A clockwork interlock was simply physical logic enforced through solid steel.
In the machine shop bay next-door to Switch-Point Number Four, Giles Croft stood before a heavy workbench assembled from scrap oak ties.
Spread across the bench were five heavy helical steel coil springs, two sliding cast-iron slide-chairs. A set of forged steel tappet bars etched with care locking notches.
Beside the bench, Master Borin Bronze-Lung wiped a heavy grease rag across his copper-braided beard. His measuring tongs measured the width of a newly hardened coil spring.
“Silicon-hard dark metal spring steel,” Borin announced, tapping the spring against the iron vise.
“Oil-cooled and hardened at four hundred degrees. You can compress this coil under ten tons of dynamic axle load, Croft. It rebounds to within half a tiny fraction of an inch of resting length.”
Giles adjusted his glasses, pointing to the sliding sleeve linkage in his clockwork sketch.
“The deepest error in the old switch was rigid coupling,” Giles explained.
