

It would seem that the QA departments of the string makers should monitor tensile strength by batch at least; I have not been able to get them to provide any info on this. I can't even get mass data from them.

Gene Fields has some good words of info on strings in a paper on his GFI site.

Bill Bosler

From: Schwenksville, Pennsylvania, USA

posted 27 September 2004 06:30 PM     profile     
The laws of string physics dictate that strings will fail when:
(A)You're in the middle of a solo.
(B)After the first three notes of a song you kick off.
(C)When you're quickly trying to start the next set and you sit down at your steel and push the pedals.

Ed Naylor

From: portsmouth.ohio usa

posted 28 September 2004 05:49 AM     profile     
The Steel Guitarist Prayer that I wrote years ago-the last line-And Lord may I ask as my final plea, That I don't break string #3. ED
Rick Aiello

From: Berryville, VA USA

posted 28 September 2004 06:59 AM     profile     
Here is a nice Breaking Load Chart from a Music Wire supplier.

Here is a pretty cool Tension Calculator...


ed packard

From: Show Low AZ

posted 28 September 2004 07:51 AM     profile     
Rick, ..thanks for the sources, particularly the first one.
Ray Minich

From: Limestone, New York, USA

posted 28 September 2004 09:12 AM     profile     
Ed (Packard), it's your thread of 24 Feb 2004 titled "Strings, Gauges, Mechanics" that I was referring to. Lot's of good stuff there.

Hows about Kevlar strings? Not too tinny & boy can you pull on 'em

[This message was edited by Ray Minich on 28 September 2004 at 09:15 AM.]

Jim Palenscar

From: Oceanside, Calif, USA

posted 28 September 2004 10:31 AM     profile     
Our own Terry Downs has an absolutely wonderful technical web site that gets into lots of this stuff- for example string gauge calculations .
Joe Henry

From: Ebersberg, Germany

posted 28 September 2004 11:57 AM     profile     
I am not an expert by any means, but I know for a fact from my own experience that even strings of the same brand, same gauge obviously, will not always last for the same amount of time. A high G# string will sometimes snap after three days, another one of the same brand might last two weeks or more, with the playing time each day being more or less the same. I donīt think experiments like that will prove something unless you test at least a hundred strings or more of the same gauge, same brand.
I have found brands that sound better and give a better playing feel than others, but havenīt discovered one yet that makes strings that are really consistent when it comes to durability. Maybe itīs something physically impossible, or at least at present. Anyway, until that will be achieved (and guaranteed), Iīll always put on a fresh G# string before each gig.

Regards, JH

[This message was edited by Joe Henry on 28 September 2004 at 11:58 AM.]

Ray Minich

From: Limestone, New York, USA

posted 29 September 2004 06:22 PM     profile     
Does anyone know if strings are made by wire drawing (pulling the wire thru a sequence of increasingly smaller die holes until final diameter reached) or are they squeezed & rolled into shape.

I would suspect that wire drawing could put microscopic fissures on/in the surface that would limit the vibration cycles a wire could oscillate thru before ultimate breakage (i.e. catastrophic failure due to crack propogation).

When you come to think of it, a guitar string is a mechanical wonder. Thin, strong, and pulled on like he!!. Then asked to stand up to millions of vibration cycles.

Somebody correct me if my math is wrong, I've tried three different calculators (even an RPN job) and, for a 0.014" dia string with a 20 pound pull I come up with a tensile stress of 130 ksi. That's quite strong. Looking at the Mount Joy website I see the tensile strength for .014 wire is 369,000 to 408,000 psi. Holy smokes!!! Yer typical I-Beam material begins to stretch pretty good at about 30-40,000 psi.

Ultimately it's the connections. Usually in a mechanical structure it's not the member that fails, it's where it's attached that fails first (stress concentrations, etc.).

Here's a copy of the top of Mount Joy's chart.

Diameter Tensile Break
(inches) Range (PSI) Strength/Lbs..

.004 439-485.000 5.5-6.1
.005 426-471.000 8.4-9.2
.006 415-459.000 11.7-13.0
.007 407-449.000 15.7-17.3
.008 399-441.000 20.1-22.2
.009 393-434.000 25.0-27.6
.010 387-428.000 30.4-33.6
.011 382-422.000 36.3-40.1
.012 377-417.000 42.6-47.2
.013 373-412.000 49.5-54.7
.014 369-408.000 57-63

Interesting observation that as the diameter goes smaller, the tensile strength increases yet the breaking strength gets smaller. This must mean that at one molecule dia. the wire has infinite tensile strength and zero breaking strength.

[This message was edited by Ray Minich on 30 September 2004 at 07:36 AM.]

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