Raise hole choice and required lower return spring tension

[Glenn Demichele]

How does the choice of the raise hole affect the required tension on the lower return spring? (I know that if the lower return spring is too loose, the raise can move the lower finger off of its stop).

[Ian Rae]

I don't think it makes any difference.
The required strength of the return spring depends on the tension in the raised string, regardless of how it got raised.

[Ian Worley]

I think it would depend on the geometry of the specific changer design, but in theory it shouldn't make any difference. In a typical modern all-pull changer the energy of a raise pull is always directed to the pivot rivet, regardless of its location along the lever (i.e. which raise changer hole you use). Typical lower return spring adjustment should be just a little more tension than is required to minimally hold the lowering scissor firmly against its stop when you engage a raise.

Lowers are a little different. In addition to making the pull more stiff, too much lower return spring tension can cause the pull rod/nut to become a secondary fulcrum, allowing the raise finger to lift and partially negate the lower. Raise helper springs can also create or exacerbate this problem, where lower return spring tension holds the lowering scissor against the stop just fine on a normal raise, but allows the raise finger to partially engage on a lower.

[Bobby D. Jones]

If a string only raises, It only requires the lower return spring to be tight enough, To hold the lower lever against the stop bar. Once it holds the lower bar on raise, How tight don't seem to matter.
If the string raises and lowers, Now the lower return spring has to hold the lower lever against the stop on a raise, But it has to be long enough and have proper tension, To allow the lower without the raise lever moving off the stop bar.

I joke about it. Mechanics of a PSG is easy. When you get the lower return spring figured out, On Strings that raises and lowers. You get nominated for your PSG Wizard Wand.

[Donny Hinson]

If a string only raises, It only requires the lower return spring to be tight enough, To hold the lower lever against the stop bar. Once it holds the lower bar on raise, How tight don't seem to matter.

Not only that, but if a string isn't lowered, no lower-return spring is even required on that string! You can substitute a piece of wire to hold the lower finger in position. I do that on certain changers, notably the older MSA Classic ones that do not have the reliefs cut in the raise fingers. This makes the full-tone raise possible whenever I have trouble raising the F# (1st string) a whole tone.

[Glenn Demichele]

Thank you so much guys! I got my guitar working OK after some minor rodding changes (to stop some rod rub and time some pulls better), and I noticed that I had to tighten the lower return springs, which I don't think I had to do before. I guess it was either always out-of-whack, or the lower return springs are weakening, or some other mystery issue (!).
I get how the raise hole wouldn't matter because the force ends up on the rivet regardless of the hole selected. I did move a rod and retune it to see if it made any difference in the pull return spring adjustment required, but it did not.

This maybe isn't related to my raise question, but I lubed the heck out of the changer, and things are very very slippery until I load the changer with a string. When I tune a string up to pitch and make the lower return spring too loose, it of course doesn't have enough pull against the string tension to fully return to the stop after a lower, say for example it returns to 2mm away from the stop. If I then move the pull lever with a screwdriver and let go, one would expect that in a perfect frictionless world that that lever would return to that 2mm position again, where the string tension again is balancing against the spring. What I see is that when I move it with my screwdriver, it just sticks where I move it to. I can pull it 4mm from the stop, let go, and it stays there. i can push it all the way to the stop and it stays there. Is this friction on the axle? Maybe it's OK, but I have to tighten the pull return springs pretty much to overcome this friction to make it return to the stop after a pedal pull. My springs are maxxed out on the E9 pedal C raises.

[Donny Hinson]

Do this:
Remove the string and the lower return spring. Then move the changer finger with your finger. It should move back and forth effortlessly. Now, hold the raise finger and see if the lowering finger still slides back and forth easily. If it doesn't, the finger is gummed up and will require some cleaning and relubing. More often than not, it's the finger being gummed up that causes the problem, not the changer axle.

[Glenn Demichele]

Thanks Donny: Yes, with no string and no spring, both the raise and lower fingers move very freely against teach other and the axle. When I add the string and the spring, but no rods, the lower lever gets “sticky”, where if I push it, I can move it but stays where I leave it. If I move it father,, it comes back toward center but sticks before it gets to the balance point.

[Ian Worley]

It does sound like you might just need a little more tension on the return spring(s) so they return reliably, but perhaps I'm misunderstanding what you're saying. Springs do lose strength over time, but that state of relative equilibrium you described in the lowering scissor where it kind of stays where you put it typically just means you need to tighten the spring (assuming the scissor still moves relatively freely without grinding or binding when you push it or pull it).

Keep in mind that the leverage is very different on the return spring side of the equation vs the string side, it's not a 1:1 relationship. String tension is pulling directly on the finger, but leverage is based solely on the radius of the finger, which is relatively short. The return spring is pulling on a much longer compound lever with typically two intermediate pivot points between it and the finger, so there are more mechanical interactions where additional friction could arise. If something is binding or hanging up it's more likely here as Donny suggested, and not likely at the axle. The string pulls the finger in a linear fashion, perpendicular to it, whereas the return spring is essentially pulling off-center because the lowering scissor pivots off one end of an otherwise unsupported rivet that connects it to the raise scissor next to it (typically). If the rivet or its holes are worn or loose it would skew under tension such that it's no longer perpendicular to the holes it rides in, creating additional friction.