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Headstock angle question?

Discussion in 'Tele Home Depot' started by old wrench, Jan 20, 2019.

  1. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    This discussion got me thinking, which can be a bad thing. I worry all the time about string break angles over the saddles of acoustic guitars and archtops and resonators - I'm pretty aware of this as I build and set up these styles of guitars. But frankly I had never given the nut end much thought. Long ago I built my first guitar pretty much based on what people had been doing for a few hundred years, seemed to work fine. My criteria at the nut were pretty simple - I didn't want the strings to pop out of the slots (and I really don't like deep slots), I didn't want the strings to bind when I tuned them, I wanted a fairly straight path from the nut to the tuner post, I wanted the guitar to fit into an available case - pretty simple requirements.

    I was somewhat influenced by the repairs that I make to instruments with broken heads. I also am pretty traditional - I like the heads of my guitars to look "right" for the style of guitar. I have to admit I'm not a big fan of Fender heads in general, but if I'm building a Fender style of guitar I'll probably put a slab head on it.

    From time to time there will be a discussion on some internet forum about the effects of nut break angle - the usual (unsubstantiated) claim will be for more or less "sustain" (the holy grail of electric guitars). I mostly blew these off - I'm an engineer and I either want to see the math or some sort of well designed experiment that attempts to "prove" whatever point the poster is trying to make. I'll add here that in the world of acoustic guitars there is some very interesting experiments trying to validate those phenomena that we think we hear.

    So, anyway, this got me thinking. What is the typical break over angle at the nut on different headstock designs. Out to the shop with an arm load of gutiar cases.

    What I did was very basic - I just measured the angle of the string from the nut to the tuner post as best I could (without going thru a whole lot of effort). I zeroed my little digital protractor and clamped a couple of blocks of wood across the arm so they would sit on the strings. I made an effort to fit it into the top of the slot and measure the angle as the string breaks towards the tuner. Something like this

    IMG_4931.JPG


    Anyway, here is what I got.

    Telecaster clone, two string tees, readings from low E to high E. 15.4, 8.6, 10.5, 10.5, 12.5, 12,5

    Les Paul clone - low E and D string. 14.0, 12.5

    Slot head 00 - low E and D string 24.0, 19.5

    Mmmmmmmmm......

    What is the optimum angle here? The tele is all over the place, but of course that is largely determined by where and how tall the tees are. The low E has lots of break angle because the tuner is close to the nut and the string wraps are fat so they go farther down the post. The 5th string has the least break, you can see that from the picture. The tees give the other pairs of strings the same angle, maybe they should be put in some other position to optimize these strings. Or not.

    The LP has pretty much what I would have predicted. The strings follow the 16 degree angle of the head, but the height of the tuner post lessens the angle a bit. The slot head is similar - still a 16 degree head angle but lots of break because the posts are down in the slots.

    (This brings up an interesting question - Rickenbacker 12 strings have a combination of slot and paddle head tuners, every other string. If one of them is better than the other, more sustain or whatever, why would a manufacture not just use the "best" one?).

    There is a lot of really good math out there for analyzing the forces at the bridge of a guitar - there are rotational components and components into the top and shear components - the same math would apply at the nut. But you know what, each of those guitars above sounds pretty darn good and the string work pretty darn good too. They tune fine, the strings don't pop out of the slots, I've got jigs for making 16 degree heads.

    I guess I don't see any reason to change.
     
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  2. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    double post - forum acting up
     
  3. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    My personal feeling is that you do the best job you can of laying out the string paths, ideally they don't interfere with each other, is relatively easy to change a string or restring the guitar, and the string doesn't bind in the nut slot when you are tuning. I try to make the nut so that the string exits straight towards the bridge, but the vibration is stopped at the edge of the nut (which opens a whole 'nuther discussion about stiffness and nut compensation and string physics and....). Where the string exits towards the tuner I ramp or angle the slot so its as straight as possible

    Sometimes you just do the best you can

    IMG_2015.JPG
     
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  4. old wrench

    old wrench Friend of Leo's

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    This "break-angle" controversy is exactly what I was trying to address in post #15. I was speaking of "break-angle" at the bridge, but from my perspective, it seems the same physical forces and effects are in play whether the "BA" (easier to abbreviate:)) is at the bridge or the nut.

