...the 'hint' is that you're looking at a BPP which has a Bigsby spring bracket on the end of the mainshaft, right??
The G lever is attached to the mainshaft, while the other two levers just 'freewheel' on it..the ball end of the G string is in front of the pivot point of the lever, so it lengthens the string by pressing down (against the tension of the mainshaft return spring)...
FWIW, I use a similar method on my 6-lever version, except I have two (opposing) springs at each end of the mainshaft...mine can rotate in either direction to either raise or lower the pitch of the two strings attached to it..
..the other four strings having their own individual levers, free-running on the same mainshaft, ala Don Balde..
I use 'collar bushes' (similar to those used by Dan on other variations of the Dobro theme) to attach those two strings to the mainshaft, which has the effect of increasing the diameter of the shaft at that point, allowing more pitch variation for a small amount of shaft rotation.
Yes...I spent about two years designing and building the thing... MUCH modification of the standard BPP components, and a lot of new fabrication of additional components... Glad I did it, but not sure I want to build too many more..
HTH... ask more questions if you need to... either Jerry or myself seem to have explored just about everything you can do with these things except crack walnuts..
Cheers from Oz...where we're heading into what you call Fall...