Crazy project #1: variable-pitch pullrods for JI tuned PSG.

[Georg]

I'm attacking those unusable pedal combinations and sour chords associated with "sweet" or "Just Intonation" tuned PSGs, by introducing "variable-pitch pullrods".

One method for changing the length of pullrods for one pedal "on the fly", based on which other pedals are pushed, is to use a free-hanging lever on a bent bellcrank axle and connect two halves of a pullrod via it. Somewhat like what's shown in this sketch...


Two such levers that looks like bellcranks, are shown rotating freely on a round axle, and since the axle is bent and the in and outgoing pullrods are offset, the angle the axle is rotated to by its locked "angle control bellcrank" that is connected to bellcrank shafts for other pedals, determines the effective length of the pullrods for this pedal.

"A" shows the bent axle i what I call "normal pitch" position.
"B" shows the bent axle in its extreme left position for "lowest pitch".
"C" shows the bent axle in its extreme right position for "highest pitch".

I expect a rotation of max +/-45° off neutral to me enough to cover the necessary pitch range for JI tuning of an activated pedal in any pedal combination, since no pitch adjustment larger than +/-20 cents should be necessary.
I will use adjustable end-stop screws to control and tune the pitch for max angle both ways - shortest and longest pullrods, but haven't decided if I should spring-load it for "normal pitch" or even if a "normal pitch" is needed. I have found "2-pitch pullrods" to be enough when testing on my old Dekley, which means simply using a spring to pull the angle back to an end position may be enough.

Since the length of the freehanging bellcranks and the angle controlling bellcrank is about the same as normal bellcranks in a PSG, the force needed to change pitch will be very small.
Since the variation in length of the pullrods is very small, +/- a millimeter or so should be enough, such a variable pitch changer has to be as precisely made and moving as a regular bellcrank axle, but it can be made thinner and lighter because of the low load that will be put on it.

I will need one such adjustable pullrod in my Dekley to begin with, to control pitch of string 5 and 10 with A pedal engaged. I expect 2 or 3 such angled axles to cover all, or nearly all, "unusable" chords in a regular JI tuned E9 PSG.

Now, I'll be really happy if any of you can find the flaws in my logic so far. Got to be some, and I want them to be found and corrected early...

[Allan]

Holy bat poop! I think that would work. I do have a question though. Well, more than one actually. How would you calculate the offset in the axle? (or would it really matter if there were limiting screws included in the design?) Would a change in string gauge affect the amount of swing that the offset would need to describe to keep things right? (or would it really matter if there were limiting screws included in the design?)

Georg, that is fascinating. More please.

Allan.....

[Georg]

Allan, the offset matters of course, but it's easy to get it well within range without calculating too much since I can tune those stop screws.

Actually, I want to thread the freeswinging bellcranks onto the axle - not make them two-parts bellcranks, and plan to use tubes to keep them and the two pullrod-parts lined up nicely. For this reason I think it is best to clamp, or screw, the axle-ends offset on a straight rod. A few more parts needed, but it'll also provide for adjustable offset.

Changing string gauge will affect this "variable pitch" as much as it affects the regular pedal tuning - it needs retuning. It may (also) be necessary to have slightly different offset for tuning two rods to perfect pitch-offset on the same axle - think of string 5 and 10 which must be kept in sync. So, I'd like to be able to "offset-tune" both ends individually.

Just throw in more questions. I'll post more sketches as the finer details become clearer. I aim to make this "variable pitch" light, stable, and easy to retrofit on most all-pull PSGs - not just mine.

[Allan]

Bwaaaaaaahahahahahahaaaaa...

Mechanicals! Nah! Here's how to do it.

electronic PSG.jpg (17.94 KiB) Viewed 1414 times

Conceptual only at this stage but the technology exists already (check out the Gibson Dusk Tiger for an example of the basis of the way to go)

The onboard software could be configured so as to allow for near instant re-tuning between songs - just select a key with a button.
The external software could allow for simple changes in pedal/lever config.

The drawing is concept only. I have actually taken the thing to a further stage in other drawings but this is enough to show the basis of it all.

I do need to say that I think your cranked axles are a really great concept.

Regards, Allan.....

[Georg]

Weeeeeee......

Hmmmm ... a bit late, me thinks. I solved the software side of it back in 96. Will of course have to reprogram to go with new electronic hardware - PICs/CPUs etc., in case I ever bother building a servo-driven PSG. Not my first priority at the moment, but one will be built by someone one day soon no matter what.

