Changer Diameter Question

[Les Ford]

Can anyone tell me if there is a reason why changer diameter in all-pull guitars is typically 3/4 inch?
Is there any good reason not to make this 1 inch or larger? I was thinking that with a larger diameter the movement of the scissors and fingers could be reduced for the same amount of string pull?

[Ian Worley]

Conventional wisdom holds that a larger diameter is more prone to string buzz because of the flatter angle at the point where the taut string is tangent to the finger radius; a smaller diameter is more prone to string fatigue and breakage. There are certainly plenty of exceptions, but like most of the common conventions used in pedal steel construction, a lot of people experimented for many years through the '50s and early '60s with this and every other detail to arrive at what most folks seem to consider the optimal geometry. That said, it's worth noting that a whole lot of folks use bars that are 7/8" or even 15/16" diameter, which should theoretically behave the same as the finger in relation to a vibrating string, so there's that...

As far as reducing the required movement to accomplish a given change, the usual rules would apply re: leverage - a shorter pull will still be a stiffer pull, so there's no real advantage.

[Bobby D. Jones]

The finger radius arc is the last lever in the pull chain for raising or lowering a string. The larger the finger radius the more pressure it takes to engage the pedal or knee lever. The string does raise quicker, But needs more pressure which is uncomfortable and engaging knee levers can move the guitar around.

Some where in the pull chain, There may have to be a change made at another pivot point, For easy pulls and the guitar staying stable.

[J D Sauser]

Can anyone tell me if there is a reason why changer diameter in all-pull guitars is typically 3/4 inch?
Is there any good reason not to make this 1 inch or larger? I was thinking that with a larger diameter the movement of the scissors and fingers could be reduced for the same amount of string pull?

My answer may be judge as opinated, but...:

In theory, a tangential line takes off a radius at a "point".
A point in physics and line-construction a "point" has NO dimension, just location.

In reality, especially on a steel guitar, where the strings is being moved, pushed on, pulled, plucked etc, as the "V" markings indented on a changer finger over time will indicate... that "point" becomes more of a line.

That line does a lot of undesirable things:
- It creates buzzes
- it eats up energy (sustain)
- wears the string at that point (why it brakes there and like toilet paper NOT at the dotted line! )
- it creates intonation issues as the scale length is unstable due to bar pressure.

The larger the radius, the worse these adverse effects are.

When you look a non-pedal steels and most ANY other stringed instrument, you will find that the bridge is the "Holy Grail" and mostly has the sharpest possible edge.
I think the round changer-"bridge" is the item that has the most detrimental influence on a PSG's sound compared to a quality non-pedal steel.

... J-D.

[John Hyland]

I think that’s a good argument JD. But the good thing about a roller bridge is it is gentle on the string.and associated breakages. It is also probably easier to make than a straight line pull and relax style. That said it wouldn’t be hard to have “half” roller where the front quadrant drops away. But again more stress on the string.

Can anyone tell me if there is a reason why changer diameter in all-pull guitars is typically 3/4 inch?
Is there any good reason not to make this 1 inch or larger? I was thinking that with a larger diameter the movement of the scissors and fingers could be reduced for the same amount of string pull?

My answer may be judge as opinated, but...:

In theory, a tangential line takes off a radius at a "point".
A point in physics and line-construction a "point" has NO dimension, just location.

In reality, especially on a steel guitar, where the strings is being moved, pushed on, pulled, plucked etc, as the "V" markings indented on a changer finger over time will indicate... that "point" becomes more of a line.

That line does a lot of undesirable things:
- It creates buzzes
- it eats up energy (sustain)
- wears the string at that point (why it brakes there and like toilet paper NOT at the dotted line! )
- it creates intonation issues as the scale length is unstable due to bar pressure.

The larger the radius, the worse these adverse effects are.

When you look a non-pedal steels and most ANY other stringed instrument, you will find that the bridge is the "Holy Grail" and mostly has the sharpest possible edge.
I think the round changer-"bridge" is the item that has the most detrimental influence on a PSG's sound compared to a quality non-pedal steel.

... J-D.

[Les Ford]

This is getting interesting.
What are the other options that would allow for a straight pull and relax without a pivot axle setup? I have looked at the Fender blade setup but it looks overly complicated and has limited raises and lowers.

I think that’s a good argument JD. But the good thing about a roller bridge is it is gentle on the string.and associated breakages. It is also probably easier to make than a straight line pull and relax style. That said it wouldn’t be hard to have “half” roller where the front quadrant drops away. But again more stress on the string.