    I've had the good fortune to play a lot of different "good quality" electric guitars, some with very different bridges and tailpieces and nuts and headstocks, and yet they all played and sounded good to my ears and hands.

    For electric guitars, anyhow, I'm thinking more and more that once the minimum force required to keep the string in contact (at tuning tension) with either the saddle or nut is met, "the job" is for all intents and purposes, done.
    Any force beyond that is over-kill, not necessarily a bad thing, but over-kill just the same.

    I'm not sure how that force would be quantified or expressed, but I will say it has to be a rather specific and quantifiable force, don't ya'all think? o_O

    It's always a real pleasure to exchange ideas with folks who are willing to think, rather than just react, or google an answer :)!



    Best Regards,
    Geo.
     
  5. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Geo, as I said above, I haven't paid any attention to the forces at the neck, but they would be exactly the same as those at the bridge. Here is a pretty good diagram of whats going on at the bridge

    upload_2019-1-23_16-13-54.png

    The static string applies a down component at the saddle, a shear component along the bridge to top interface and a rotational torque component at the end of the string. Depending on the exact geometry those forces can vary a lot. For example, on guitars with tailpieces (archtops, mandolins, violins, resonators), the break over angle phi is small so the rotational force F1 is also very small. Almost all of the strings tension is anchored at the tail piece. There is a significant downward component F3 which is what moves the top - the bridge literally moves up and down.

    The break over angle on typical archtops runs 12 to 16 degrees, amazingly close to what we are seeing at the heads of some of the guitars I measured. One of the basic setup rules with archops it to increase the break angle as much as possible within the limits of the top deflection.

    IMG_4548-3.jpg

    On guitars with bridge pins or a tie block (or for that matter, a string thru telecaster) the rotational torque is much larger and the bridge is rotated around its base axis (which runs into the paper at "a"). The area behind the bridge is pulled up, the area in front of it pushed down. When the string is plucked it is first pulled so it is longer, increasing the tension, then released. So along with some up and down movement there is significant rocking of the bridge - that's how a pinned bridge acoustic makes it's sound.

    TORQUE-LOAD-300x160.jpg

    I measured my LP clone with a top wrapped stop bar, it is over 20 degrees and would be more if I ran the strings straight from the stop bar to the bridge

    IMG_4930.JPG

    On an acoustic with a pinned bridge that angle can approach 40 degrees depending on the pin holes.

    So, what does all this mean at the nut? Well here are some general observations. We know the tension in the little piece of string going to the tuner is the same as in the playing length - if it wasn't it would move, right? The sharper the break over angle the more rotational torque will be applied at the nut (meaning it will be easier to break the head). However more downforce will also be applied, which in theory would make the nut want to vibrate. Now its pretty unlikely that will produce any real sound (remember that the vibrating bridge needs to drive the top to make sound at the other end) but it probably will absorb some string energy, which implies, at least, that it might reduce that holy grail, sustain. Or maybe the fact that its vibrating will feed energy back into the string, making it sustain longer. Pick your favorite.

    As you decrease the break over angle at some point the down force is no longer enough to hold the string in the slot - that must just suck the energy out of the string. We know it buzzes and makes all kinds of bad noise. So we put our little string tees on but really don't know how much angle is optimum. A big factor might be the difference in height of the nut off the neck plane compared to the saddles. Typical bridges will be anywhere from 1/2 to almost 1 inch off the top, the nut is typically 20 thousands or so over the f/b which is typically 1/4 inch above the top. That would seem to make the shear component at the tuner much higher and would reduce the down force compared to the bridge. Which might transfer more of the vibration into the mass of the head. Or not.

    Lastly, of course, all of this goes out the window the minute we fret a note - now you have a piece of string from your finger to the nut (at the same approximate tension as the vibrating length of string) but you have dampened all the vibration in that piece of string with your finger. The mere fact of putting your hand on the neck of the guitar has probably added significant dampening to the neck - again affecting the sustain. The break angle and rotational forces are still there but they don't affect the vibration of the string.

    That was kind of a stream of conscious thing. I'm sure its totally full of holes and people can have a field day poking them. My conclusion is that while there is a great deal of physics going on at the nut as long as we are within a range of parameters its going to work just fine.

    Now, what was the question again?
     
    Last edited: Jan 23, 2019
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  6. jvin248

    jvin248 Doctor of Teleocity

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    .

    Don't try this with your Gibson neck.

