East Broad Top - Southern Valve Gear

Viscerally, I have had difficulty seeing how a Southern Valve Gear works. The two hanging levers somehow make the backside of the bell crank go up and down vs. down and up, depending on where the top of the one hanging lever is on the stationary link. I get that the bell crank translates the up and down to back and forth on the valve stem. Also, there is no combination lever to give the valve stem a lead. I know it all somehow works. But, it still baffles me how those two hanging levers make the backside of the bell crank correctly go up and down vs. down and up. And, how this can also create a valve stem lead without a combination lever.

Robert





p.s. - it would be nice if the White Pass & Yukon could grab one of these locos, and get it to run again.