Bellcrank-Pullrod-Changer finger slot and hole relationship

[A. B. Traynor]

Could anyone explain the logic behind the selection of which slot in the bellcrank and wich hole in the changer finger is used? Also what problems would you encounter if the slot/hole relationship is out of whack? Thank you in advance.........steel on!!

[Hans Holzherr]

Think of a continuation of a pull rod past the changer finger it's hooked to. The more this line points upward, the shorter the travel and the harder the pedal/lever. The more it points downward, the longer and softer the pedal/lever. Parallel pullrods may yield similar, but not equal results between the extremes.

[Hans Holzherr]

Improper rodding can result in suboptimal pedal/lever action and/or not all pulls on a pedal/lever starting at the same time as they ideally should.

[Pit Lenz]

Hans is correct. (Edit: and fast...)
In detail:
Pullrods should have just a little slack when no pedals or levers are activated.
If you have two or more pulls on one pedal or lever, you want them to start (hit the raiser/lower finger) and end (finish the pull at the correct pitch) at the same time. Different string diameters require a different pull travel. This can be achieved by choosing the right hole combination.
Also, some people use a pull of a second string as a feel half stop for another string. This means that the second string's pull starts right when the first string's raise has reached a halftone and they continue to -let's say- rise another half from there. In this case the right choice of bellcrank hole combinations is crucial.

[Lane Gray]

Ummm, Hans? The softest, easiest pull should happen with a parallel pull at the topmost hole and the stiffest with a parallel pull at the bottom, no?
I understand it as a function of leverage, with the holes closest to the shaft and changer doing less work (I.e. less resistance) for given pedal travel.

And the aim is twofold: to have the softest pedal (some like them stiffer) and to have multiple pulls start and end together (unless a half-stop is desired)

[Hans Holzherr]

The softest, easiest pull should happen with a parallel pull at the topmost hole and the stiffest with a parallel pull at the bottom, no?

No, the stiffest and shortest is the combination of the longest bellcrank lever with the shortest changer finger lever. This results in a direction of the pullrod which is hardly parallel to the top.

[Tony Glassman]

It's all about mechanics (Newtonian physics): There are 3 factors of leverage:

1] FORCE (or effort to do the work)
2] FULCRUM (pivot) placement
3] LOAD (what is being moved)

Basically, leverage is all about the placement of the Force and Load in relation to the Fulcrum.

The farther the Force and closer the Load is to the fulcrum.....the easier the effort. The trade off is that the length of travel increases. Think of a teeter totter with 2 kids of equal weight, one on each end. The farther kid "A" and closer kid "B" is to the fulcrum, the easier it will be for "A" to lift "B"

That being the case, you have to look at the changer and bellcrank differently

CHANGER:
FORCE = the changer finger
FULCRUM = the changer axle
LOAD = the resistance of the string on the changer head

So, the farther the pull rod is placed from the changer axle, the easier (and longer) is the force (or effort) needed to make the change. The opposite is true using a hole farther from the axle.

BELLCRANK

FORCE = pedal or lever
FULCRUM = crosshaft
LOAD = bellcrank (connected to changer & string)

The closer the bellcrank slot being used is to the crosshaft, the easier it is to be moved - the farther away, and the effort (or force) required is stiffer (but shorter)

[Lane Gray]

I appreciate how y'all explain the obvious stuff I overlook.
And it explains the problem I had rodding up that guitar