    [​IMG]

    I stopped buying Gibson guitars because I get headstock breakage anxiety and what's the use of having a guitar that needs to live in the case and only get opened to occasionally gawk at it? Will they ever switch to a scarf joint? I want a guitar I can play and not worry about. So I play Epiphones and Fenders.


    [​IMG]

    .
     
    Last edited: Jan 23, 2019
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  7. epizootics

    epizootics Tele-Meister

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    Yup - the more guitars I build, the more I realize there are 'minimum requirements' rather than 'best options' to many of the factors we have to take into account. Thanks for your long stream-of-consciousness post, some good food for thought in there!

    However, many my builds these days include a tremolo of sorts, which seems to complicate some of those 'minimal requirements'. For instance, the break angle at the bridge with a Jazzmaster-type trem, and how much string length there is between the bridge and the tremolo plate. With these, the construction verges on what would be considered problematic design options on hardtail guitars: the strings apply a downward force on the bridge that is barely sufficient to keep them in place, and a whole lot of vibration going on behind the bridge (what some call the 'trademark JM sound'). In such cases, one has to think more of the friction points than one would without a trem.

    I guess what I'm struggling to write here (twelve hours at work yesterday in the freezing cold fitting new windows and doors in somebody's house, with a bad cold and a busted back) is that I'm trying to find the 'minimum requirements' for such situations, and we're going off topic again here. :)
     
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  8. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I am not an expert on tremolos - I'll install or set one up if I have to but basically I don't like them. If the manufacturer recommends it (Kahlers, Floyds...) I always install a locking nut - that simply takes the nut out of the equation. If the trem action requires string movement over the saddles (Bigsby) then I like roller saddles. I'm particularly fond of Kahlers from the design standpoint - pricey but nice. It seems like the big bugaboo with every trem is getting them to return to tune, again, I just do the best I can.
     
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  9. Teleterr

    Teleterr Friend of Leo's

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    From my experience there is an angle minimum for sustain and harmonic content for both the bridge and nut string angles. It is NOT linear. After a theshold where it becomes good, changing the angle more increases sustain less and less . The RATE of change slows. W the Harmonics theres a sweet spot, depending on what you want, where the harmonics start becoming stronger. I d recommend a sharp bridge angle, then you can fine tune the nut angle w string trees if necessary, and then veneer the head if the prior tiny holes bug you. I had a Hondo? Lazar where the tone and sustain from the excellent , but misused, Schallar bridge/tuners was crappy. It was too shallow over the bridge. I sharpened the angle w a seperate bridge and it sounded much, much better.
    I d check the angle of guitars that sound good to you and copy that.
     
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  10. Donelson

    Donelson Tele-Afflicted

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    I believe this is incorrect. I have been looking into this a lot for 2 days. Gibson used 17 degree headstock angle from 1903 on. Norlin era is when the angle was reduced to 14 degrees. Roughly coinciding with when they were using volutes. Since 1983 or so, back to 17. I have four Gibsons, 1993 through 2016. All are the same, 17 degrees.
     
  11. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    It appears you are correct.


    http://www.guitarhq.com/gibson.html#specs



    • Pegheads
      • "Snakehead" peghead, narrows towards top: 1923-1934. Discontinued all models except L-5 by 1927. Discontinued L-5 1934.
      • Fiber peghead veneer replaces "Holly" wood veneer: 1970 to present. Also "Made in U.S.A." impressed in back of peghead or on decal.
      • Peghead angle is 17 degrees: 1904-1966.
      • Peghead angle is 14 degrees: 1966-1983 (approximately).
      • Peghead angle is 17 degrees: 1983-present.
      • "Volute" on back of peghead (most models): 1969 to 1981.
      • Thickness of peghead uniform: 1955-present. Prior to 1955 peghead narrows in thickness towards top.
     
    Last edited: Apr 5, 2019
  12. Vizcaster

    Vizcaster Poster Extraordinaire

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    When you measured the 00 slot head acoustic, did you have a chance to play a similar acoustic with a slot head and the same scale length? The slinkiness or compliance of the strings when fretted, the actual left-hand feel and playability, is much different with a slot-head acoustic than it is with a similar guitar with regular vertical-post tuners. I have no way to say if it affects tone or sustain but I do feel a difference trying to bend strings on the lower frets. For instance I can feel a difference comparing my Taylor 322ce with my Martin 000-28 (same scale length, same strings, one is slot-head and one is not).
     
