Last night i was alone in my work room / studio minding my own business when i was suddenly startled by a very loud "twaaannngggg..."  that really made me jump...first thing i thought was the old poltergeist was up to its old tricks again (they do exist, you know...) and wondered what else i was going  to hear that night....

 

This morning i found the culprit - my early build "The Captain" had its strings all wrapped around the neck in a most bizarre  fashion, and i realised the brass hinge they were anchored to at the tail had snapped through metal fatigue, this "antique" hinge i used only on this 4 string build, another on a 3 string build, i wondered what would have happened if i'd been playing the thing and all four strings had recoiled in my face - doesn't bear thinking about, though brass is soft and i guess can only take a certain amount of strain after a few months!  I guess the loud twang noise was the strings, still connected to the remains of the hinge, hitting another guitar, though sounded really spooky ...

 

Others may have years of use with brass butterfly hinges but i will not be using them again in future... (-;

 

.4 String Captain

Brass butterfly hinge taking the strain....until !

 

.

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The discoloration/marks you point out are caused by the very stresses John Maw describes above. Simply put its the beginning of the process of what would happen if you clamped the metal in a vise and folded it 90 degrees and straightened it and did it again. Some metals are more Malleable, and will tolerate it longer, but all will begin to work harden and lead to eventual failure.

Brass alloys have a very low tolerance for this.

It's enough to make someone come unhinged.

Dan. Did you have a particular someone in mind?

I think that Oily made a very interesting point. In his calculations he concluded that anything much less than a fire door hinge might be unreliable. Now we know that there are plenty of people making plenty of instruments using much lesser hinges and not losing eyes or being injured as a result. In fact a fire door hinge is designed to cope with more than just it's weight. It has to cope with constant use, knocks, people leaning on the handles etc. In short, it is intentionally over-engineered. But we should still be careful.

The hinge pictured above is not even a door hinge. It is a cabinet hinge intended for lightweight cupboard doors or largish boxes. In that situation it will probably outlast us all. It is fun making these things but with the wrong choice of components these guitars can go from instrument to catapult in a very short space of time. Out of interest, did you know that a concert size grand piano can pull as much as 20 tons in string tension. As someone said, "Be afraid. Be very afraid".

John,

So who is going to build the first CB baby grand? I'm already afraid...though I do wonder how many boxes you'd have to glue together...hmmmm.

Anyway, as usual this got me to reminding myself that I break individual strings all the time on my commercial gits, because of my heavy right hand attack. Once, very early on, I managed to snap the bridge off a cheap acoustic that wasn't mine, which indeed led the lender to become unhinged (glue failure). Point is, just playing can induce metal fatigue in a part not designed for the load, or the side stresses induced from picking / strumming. I've worn through two adjustable steel saddles on my Strat before switching them to Graph Techs. I also had to learn to modify my playing technique quite a bit, going from acoustic to electric.

Solved that problem by putting 12s on it. Now nobody wants to play it except me, and I get a much throatier tone.

But back to hinges...

i studied the broken piece and the ring part of the hinge is curled round, the whole hinge appears to be pressed not welded or soldered, the stress marks seem to be from the original pressing process.

Mark said:

Steve, I've been looking again at the pic of the broken off piece of that hinge and something is bugging me. There's some curious discolouration and surface texture around the areas where the cylindrical part joints the flat bit. I tried enlarging with Photoshop to show what I mean...
Looks almost as if that half of the hinge was welded or soldered together. Is there any chance the halves of the hinge might have been made from separate bits joined in that way or is it definitely one of the common type where each half of the hinge is just all one piece of metal and the cylindrical bits are made by just bending tabs over.

 

Slowpaw Steve T said:

Found the other piece of the hinge!   Comments appreciated folks, indeed a clear case of hinge misuse....amazing how much pulling power those slinkies have!!

 

Who said anything about a baby grand. Nothing less than a 9' monster I think. But that's why they put an enormous cast iron frame in the things. If anyone thinks they are building one out of cigar boxes then I am standing well back. Need more than a truss rod.

Oily "Strat-O'-Nine-Tales" Fool said:

John,

So who is going to build the first CB baby grand? I'm already afraid...though I do wonder how many boxes you'd have to glue together...hmmmm.
Whoever does it will need a truss of some kind ;-)



Roadkill a.k.a. John Maw said:

Who said anything about a baby grand. Nothing less than a 9' monster I think. But that's why they put an enormous cast iron frame in the things. If anyone thinks they are building one out of cigar boxes then I am standing well back. Need more than a truss rod.

Oily "Strat-O'-Nine-Tales" Fool said:

John,

So who is going to build the first CB baby grand? I'm already afraid...though I do wonder how many boxes you'd have to glue together...hmmmm.

shit fails ocasionally but for reasons you already know

Heres my latest guitar..using a cast brass bar-flap hinge. I very rarely use hinges as tailpieces, and these are the only ones I deem suitable for a decent instrument. You have to get a good break angle over the bridge to hold the strings in the bridge notches, as the strings 'fan out' due to the narrow hole spacings. It's a really heavy casting, and plenty strong enough for the job.

...now that's what i call a hinge! looks strong enough for the job, might consider changing the tailstock hinge on EKO for one of these, though anyway enough about hinges...

 

...WHO THE HELL PUT ALL THOSE BONY M TRACKS ON THE FRONT PAGE...?? GRRRR!!!! (-;

 

Hey, maybe someone could start building CBG hinges that practically never wear out or break:

 

StoneHinges

 

>:-E

nice to know I am not the only person who can make an exploding guitar :)

 

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