The throttle operating rod and stuffing box is what allows the engineer to control how much power is applied to 1385’s driving wheels. The throttle rod reaches through the stuffing box mounted on the backhead to the bottom pin hole of the bellcrank mounted on the throttle body. When the engineer pulls out on the throttle rod the bellcrank turns that motion 90 degrees, pushes up on the spool in the throttle body and opens the steam passage to allow the superheaters to fill and supply the cylinders.
In order to keep the steam in the boiler from leaking into the cab the stuffing box and packing gland are made up of three pieces – the stuffing box, the bronze donut and the packing gland. The stuffing box and donut must seal against the flange in the backhead of the boiler. The cone shape cut into the end of the packing gland must squeeze a relatively soft packing material tightly enough around the throttle rod and into the stuffing box base to keep steam from leaking past.
Here is a picture of the old and new operating rods. The old rod had been roughened by rust which would make it impossible to keep the packing around the rod sealed. Lastly, here is a look at how the throttle rod extends through the packing gland and stuffing box reaching for the throttle bellcrank.