A huge, gray machine rumbled softly, yet with undeniable strength and power.

This massive machine rumbles across Martian terrain, searching for energy crystals.

The machine rumbled relentlessly forward and rose up to the top of the pile, almost somersaulted over backward.

When the massively powerful machine had started up and rumbled across the field, he felt both wonderful and afraid.

A tracked machine rumbled and puffed in the background.

The machine rumbled to life and there was a hiss.

The machines on which they rode rumbled like thunder.

The machine rumbled, and then Tally felt it lift from the ground.

By now, the huge machine was rumbling and the gas-venting was continuous.

The moving way takes me down to another level where yet more machines rumble.