  13. darren7

    darren7 Tele-Holic

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    Fender headstocks have no angle at all... the grain runs straight through. The break angle over the nut comes from positioning the tuning machines below the plane of the fretboard, and the use of string trees. It's a compromise solution that was mainly intended to make manufacturing cheaper and easier, with less material wasted.

    For me, 10° is the perfect break angle. Sufficient downward force over the nut, without introducing too much friction, and also less weakness due to short grain. Even better if done with a multi-laminate neck with a volute, or a scarf-jointed headstock.
     
  14. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I assume that was addressed to me, since I'm the only one with a double ought here. The answer is yes and no - most of the guitars I make are slot head but I also build a few paddle heads My criteria is pretty simple - if I'm building a funky guitar inspired by those wonderful old Depression era guitars and its 12 frets clear, its a slot head. If its 14 frets clear and inspired by more "modern" guitars (post 1930 LOL) then its probably a paddle head. If its an electric inspired by Gibson, then its a paddle head with the adjuster at the nut. If its supposed to look kind of like a Fender then its a slab head, probably with string tees.

    My guitars are all over the place on scale length, fretboard configuration, string gauges, yadda yadda - so it really isn't fair to say that I'm comparing two identical guitars - but I would probably agree that there is a difference in the feel of a slot head and a paddle head. I won't say I prefer one and so I'll keep building them for the mojo.

    Different sizes, different woods, different scale lengths - all slot heads

    [​IMG]
     
  15. otterhound

    otterhound Poster Extraordinaire

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  16. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Can you give me an example of a bridge design like this? It sounds pretty much like a standard acoustic bridge with some of the measurements changed. Pins are simply a convenient way to hold the strings to the bridge - you could certainly drill string sized holes and feed them up from the bottom with the balls pulled up against the bridge plate. People have put metal plates on the bottom of bridge plates when they get chewed up - however many folks think that adding a lot of mass to the bridge is probably a bad idea. And cutting down the thickness of the back of an acoustic bridge might change some of the angles in my diagram above, but it would still be working the same way.
     
  17. otterhound

    otterhound Poster Extraordinaire

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    First thing is to eliminate the pins . Throw them away because they will not be used .
    Second thing is to place a piece of material under the existing bridge plate that is drilled to allow the strings to pass through and retain the ball ends . The bridge plate remains untouched .
    Third thing to do is to reduce the height of where the strings exit the bridge and turn to the saddle .
    Do not consider what is not there .
    Only consider what is there and describe the effects that will be present from the string ends to after the strings pass by the saddle .
    I can tell you what I believe but I want to hear what you believe will be happening .
    After you share your thoughts with us , I will show you the prototype and explain .
    Honest discussion can take place afterwards .
    Please .
     
  18. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    OK, here are my thoughts. I assume this is an acoustic instrument, therefore its primary method of making sound is somehow moving the top. I'm also going to assume that it is more or less a standard acoustic configuration - lets say X braced with a bridge that looks pretty much like a Martin belly bridge I'm also going to assume that the string holes remain about the same distance from the break point of the saddle (a half inch or so, that there may or may not be some ramping as the string enters the hole and that the hole is more or less perpendicular to the top. In other words we are making those changes to a Martin style guitar.

    TORQUE-LOAD-300x160.jpg

    - Eliminating the pins is a wonderful idea, they are a PITA but a very convenient method of anchoring the strings. As you know, the pins don't really hold the strings in place - they simply hold them against the bridge plate. Either the pins or the bridge and bp are slotted to let the string pass thru to the top, I slot most of mine and have actually removed the pins with the strings under tension (its kind of scary, you expect the balls to come flying out and hit you in the eye). Also, as you know, there are many pinless bridge designs - they mostly seem to work fine (however the break angle might change with negates one of the assumptions above). Classical guitars (mostly) have their strings tied on, same argument.

    Bridge pins may have a minor contribution to the strength of the bridge to top joint but any good wood working glue should be much stronger in shear than the force on that joint.

