Assertion: engine's imbalance | /r/Causes | up-and-down vibration
Facets:
value: at twice crankshaft speed
type: MANNER
Source sentences:
text: As a result, two pistons are always accelerating faster in one direction, while the other two are accelerating more slowly in the other direction, which leads to a secondary dynamic imbalance that causes an up-and-down vibration at twice crankshaft speed.