Large jaw type rock crushers are very common in the stone and gravel business. They are generally portable and can be towed by tractor trucks. The jaw crusher creates a pinch point that fractures larger rocks and reduces them to about the size of your fist. They are further crushed in a cone crusher and reduced to gravel as small as 1/4 inch.
The jaw crusher has two large flywheels powered by a diesel engine that spins an eccentric which causes a crush plate to oscillate making a pinch point fracturing rocks. The flywheels are indexable and have bolt-on plates to adjust the counterweight size to compensate for wear.
From a balancing standpoint, the crusher acts very much like a one cylinder engine. The counterweights in the flywheels act exactly as the counterweights in a crankshaft. The theory for adjusting the counterweights is identical.
Single cylinder engines are balanced to 50%. That means a bob weight is placed on the crankshaft that represents 50% of reciprocating weight, added to 100% of rotating weight. Reciprocating weight is 50% of, one piston and wrist pin and top of connecting rod, added to 100% the bottom of the connecting rod That weight is clamped to the crankshaft journal. The crankshaft is now balanced with the flywheels and the counterweights are adjusted for phase and amount.