Overturning Moment
The overturning moment is the stress that arises from the lateral force multiplied by the height of the centre of gravity and tries to tip the vehicle over. The quantity that resists it is the weight multiplied by the half-width between the support points. On tall and narrow vehicles the margin is smaller.
A simple balance is set up: the tipping effect is roughly lateral force × centre of gravity height, and the resistance is weight × support half-width. As the resistance gets smaller or the tipping effect gets larger, the safety margin shrinks.
- Sources of lateral force: crosswind, sloping ground, a push applied from one side, an open awning.
- Height: putting heavy items in the upper lockers raises the centre and directly lowers the margin.
- Width: spreading the support points outwards increases the resistance; that is why the jacks are placed as far outboard as possible.
The measures to take while parked are clear: place the vehicle on ground as level and firm as possible, distribute the load low down and evenly, retract the awning in strong wind, use the wheel chocks. To the extent that the levelling system holds the vehicle level, it keeps the weight vector close to the middle of the support area; but on its own it is not a safety device against overturning.
Context in which this term is used: RV automatic levelling guide