Ken Parker Archtoppery - Riff 023 - A Test Fixture to Help Explore Guitar Design

[@tommymaloney4167]

VJ just passed this video along to me and I’m so glad to see this test fixture is still in use! I designed and built it (atleast the first version of it, though it didn’t change that drastically) during my Masters program in the middle of Covid in my basement shop. It’s really cool to see the changes and upgrades you have made to the system for your own needs! I really like the change to the single screw system with the reinforced head. I didn’t do that in fear of the strength of the 3D printed materials I was working with at the time. I do admit that it was super difficult to keep even and stop the whole pice from rotating and binding in the channels. Also love to see the added ease of use with thumb screws and other pieces here and there! If there are any questions I’d be happy to answer any too!

[@pedroleal7118]

Thank you Ken, and the 'Lab Rats' for your efforts! We all can benefit from your hard work ! I totally agree, that humans are sensitive to incredible small variations, that translate into 'feel' but are hard to express! Be it string tension, string gauge , etc, etc (micro variations) ...! Please, keep up the good work ! ps the Luthier world is so much set into 'tradition' that sometimes it's hard to make them accept small experiments, which always translate in huge amount of work, out of their usual methods. I ended up designing my own original model, but it was such a struggle to make my friend Luthier accept it ! At the end, he ended up using some of the different solutions I proposed. I've been searching for a Parker (solid body) for a while now, but they are hard to come by, here in Europe, or, at prohibitive prices, even second hand, and you never know whet you'll get. any advice on what to look for? A happy Christmas and a Great New year to everyone at Parker guitars! Take care and thank you for sharing !

[@KDP61353]

I sent my Parker to VJ to have the electronics fixed. No easy task, but one of his associates did a fantastic job replacing the film wiring.

[@jeffkowalczyk]

This area of inquiry is fascinating and terrific basic science yielding evidence luthiers can build upon. I would be interested to know the effects of reverse headstock peg placement after-length on string tension. I think this could be done on the existing rig by changing the string order.

[@normbarrows2]

Supposedly, tension is constant along a string, regardless of break angle, string trees, etc, and is solely a function of gauge, tuning pitch, and scale length, or just gauge and pitch for a guitar of a given scale length. As I recall, a set of Ernie ball 8's on a Fender scale length is about 76-78 lbs of tension (according to Stringjoy's calculator) - and that's for a forward or reverse headstock (I've owned both in the past). After-length increases the amount of string available for elastic deformation, thereby reducing the effort required to deflect (fret or bend) the string. A reverse headstock has greater after-length on the bass side (as opposed to treble on a non-reverse), so bass bends should be somewhat easier and treble bends somewhat stiffer compared to a non-reverse headstock. Never noticed much of a difference myself. Like many thing in guitar, there's what makes a theoretical difference, and then there's what makes a _detectable_ difference.

[@skookum-rjb]

Interesting experiment, and I always love your constant efforts at understanding and improving guitars. I believe other comments below echo my thoughts. This headstock angle is all about the force down at the nut and how much that reduces the strings propensity to slide over the nut. If we start with the notion that if the string were totally fixed at the bridge and the nut, then the tension required to displace the string is dictated by the 1. distance of displacement, 2. string material of construction, ie youngs modulus (stress vs strain in the elastic regime of the material) and 3. the geometry of the string... diameter, windings etc. 4. String tension or pitch. With all those items fixed a longer scale length will reduce the force required to move the string. Essentially you are measuring the effect of a longer scale length by virtue of the string sliding over the nut. I would think that minimizing the break angle at the headstock will give you a reduced string fretting pressure. As an instrument maker, the limiting factor is buzz at the nut. Set the headstock break angle at the minimum required to eliminate open string fret buzz. If you never play open strings, don't worry about it. ;-)

[@DonaldMerand]

This is incredible, it's so amazing that you're doing this work and then sharing it! I was wondering also about the effect of the resonant frequencies of the after-nut and after-bridge areas on perceived sound - this fixture would also be amazing for testing that.

[@VegasCyclingFreak]

Interesting test fixture!

