Hi Albert -
It all becomes clear once you have both in your hands, but I realize that is difficult or impossible given your current situation.
the rear set trigger is pulled, which loads the larger leaf spring to the rear, until the nose of its knife slides by and under the "engagement point" of the front triggers blade assembly. You can see in the above that it's a very small engagement point.
In this position, the blade of the rear trigger is held down by that wee little engagement point, and the rear trigger spring is loaded for business.
So now a very light pressure on the front firing trigger trips the engagement & releases the rear trigger blade, and - since it's spring is loaded - it snaps up throughout it's range of motion.
Except, of course, on its way up, it will hit the sear bar of the lock (red dot above), which disengages the sear from the tumbler, and fires the lock etc etc.
So what do you need to worry about when putting these parts together in a build ? probably more than I'm aware of - but somewhere near the top in importance is the positioning of your trigger assembly (fore and aft aspect) with respect to the sear. Obviously the rear blade has to hit the sear bar.
I had an assembly where I messed up and the blade just slid by (behind) and jammed on the sear bar - fixed that by soldering on a hardened bar to add length to the knife.
also need to worry about the relation between the sear bar and trigger blade in the unset postion (controlled by the depth of your trigger assembly - but can also be adjusted by modifying the height of your trigger blade.
Don't want your rear trigger blade bearing on your sear bar in the unset position. dangerous.
(
so in the "unset" pic above, there really should be a small space between the red dot and the rear trigger blade!!!)In older pic below, you can just see the trigger blades in the sear bar hole in the lock inlet. Obviously you need to have a pretty good idea exactly where your sear bar is when you start to position your trigger assembly.
You will note in Rolf's trigger thread that Jim K. says that the angle of the blade in relation to the sear bar doesn't really matter, the energy in the spring should trip the sear. If it doesn't, one checks for wood interference, binding, and correct spring tension.
Others with more more experience probably have more to add (and they already did since I started writing this!).
In short, once you get back to the good ol' U.S. of A and get both parts in your hand, it becomes pretty clear how it all works.
be safe,
mike m