Can anyone tell me if there is a reason why changer diameter in all-pull guitars is typically 3/4 inch?
Is there any good reason not to make this 1 inch or larger? I was thinking that with a larger diameter the movement of the scissors and fingers could be reduced for the same amount of string pull?

My answer may be judge as opinated, but...:

In theory, a tangential line takes off a radius at a "point".
A point in physics and line-construction a "point" has NO dimension, just location.

In reality, especially on a steel guitar, where the strings is being moved, pushed on, pulled, plucked etc, as the "V" markings indented on a changer finger over time will indicate... that "point" becomes more of a line.

That line does a lot of undesirable things:
- It creates buzzes
- it eats up energy (sustain)
- wears the string at that point (why it brakes there and like toilet paper NOT at the dotted line! )
- it creates intonation issues as the scale length is unstable due to bar pressure.

The larger the radius, the worse these adverse effects are.

When you look a non-pedal steels and most ANY other stringed instrument, you will find that the bridge is the "Holy Grail" and mostly has the sharpest possible edge.
I think the round changer-"bridge" is the item that has the most detrimental influence on a PSG's sound compared to a quality non-pedal steel.

... J-D.

[John Hyland]

This is getting interesting.
What are the other options that would allow for a straight pull and relax without a pivot axle setup? I have looked at the Fender blade setup but it looks overly complicated and has limited raises and lowers.

The tip of a pivoting lever only needs to move a small amount to retune a string so the arc of movement is for all intents and purposes is nearly a straight line so I guess the tip of the fingers could still perform a similar function. Since the fingers hang off the axle removing or relocating the support is a problem to overcome.

[Bobby D. Jones]

I saw a picture not long ago somewhere on the Forum or the internet.
I do not remember if the guitar even had a name.
What was interesting was in the top of each changer finger was an angled milled indentation. From the picture there was no smooth roll over the finger, But the string was not touching the finger once it reached the milled indentation.

I could see where this would cut down some of the problems with the rounded finger, But the string bending in a small area as it leaves the the sharp edge, Would place all the bend in such a small area on the string. This would cause quick work hardening of the bending string and shorten the life of the string.

I have seen pictures of some guitars that have a lever that pulls the string held by the ball with no bending in the string. But then there is another set of rollers, Just in front of the changer fingers to set the scale length. This would make more work for the Manufacture, And more problems to maintain the guitar when playing every day.

When I built a steel guitar about 1970, I worked in the light bulb industry. We had a mechanical engineer on our shift to help with machinery and actual assembly of the bulbs. The engineer and I discussed the curve on the changer fingers. His theory was, It was not perfect, But it worked and saved adding a lot of parts to the system.

[J D Sauser]

This is getting interesting.
What are the other options that would allow for a straight pull and relax without a pivot axle setup? I have looked at the Fender blade setup but it looks overly complicated and has limited raises and lowers.

I think that’s a good argument JD. But the good thing about a roller bridge is it is gentle on the string.and associated breakages. It is also probably easier to make than a straight line pull and relax style. That said it wouldn’t be hard to have “half” roller where the front quadrant drops away. But again more stress on the string.

Can anyone tell me if there is a reason why changer diameter in all-pull guitars is typically 3/4 inch?
Is there any good reason not to make this 1 inch or larger? I was thinking that with a larger diameter the movement of the scissors and fingers could be reduced for the same amount of string pull?

My answer may be judge as opinated, but...:

In theory, a tangential line takes off a radius at a "point".
A point in physics and line-construction a "point" has NO dimension, just location.

In reality, especially on a steel guitar, where the strings is being moved, pushed on, pulled, plucked etc, as the "V" markings indented on a changer finger over time will indicate... that "point" becomes more of a line.

That line does a lot of undesirable things:
- It creates buzzes
- it eats up energy (sustain)
- wears the string at that point (why it brakes there and like toilet paper NOT at the dotted line! )
- it creates intonation issues as the scale length is unstable due to bar pressure.

The larger the radius, the worse these adverse effects are.

When you look a non-pedal steels and most ANY other stringed instrument, you will find that the bridge is the "Holy Grail" and mostly has the sharpest possible edge.
I think the round changer-"bridge" is the item that has the most detrimental influence on a PSG's sound compared to a quality non-pedal steel.

... J-D.