[@gpurkeljc]

My father passed away today. He liked watching these videos with me.

[@TyphonKrazilec]

Thabnks for this episode and Merry Christmas!

[@MDofTerryology]

Hearing about constantly needing to tune to pitch made me think of the robo tuners that Gibson used for a minute. This might be their calling, I don’t think many people liked them on their instruments 😂 Thanks for the insightful content as always!

[@jvin248]

Good fixture and testing ideas. I like how you can simulate Lutes! Some future investigations you can pursue with this aparatus: add the ability to simulate 3+3 headstocks (Gibson), reverse "Hendrix" 6-in-line (which just needs swapping string sizes by position), Scale Length changes (Gibson, PRS, Fender, Mandolin) and tuning stability. High Gibson headstock angles results in poor D-g tuning stability, many famous Les Paul players actually recorded in the studio with Telecasters because Teles keep great tuning stability. You should also measure "Sustain" of notes by string vs excess length beyond nut and saddles (Gibson D-g is poor vs E-e; Fender b-e is poor vs E-D; but that's reversed on Hendrix Style Strats, an important feature since most Metal players benefit from reversed Strat-style headstocks). You will find that Mandolins are very "plinky" due to having half their string length distributed beyond the nut and saddles vs headless and wrap-tail style electric guitars. The reason Gibson headstocks break so easily is because they based the LP/SG headstock on their main business of Mandolins, not sufficiently anticipating the increased tension on the longer scale length guitars. Put a load cell on the headstock adjustment arm to get an idea of the forward bending moment on the headstock for various headstock angles. Might even be interesting to compare headstock angle vs some sort of "Tone" measurement, using an electric guitar pickup and amp by string for different headstocks. I expect many guitar myths can be dispelled with this testing machine.

[@GitFiddler0123]

Wonderful, thank you for sharing this video!

[@kenparkerarchtoppery9440]

I'm so glad you're enjoying it!

[@BBGuitars]

This is an amazing test setup. What Im really interested in is how what you called the "after length" has an impact if any on actual tension required of the string itself when tuned to pitch...

[@andrewsguitars]

Thanks Ken! I have been following Archtoppery as a fan and a luthier. I fully understand you are going after the perceived as an easier feel, and that the string length from nut to saddle will be a measurable tension based on string makeup and pitch. So in my perception, I was at the notion that it was the added stretch of the string past the nut and/or saddle that contributed to the actual string performance, which would rely on friction at the contact points as much as anything. To use your example, the friction if the string over the delrin nut is considerably greater at 80 degrees than at 4 degrees. I would like to see this experiment performed using roller bearings to control for friction in the experiment. Another thing that you touched on that I would like to see is bending the string up a semi-tone or full tone and really engage the after string length. It might need a deflection distance to measure alongside the pressure. I have great respect and admiration for you as a luthier and a positive contributor to human achievement. Kudos to the Lab Rats as well!

[@alessandroferro5308]

Really interesting!

[@bluearchguitars]

Great project!

[@kenparkerarchtoppery9440]

Thanks! We'll be doing a follow - up, as there were so many great comments and questions!

[@Imposibilitron]

I saw an experiment on Devons Mullen's Instagram that the extra length after the bridge significantly reduces the amplitude of the string vibration. He used a much simpler rig: a board with two bass strings and two mono bridges, one string has a 9 inch "after-length". The hammer hits both strings at the same time and the string with the extra length vibrates with a much smaller amplitude.

[@normbarrows2]

Got a link ?

