Moment of Inertia and Centre of Gravity

/Moment of Inertia and Centre of Gravity
Moment of Inertia and Centre of Gravity2019-02-07T16:13:57+00:00

A unique facility to measure the Moment of Inertia & Centre of Gravity

If an engineer was faced with the issue of obtaining the centre of gravity of a road vehicle, an easy option would be to check a 3D CAD model and an answer would be forthcoming. The centre of gravity would be obtained very quickly, probably referenced to the co-ordinate system of the vehicle. There would also be further data giving the moments of inertia tensor and the principal axes. However, the figures quoted would have been obtained from the computer model which may have been more suited for crash modelling and the accuracy of certain components may have been compromised. As the moments of inertia of a vehicle are made up of the sum of all the individual parts own local inertia multiplied by the distance squared. Any component located the furthest distance from the centre of gravity needs to be modelled accurately

3-Axis Moment of Inertia Facilities

Mass Range: 1kg – 2600kg
Dimension Range: 6.5 (L) x 2.8 (W) x 2 (H) m max

Centre of Gravity in 3 Axis

Momments of Inertia Pitch, Roll and Yaw, Principal Inertias

Please note that the rig can also be used for other automotive objects such as engines, gearboxes, seats, aircraft components, missiles and sports equipment.

Important effects on the dynamics of a vehiclecomponent or system

An alternative method of obtaining the moments of inertia for a full vehicle is to perform a test in a laboratory. Cranfield Impact Centre can provide that service with their unique air bearing based facility at Cranfield, UK. It has been in operation for over 30 years with a wide variety of vehicles been tested such as Formula 1/ sports cars/road and prototype vehicles. The vehicle is supported on an air bearing and allowed to oscillate in defined orientations against the resistance of springs. The time period of oscillation is measured and the inertia is subsequently calculated. The centre of gravity can also be measured in three directions by inclining the vehicle over a few degrees and measurements taken with a load cell.