That "string pulled around a roller" solution is sure to break strings in no time on a PSG, by repeatedly bending them. At least go "linear".............


A PSG don't need tune-up to different keys - just place the straight bar off-fret as you play ... you all do that already, don't you? Works perfectly everywhere but in open - zero fret - position, and lots of things - like bar-vibrato for instance - don't work in open so it's not a big deal.

Also, it is those sour-sounding and useless pedal combinations that need re-tuning to resolve into themselves across all 10 or more strings also in JI tuning. Retuning the entire PSG for different keys won't in itself solve any JI-related pedal conflicts, it just moves them around in circles.


Only keyed instruments really need key-change buttons. Having a JI tuned grand piano would be nice. Software, no problem - much easier than for a PSG, but do you think today's servos could pull that off?

[Allan]

Weeeeeee......

Hmmmm ... a bit late, me thinks. I solved the software side of it back in 96. Will of course have to reprogram to go with new electronic hardware - PICs/CPUs etc., in case I ever bother building a servo-driven PSG. Not my first priority at the moment, but one will be built by someone one day soon no matter what.

That "string pulled around a roller" solution is sure to break strings in no time on a PSG, by repeatedly bending them. At least go "linear".............


A PSG don't need tune-up to different keys - just place the straight bar off-fret as you play ... you all do that already, don't you? Works perfectly everywhere but in open - zero fret - position, and lots of things - like bar-vibrato for instance - don't work in open so it's not a big deal.

Also, it is those sour-sounding and useless pedal combinations that need re-tuning to resolve into themselves across all 10 or more strings also in JI tuning. Retuning the entire PSG for different keys won't in itself solve any JI-related pedal conflicts, it just moves them around in circles.


Only keyed instruments really need key-change buttons. Having a JI tuned grand piano would be nice. Software, no problem - much easier than for a PSG, but do you think today's servos could pull that off?

It's not 'late' 'till someone builds one.!
And, as you say, someone will - I actually believe one is underway. I base that statement on something someone said in a thread on the PSG forum sometime ago.
As far as placing the bar 'off-fret' - LOL - I don't 'cause I don't have a PSG! But I know what you mean. All players do that to an extent even if they don't admit to it. Parallax sees to it that they do. However, when I was talking about retuning for different keys I was think about the fact that X# and Yb are not exactly the same thing.
Regarding the sour/useless combinations: On my sketch I only showed a single motor and a single string. That motor would be used for the PSG functions only. Tuning would be done with a separate motor which would also be used to correct the sour aspect of the string combinations. I take your point regarding linearity of pull. In practice I would probably go for something like a powered version of a pull/release changer.
As far as hardware goes, today, yes, suitable stuff does exist and is available. I don't know about cost for setting up your concert grand with it's triple basses and stuff but, in the realms of 'possible and existing', yes, it exists and would do the job.

Do you think we need to ask Larry to open a 'So Far It's Just Fantasy' section here in the forum?

Keep 'em coming Georg.

Regards, Allan.....

[Bent]

Yesss! to a 'So Far It's Just Fantasy' section. I'm serious. Imagine the contraptions people would show us!

Georg, you know by mow that I don't have anything to add to this thread which is way over my head. As y'all know I am still learning to tune ET and to build PSG the usual way. That said, you also know that if any of you come to me and say "build this", accompanied with drawings and liberal explanations, I will be there with bells on.

I am starting to comprehend what you are drawing and explaining. Question: Will all this added stuff be instead of or in addition to, the compensators and other sundry items already in place on a steel in order to chase that perfect intonation/tuning?

I applaud your, and others' innovations in this field. Actually I am envious when I see that I should understand when I don't. Call it age catching up with me. In anything we make, and improve upon, we have to remember that Model T Fords can't be around forever. I will gladly admit that I am one of those who seem to wanna keep the model T around for a few more years. Because.....

When is the last time any of us heard a song where one of our heroes are playing on or any non-hero accomplished player for that matter, where the steel is out of tune or even a few cents off from the JI or whatever.
We all agree I am sure, and Georg said as much not long ago: Lloyd Green's playing is "pure gold". I take that to mean that you did not hear any sour notes there(it was a live situation)

So in the context of this thread the question begs to be asked: Why are we chasing after something that is almost un-attainable,and since the masters crank out one sweet-sounding song after the other according to the tried methods is it really worth it for the masses? Are we doing it just for our own satisfaction? Just for our own so-called perfect-pitch ear? Are we building a pedal steel that will be embraced by the masses or are we building one that only we can understand, like the looks of(i.e. no shiny parts) and sit there in our own smug world and play it in our music room?