[@OpenWoodShop]

I immediately thought about lute headstocks. I'm glad you were too. I didn't expect much difference from that extreme headstock angle, but what I was wondering was if it was necessary because of the fact that they were using sheep gut strings and therefore needed a more extreme break angle. Still wondering. Hopefully you'll get some sheep before the machine comes back. :)

[@ebcline]

Couple thoughts about further testing perceived string stiffness. 1. With the straight string pull across the nut on a fly headstock (as opposed to angled pulls on the vast majority of instruments), and particularly with a vertical string displacement which reduces the break angle over the nut during the test and keeps the string in line with the nut slots, the longitudinal stiffness will be determined by the entire length of the string from the tuner to the saddle. Additionally, the vertical displacement is the opposite vector of fretting a string and 90 degrees off from bending a string, both motions that would change the relationship of the string to the nut. These things could explain the minimal effect of changing the break angle. Testing the stiffness by pushing down as in fretting or pulling across as in note bending may yield a different result. 2. It would be interesting to perform the tests again with different headstock/tuning peg arrangements. With string pulls that angle laterally away from the nut slots instead of straight like the fly headstock, the increased friction at the nut may be enough to reduce the effective string length to be between the nut and saddle. The reduced string length should increase the tension required for string displacement. However, just as with the straight string pull, because the effective string length is the primary factor, increasing the break angle at the nut will likely have only minor effect. Once the friction threshold to shorten the string is achieved, the break angle will do little to change the tension between the nut and saddle.

[@kenparkerarchtoppery9440]

All of this seems spot on to me. We'll be filming anotther little piece of commentary about this, kind of as a chaser, because of all thie interest and many comments and suggesstions received. I completely agree that the angles and afterlengths are a relattively minor part of the whole tension equation, but once we know what direction to go, well, at least I'll be happy to take advantage of it in service of unloading the player's hand. Let's hope that Sam and I have improved the Apollo device enough, and all of you enthusiasts have expressed enough interest so that the Worsester Polytechnic Undergrads/Grads want to join the Rats Project and spend some more time with this test rig. As I understand it, BTW, "Lab RATs" stands for Researchers and Tecnnologists at WPI, a guitar-studies related ongoing series of projects started by Music Professor VJ Manzo. vjmedia.wpi.edu/Lab_RATs VJ also created and maintains this site for lovers of Parker Fly guitars... flyclone.com/

[@SebastianBogensperger]

Lovely :D

[@kenparkerarchtoppery9440]

Thank you! Cheers!

[@vw9659]

The fact that the string bending device bends to a fixed string displacement means that you are presumably not actually testing to a consistent bent-string pitch under each condition. You would need an adjustable bending device, and bend the string until the same pitch (string tension) is reached for each headstock angle and post-nut string length. Which will show that the string needs to be bent further when effective string stiffness is lower (with less headstock angle and longer post-nut string length). Then you could measure the "finger" force at that consistent pitch on your scale (the result of the string tension and string angle).

[@Cshanghai]

The other factor to consider is change in pitch when 'bending'. Does an equal change in pitch in two conditions (greater headstock angle or longer after length) correlate to equal force exerted or equal displacement of the string? From a player's perspective "do I need to push harder when I bend with a greater headstock angle / shorter after length"? I'm sure you're already investigating that and I would love to see the results. What a brilliant way to quantify something that players have intuitively felt (and disagreed on for lack of objective data) for a long time.

[@ActuallySettle]

Looks like you're ready to start making a pedal steel. I'd love to have one with the low E tuned to the same 82hz as a guitar. Amazing fixture, love to see the data.

[@docdoc]

A pedal steel is too complicated for Ken Parker

[@KLG002277]

Would adding a spectrum analyzer (via some pickups, magnetic or piezo) add another great dimension to the results by giving you feedback on the amplitude changes to the harmonics? There are some great digital analyzers that will display multiple lines, in different colors, to better see the changes. BTW, really enjoyed this and so many more of your videos. Thank you for sharing your brilliant ideas!!

[@jonahguitarguy]

Very good testing device and good info. Like you I'm surprised that there wasn't a greater difference in tension from 82-7 degrees. If the string were only moved the 4/64" it takes to reach the fret I think the number would be even less. I know a lot of builders and players and Gibson would argue the downward string tension at the nut is vital for tone. The reasoning being the "greater the headstock angle the greater the downward pressure". I'm not Jonesing for a tone debate but I'm sure that's why keeps a 14 degree headstock angle even though they get lots of headstock breaks with their current design. It would be interesting if your Apollo could test for down pressure at the nut with the various headstock angles.