I think most of us would think that. Then Excel came along with a pointed ("hump") changer finger and even on 25.5 scale guitars it does not seem to break strings more than anybody else's. Given, they their lower travel is horizontal which would seem to reduce the bending stress.

Only few PSG makers have opted for 1" changer fingers. I think the last I saw 25 years ago was a Flynn (by Harold Flynn, if I remember right?).

IF string stress really is a concern over tone, there is the Williams changer finger with the lesser bend, maybe worth while considering?

... J-D.

[Jack Stoner]

Paul Franklin Sr, in one of my many talks with him, stated his larger diameter changer axle contributed to less detuning.

The larger diameter axle did not contribute to any playability drawbacks or to any string buzzing.

[J D Sauser]

Paul Franklin Sr, in one of my many talks with him, stated his larger diameter changer axle contributed to less detuning.

The larger diameter axle did not contribute to any playability drawbacks or to any string buzzing.

That’s the changer AXLE/SHAFT on which the changer fingers pivot.
Most any unsuported changer design like the Emmons, old MSA, Zum etc all had thicker changer shafts than guitars with supported changer shafts like the Sho-Bud or Carter.
Unless I completely misunderstood the OP, the subject here is the changer FINGER’s “diameter”… or better radius.
Franklin PSG has the same changer finger radius as most modern PSG.

… JD.

[John Hyland]

Paul Franklin Sr, in one of my many talks with him, stated his larger diameter changer axle contributed to less detuning.

The larger diameter axle did not contribute to any playability drawbacks or to any string buzzing.

That’s the changer AXLE/SHAFT on which the changer fingers pivot.
Most any unsuported changer design like the Emmons, old MSA, Zum etc all had thicker changer shafts than guitars with supported changer shafts like the Sho-Bud or Carter.
Unless I completely misunderstood the OP, the subject here is the changer FINGER’s “diameter”… or better radius.
Franklin PSG has the same changer finger radius as most modern PSG.

… JD.

True but the OP was asking about finger size but a larger axle makes a larger finger

[J D Sauser]

Paul Franklin Sr, in one of my many talks with him, stated his larger diameter changer axle contributed to less detuning.

The larger diameter axle did not contribute to any playability drawbacks or to any string buzzing.

That’s the changer AXLE/SHAFT on which the changer fingers pivot.
Most any unsuported changer design like the Emmons, old MSA, Zum etc all had thicker changer shafts than guitars with supported changer shafts like the Sho-Bud or Carter.
Unless I completely misunderstood the OP, the subject here is the changer FINGER’s “diameter”… or better radius.
Franklin PSG has the same changer finger radius as most modern PSG.

… JD.

True but the OP was asking about finger size but a larger axle makes a larger finger

The finger radius on a Zum, Emmons, Franklin, old MSA etc… all guitars with unsupported (no ribs, no center support) larger dia. changer shaft is none bigger than on unsupported smaller changer shaft dia. guitars like ShoBuds, Carter, ShowPor etc guitars.

Frankly, I don’t remeber if the few guitars which had 1” dia. changer FINGERS (1/2” rad.) had supportet or unsupported changer shats as these guitars were not only few as brands but seemed to have enjoyed little popularity and thus were rather rare to see.

I will will note state that the larger changer finger radius alone is to blame for the fact that guitars including that detail have not seemed to attract a huge followship, but I would insist that it’s not just an suspicion but a clear geometrical and domonstrable mechanical effect that the larger a changer finger’s radius, meaning the “flatter” a string “take-off” surface, the more noticeble intonation issues and string-energy LOSS (aka. dynamics & sustain) we will get.
Intonation issues are not astrange to steel guitar due to the varying effects of bar pressure along the scale on different gauge strings. As strings suffer pressure are pushed down, not only their tension raises, but the angle at whitch et meets the bridge. On a “clean” or “sharp” bridge, as found on most stringed instruments, the later has a negligable effect, but on an large radius, the tangent angle changes rolls the sting on that surface a shortens the effective remaining string length furter raising the pitch… an undesirable effect described as intonation issue.

The ideal, for tone, sustain, dynamics, cleaness of sound (buzz reduction) and overtone richness is a “clean” edged bridge as found on most stringed instrument before the PSG.


… JD.

[Donny Hinson]

As I recall, Buddy Emmons once credited the smaller radius changer fingers as one of the characteristics that gave the Emmons guitars their sustain and sound.