    - Next, the reinforcement for the bridge plate I don't understand. The bp has two functions - it protects the soft spruce top from the force of the balls, and is a significant brace for the top. Bridge plates are usually made out of a fairly strong material - maple and rosewood (scraps from backs) are common. There are folks who argue about the mass of bridge plates - I'm a believer (I had an old D-18 "Kimsefied" with the big rosewood plate replaced by a small maple one - in my opinion that made a huge difference in the guitar). I assume your piece of something under the plate is to add reinforcement - if you feel you need it fine.

    There is a device called, I think, the plate-mate which is a piece of brass drilled to allow the strings (and pins) to pass thru to "repair" damaged bridge plates. It glues or otherwise affixes to the bottom of the bp - I assume yours is something like this. I personally would feel that this is counter productive.

    However, if your goal is to add mass to the bridge area (maybe to increase sustain) then the plate-mate or anything else would take you in that direction.

    - Reducing the height at the back of the bridge basically says you are making it less thick. That would remove mass and probably change the string break angle. Changing the break angle is one of those "magic" sort of setup things that people do with acoustic guitars (usually by slotting and ramping the string path as it exits the hole. I think that is a worthwhile thing to do and most of my bridges are ramped. I can't prove anything and its kind of like the first questions in this thread about angles at the head. One thing that does concern me is strength of the bridge - they do split thru the pin holes and of course its always the belly that pulls up first.

    - Next I'm assuming that total saddle height over the top remains the same - lets just say a half inch. That means that the driving force on the top doesn't change. If none of the angles in that little force diagram (here it is again) don't change and if the distance between a and c are the same, then I don't see where the tone or volume of the guitar will be any different.


    torquemodel.gif

    - I'll add one more comment, bridge to top glue joints shouldn't fail but they do. That is probably the most common "failure" I see (I don't consider broken heads or split tops "failures"). Every kind of bridge design - pinned, pinless, tied - all seem to fail. Floating bridges don't fail, but their forces are completely different. Glued on fixed bridges seem like one of the real weak links in the acoustic guitar design.

    So I'll end by saying you really have my attention - what'cha got?
     
  19. otterhound

    otterhound Poster Extraordinaire

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    I will start at the beginning . You based everything on other things instead of looking at this as is .
    A large part of the torque effect on an acoustic bridge stems from 2 places .
    In no particular order , they are the pins themselves and the point where the string turns from the pin .
    The bridge pins on a pinned bridge are anchored to the bridge .
    The string exerts upward pressure on the pin . which transmits that upward pressure on the bridge . That point is behind the saddle . This creates a tendency for a separation of the bridge from the top that is in torque . Even if the pressure on the pin at pitch is rearward , that creates a torque load at the back of the pin upward .
    The bridge must be thick enough where to pin is located to provide enough surface area for the pin to stay put via friction . Typically , at least on a Martin , this is approximately 3/8" in height
    Since there is equal tension along the entire length of the string from anchor point to anchor point , the distance that the string travels upward through the bridge is another fulcrum point that tends to torque towards the anchor point at the headstock . By lowering that height , the torque on that surface will lessen and if lowered enough , it will also create a load downward towards the top . This will have the effect of a pinch point that will tend to pinch the bridge and top together .
    The pins have mass . The plate under the bridge plate can replace that mass . The amount of mass in that plate can be almost infinitely be altered and placed . Not exactly an option with pins since they are all of uniform size and located only in their respective holes .
    I am going to test some of this with an electric build . I have done the pines bridge with an acoustic already and it works fine using Lexan as the plate material . Strong , tough and seemingly acoustically transparent , it is serving well . Best yet is that the plate can be removed and conventional pins used if so desired .
    Back to the electric build . I am going to construct a Tele with a half bridge that is not screwed down . I will provide locating points to prevent forward and sideways travel of the bridge that will not prevent the bridge from rolling towards the nut . Yes , I am using a string through body application in order to mimic the pinch point . I am curious to see if the bridge will stay in place . In order for the bridge to roll forward towards the nut , it will have to overcome the tension of the strings breaking over the bridge .
    Please forgive me if I lack the proper words to express my thoughts .
    The key is to see this as it is and not compare it to the conventional processes . Just because they work does not mean that this will not .
    Oh yeah , the picture .
    [​IMG]
    I almost forgot .
    You will need to look closely , but I assure you that there are no bridge pins
     
  20. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I'd love to see more and closer pictures, both of this guitar and the one you are building. I also need to meditate a bit on what you are saying - I'm so used to the current configuration that its a bit hard to picture this.
     
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