[@syriusgojiria9116]

Now that is really interesting lads ! A rig like this could also be the perfect place to test a variety of pickups and different position. Is it something you'd be interested to test too ?

[@normbarrows2]

Leo fender did that. Supposedly he used a similar rig to test pickup position vs harmonics along the string. IE how far the bridge pickup was from the saddle line, as that slightly changed the harmonic overtones the pickup detected. I've been tempted to test that myself. The closest I ever came was a magnetically mounted pickup you could place anywhere between the neck and bridge. I found best overall tone came from a pickup location about half-way between the bridge and middle pickup positions. But since then, I've continued to use just traditional neck and bridge positions on builds.

[@terrafree]

I wonder if measuring the force/displacement of a string laterally, like it would be if bending a note while playing, would have any effect on the results. Instead of stretching directly away from the fretboard as in this demonstration. If the orientation of the string seated in the nut slots, and the direction of the force applied may have any input change? With regards to the break angle as discussed. Someday I hope to try one of your guitars! :)

[@pedroleal7118]

I suppose there are too much variables...One , perpendicular direction, is enough to work with, for starters.

[@normbarrows2]

deflection is deflection. direction is irrelevant. extreme deflection is a different matter: you can't deflect below the fretboard, and extreme upward deflection will lift the string off the intonation point (front edge) of the nut.

[@tomdanielson2860]

Three by three tuners?

[@zaxmaxlax]

Aluminum tonewood, lovely 😂

[@GuitarQuackery]

Interesting gizmo, but I have a question. Can't all this be simply calculated, through engineerings, instead of measuring? In that case the Lab Rats would be able to build a virtual simulator. I'm also concerned that the measurements are off when measurements are made by lifting the strings up on the poker, as that method significantly changes the break angle across the nut.

[@Aeidotronics]

Thanks Ken. I think my eye just really wants the headstock angle to be right at where the strings first become parallel viewed from the side. Merry Whatever!

[@Jack_Plisken]

Was it the lab rats that recently created the replacement ribbon cables for the original Flys?

[@normbarrows2]

Based on the concept that "greater break angle = greater friction" at the nut (or saddle), it would seem that a system with a zero fret, guide pins instead of nut slots, straight string pull-through, and just enough break angle to keep the strings on the zero fret would result in minimum fretting and bending effort. Additional string above the nut or below the saddles should allow for additional elastic deformation, resulting in less effort for extreme bends. I actually did a build with no nut, a zero fret, and guide pins once - the Fender 12 build, a minimalist/experimental thing with a neck from a 1969 Fender Villager 12-string acoustic: kzbin.info/www/bejne/d17KmqiOaZh1qdE However, I tend to use locknuts on most all my builds these days, as it factors everything above the nut line out of the tuning stability equation. The real trick would be to come up with a locknut that doesn't need an Allen wrench, so tuning would be almost as fast and easy as with a regular nut - perhaps an all-6-at-once camlock system. Sounds like a job for a machinist! Additional after length can supposedly add overtones that may or may not be desirable. I've never found it to be an issue on any guitar personally. There are also claims that it has a positive effect on sustain. I have yet to look into that and suspect it's just BS: "bad science". I once made a rig like this to test the effect of afterlength on tone. 2 strings, same gauge, one with 1" after-length, one with 11" after-length. No effect on tone. Perhaps somewhat easier fretting - thin strings and low action don't require much fretting effort to begin with. Longer after-length = less bending effort. I didn't test for differences in sustain. I was interested in using long after-lengths and vertical roller trees to route strings to ergonomic tuner locations on tail-tuner builds.

[@amibenjo]

Wow! You are having so much fun in your work that in some parts of the world it might be considered illegal… What about headless designs? Are they considered as having an almost 90 degree pull on the strings as in a lute? Or minimum pull since they have no break angle?

[@chrispile3878]

Shouldn't you set the fixture on a surface plate for your most accurate measurements?

[@fepatton]

An interesting test might be to _hide_ the headstock angle from a player, but just _tell_ them you are changing it, and see if they perceive a difference. 🤔 Very cool jig.

