Abstract: A protective device for an inertia wheel rotating about an axis and mounted inside an enclosure comprising at least two anchoring frames, wherein the said device comprises a cowling of generally semicylindrical form whose axis is parallel to that of the said wheel and which surrounds the latter and a horizontal arm the first end of which is rigidly fixed near the top of the said cowling and at least three shock absorber sets, one of the said sets being fixed between the second end of the said arm and one of the said frames and operating in a horizontal direction, two other sets being fixed between the lower edges of the said cowling and another frame, while each shock absorber set may operate in both directions.