Guitar - where to place the origin(s)?
@TheCADWhisperer wrote:you want a rock solid point that doesn't change - a place you can use as reference for everything. (or most everything)
Attach image here of something from the real world that is similar to what you want to design.
(I'll assume I don't know what a Guitar is, as it doesn't really matter.)
And that rock-solid point is exactly what I am looking for. I have attached a deliberately silly screenshot of a cross-section of the relevant geometry, which is a slice through the center of the neck.
I think I have discovered some context to what you were talking about, putting the datum in the center of the back of the body. If accurate, then I can confirm that we are talking about completely different things. I found this here: https://www.gitarrebassbau.de/viewtopic.php?f=10&t=6
In my original post, I mentioned that most (if not all) of the online content around electric guitars and CAD is in router templates. Well, this is pretty much that.
I am definitely not asking about router templates or body shapes, and I can see how someone might have been confused, because that is literally the entire library of guitar CAD content on the internet, as far as I have been able to find.
To reiterate, I am interested in creating a parametric 3D guitar. I want to fully define the functional geometry based on scale length, and I have assumptions about where the origin should be, but I would like to hear from subject matter experts to support or debunk.
Hi,
The good news is that I actually DO know a thing or two about guitars and I HAVE modeled or are modelling them in
Fusion. I feel your pain about how to go about it but now having done it and worked out a bunch of stuff I think I can
help.
I am in the process of modelling a 1953 Fender Telecaster. I have access to one and have got a whole bunch of
measurements and I am putting it all together. Here is what I have come up with so far.
I am using the Born technique basically as guitars are a bunch of interconnected parts. While I know exactly what
you are saying about various relationships, I think you are overthinking a couple of things.
The body I have modeled with the bottom of the guitar at the origin. While it is not the case with a telecaster that
it is symetrical, because it is not an offset neck then centre of the cutouts and the neck pocket will all be on the centre
line of the body. I considered extruding above and below the XY plane with the neck pocket being on the plane but
decided that all cutouts and routs would be relative to the top so I ended up extruding down. The shape I modeled
from an overhead photo with splines.
If I was doing something with a curved top then I would model the curve separately and join it to a normal extruded
body. I would keep the origin and probably extrude the body down and use the plane to cut through where the curved
top joins the rest.
I would recommend model ALL other parts on the origin using the Born technique as I did then use joints to put it
all together.
Starting with the neck. If you plan on CNC machining the entire neck then I would model it FLAT as this is what it will
be WHEN you install the Truss rod. The truss rod is there for this very reason, to remove the curve from the neck from
the tension of the strings. It will be almost impossible to design a neck with a curve as all timber will be different,
and it will not matter anyway because when set up it will be straight.
I was just modelling the guitar for practice, but if I was actually going to build it then I would design the neck and
fretboard as the neck assembly in two pieces. This way I would be modelling it the way I would be building it by
joining the fretboard to the neck with glue. In reality I would have to use clamps to get it to sit correctly before it
was installed and the truss rod adjusted. It will still be straight when set up, the curve of the fretboard will not
change and the string height will not change.
The fretboard should be easy as the fret distance is a mathematical relationship. You can set this up as a parameter
so you just enter 21 or 22 frets (in the case of Fender), make the top of the fretboard the correct radius and the
bottom flat to glue (join) onto the neck.
The Nut is just a big fret so cut the hole then model the nut separate to the fret wire for the frets. I would also
use the born technique and joints.
Tuning machines are a choice you will have to make. How realistic do you want your model? You can model the
open style like Waverly
or these closed or locking type. Your model so if you want open gears 18:1 ratios and such then model them as normal
Use the Born technique and origin and use joints to put them in the modeled holes of the neck.
Some detail is available on the net. Stewmac provided this drawing for a traditional tele "Ashtray Bridge".
There are a few of these type of things available. I usually get a drawing like the above and make my own model in
Fusion.
Some things you will not be able to model exactly. You can model springs in the bridge but getting them to work
as you adjust them is difficult and not worth the effort. Similar to winding the strings around the tuners. getting the
string to wind around the tuner as you turn the tuner is not worth the effort.
Some things in your model you can do, like have the strings pass through the ferrules in the body through the body
and then over the bridge to the nut then to the tuners, but getting it any more than looking right will be a challenge.
This is a great challenge to model, but just think about what CAN I model, WHY I might need to model things a certain
way then just sit down and go for it. I think you got a bit into overthinking things like the neck bends when not under
tension. Sure, you and I know that is what happens but the end result is it is straight when under tension and the
truss rod set correctly. The strings will be the correct distance above the fretboard if you model the nut, the bridge and
the neck to the correct radius.
Modelling pickups will always ever be a shape with some simulated wires. Everything else is straight forward, but
all of the distances and radii are just details you have to get right. You should be able to model most electric guitars
in fusion. Some will be harder than others but all could be taken to CNC level, even if ultimately some has to be hand
finished. Fender has a LOT of people who hand finish parts of their guitars in the factory, mainly because timber is
always different, even from the same tree.
Hope this has helped a bit. I am happy to give you more advice if you need it.
Cheers
Andrew
Wow! Thank you for that very thoughtful and detailed post!
As a possibly better illustration in context, in the screenshot below, I have placed a sketch in the YZ plane, which could be considered a slice through the neck centerline. The sketch line is representing a 24" string, and the construction line and plane represent the top of the fingerboard. Perpendicular from both ends of the string line are construction lines that represent the height of the nut and the height of the saddle, as offsets from the string line. Arbitrarily, one is 4mm and the other is 8mm, but they could be anything.
This is only one of several scenarios and considerations. The datum could be on the twelfth fret, or the nut or even the junction between the nut and the fingerboard. In any case, the offset lines described above could (and maybe should?) be perpendicular to the fingerboard instead of the virtual center string.
The reason any of this matters is because I want to design the guitar without considering cosmetics at all, as a parametric object, whose aesthetic does not affect how it works. How it looks is literally the last thing on my mind at this stage of design. Manufacturability is also important, and I have a CNC router I special ordered from Avid that has just enough of a work envelope for any conceivable guitar component. It's a wide-shallow "Benchtop Pro" machine, which is not officially in their catalog. It lives in my apartment in San Francisco, which is nuts.
I might be totally wrong about my assumptions about guitar string fixture geometry. I might be defining a guitar wrong. I'm here to learn from those who know.