[@kenparkerarchtoppery9440]

There's a fine idea, a blind study. It's an integral part of testing "this or that" on us humans, with all of our blind spots, prejudices, and pre-conceptions. It turns out that a credible test of sound or feel is an extraordinary thing to achieve.

[@S-T-E-V-E]

There's a lot of debate in the guitar world where a Fender Strat style inline Headstock is better reversed to have the longer string length past the Nut on the Bass strings as opposed to the traditional style! Any thoughts on this Ken?

[@BeauHannamGuitars]

Interesting- Was it a smooth linear difference of 2% from 4-80 degrees? What I take away from this is that with only a 2% difference between 4 and 80 degrees (!), there is absolutely zero reason to argue, worry or further consider the differences between 12 degrees (classical guitar slotted headstock) and 15-17 degrees (Typical steel string guitar range) in building in regard to the feel of string tension, assuming the nut is slotted well with minimal friction. Yet...-What would be interesting is if you did a *blind* test with the right hand on the strings between the 4 and 80 degrees- if you could consistently feel that 2% difference with the hand then that would be more interesting for builders and players. But as it is, 2% over 4-80 degrees doesn't mean much to me from an empirical standpoint.

[@magnograil6825]

Typically Baroque and Renaissance music does not use bending notes like used on guitars so the strings are not stretched as much and, of course, gut strings were used. Delrin is a poor choice for a nut as the wire wound strings will dig into it making it hard to tune. Incresing string tension by bending can cause the string to slide across the nut and change tuning. Fret positions have to be adjusted for the type of string and how far they are deflected to the fret since string tension changes with deflection.

[@jeffreywilliams6873]

Does anyone make any 6-in-line "Gibson robot guitar" tuners?

[@Matthew-tr6io]

Yup, the company that manufactured them for Gibson "Tronical Tune" still exists, and sells a variety of different versions for different headstocks etc.

[@PG-ex3kl]

It’s a ‘Lap-aluminium’

[@RIDICULOUSLOGIN]

So is the conclusion that the angle does make a difference but that it's insignificant to playability? 2% seems negligible.

[@kellygrant3074]

Zeroing the scale for each measurement seems tedious; perhaps an armature affixed to the frame with a dial indicator for distance, and a dedicated tension readout ,something along the lines of a neck jig, would eliminate the human error.

[@kellygrant3074]

Also, proximity to the nut changes the force and distance required to change pitch; this should also be a factor, or constant, in the equation. Also... Since the frets are on the bottom, shouldn't the force be applied from the top, so as to not change the break angle at the nut?

[@skullheadwater9839]

So, I see the jig or test fixture thing and I see how you can put the plastic stick with the scale and you can change the headstock angle but what exactly do you gain from all of the work and expense? Did you not already know if the headstock angle was increased the perceived string tension would increase? Don't misunderstand, I am a nerdy on geeky guitar stuff, but I am not sure what you gain in the archtop building front by spending time and money on this project. Have you not already built a bunch of guitars as well as knowing what others did before and therefore know where to start? I could see someone in 200 years trying to recreate a guitar with no wood using something like this except something you can play rather than just say "at this angle the pressure of a G string at the 5th fret is x-pounds to push the string y-millimeters" not sure if there is anything practical here. So, choose a headstock angle between 9 to 12 degrees and build guitars right? Just not sure what you learn from this which translates into real world building knowledge.

[@tommymaloney4167]

I can speak a little on this, I was actually the student who originally designed and built this whole fixture for VJ’s lab while I was doing my masters program. This fixture was intended to be able to prototype and test different components of a guitar quickly before going to a full body. The headstock, nut, pickups, and body were all designed to be able to be swapped in and out with those replaceable 3d printed “sliders” for easy adjustment At the time we were testing a tremolo system and different required forces to rotate it based off different cam profiles. This required lots of quick swapping of parts and adjustment of the system. It was much simpler to do with full access to everything in the rig like that. I agree it might be overkill for the smaller things they are testing in this video but as an overall prototyping platform it was highly useful for a lab that had a number of contrasting project going on at the same time. I’m glad to see that even to some extent it could then be helpful to Ken here