With that piece of what some might say negativism off my mind, I say, carry on! I will most definitely devour every word and who knows, down the road, I might even learn enough to offer intelligent suggestions!

[Ross Shafer]

Hey Bent,

Great post...I don't think it was negative at all. There's nothing wrong at all with keeping perspective.

Nor is there anything wrong with a passion for detail and the challenge of chasing down the elusive.

[Georg]

Do you think we need to ask Larry to open a 'So Far It's Just Fantasy' section here in the forum?

What for..?

As far as I'm concerned it's all about real-world research and design.

FYI: I had a pitch-correction gismo (rod shortener) on my PSG for over a decade, but took it off because it didn't release perfectly, and because it was only tunable with a hammer. I prefer adjustment screws...

"Fantasy" would be more like if someone said they got beat-free chords out of ET tuned instruments, or claimed that all chords on 12 tone/octave single-key JI tuned instruments are beat-free.

We all agree I am sure, and Georg said as much not long ago: Lloyd Green's playing is "pure gold". I take that to mean that you did not hear any sour notes there(it was a live situation)

I don't hear any real sour notes there, and neither do I hear any in the hour long live recording I made nearly two decades ago. Can easily hear the unavoidable beating in some chords, and a few misses and near-misses though.
I don't expect anything else, and would probably be disappointed if Lloyd played "non-humanly perfect". Would be less music left, I think...
Would also surprise me, and all with good "relative ear", if Lloyd all of a sudden had "solved" all problems with beats. The best musicians and mathematicians, and a lot of more ordinary people, have looked into all that for at least the last 3000 years . Can't be "solved" since it's in accordance with the law of nature - only made to sound good/right (or whatever term one prefers).

Lloyd Green is, IMO, a genius in selecting and playing the notes/pitches that sounds right for whatever he wants to express, and to avoid those that don't fit. Just look at his copedent ... it is reduced to a point where most pitch-conflicts are avoided.
So, yes, I think Lloyd Green's playing is "pure gold". To me he is the dominant inspirational force when it comes to musicality, and in fact the sole reason I play steel guitar at all.

Now, I think we shall return to the subject at hand, which is about designing mechanics to solve pitch-conflicts on our own JI tuned PSGs, and let Lloyd tune and play his the way he wants. He's good at it...

Question: Will all this added stuff be instead of or in addition to, the compensators and other sundry items already in place on a steel in order to chase that perfect intonation/tuning?

I'll start by adding parts to the existing mechanics on my own PSG, simply because I don't want to rebuild it all from scratch at this time. Once the problems are solved all sorts of variants can be built for/by those who think they need such gismos.

While researching and designing such add-ons, I am looking into ways to completely replace big chunks of existing mechanics with its fixed-pitch bellcranks, splits and compensators, with conflict-solving variable-pitch solutions better suited for optimal JI tuning also for much more complex copedents than mine. Can't put it all in one thread though

[Georg]

Bent, since you have built a couple of PSGs from scratch: how difficult would it be to introduce "movable holes" for those bellcrank axles?
I know that sounds funny - even ridiculous - so it is OK to laugh

To explain: if it is possible to move the nylon bushings for both ends of the bellcrank axles approx. +/- 1 millimeter towards and away from the changer - 2 millimeter in total, it'll offset the axle and thereby change the pitch for activated pedal enough to achieve the variable-pitch pullrods effect I'm after without adding extra axles and stuff.

I'd use a kind of angled levers made out of 3 mm aluminum plate to "move the holes" so to speak, and lay these levers flat along the sides under all axles (with the PSG the right way up) so they can interact directly with adjustable "cams" (modified bellcranks) on other axles on-the-fly. This means the two axle-ends can be adjusted individually, so two bellcranks on the same axle can be pitch-tuned in perfect sync.

It will also be possible to let "cams" on one axle work with or against "cams" on another axle on the same lever for more complex pitch-adjustments, by using two-stage spring-loaded "cams", and the "cams" and the long levers will obviously be placed well outside the pullrod "path" and be very accessible for adjustments. Steel-enforcement on the aluminum lever edges that'll be worn down by the cams, should secure long life.