# Automotive How to calculate body roll on a car as a torque?

1. Apr 29, 2014

### Webbd050

When a car turns there is a centripetal force acting at the tyres to get it round the bend. There is also an acceleration of the chassis away from the bend acting at the centre of gravity. These combine to create a torque which causes the chassis to roll about the roll centre. Is this correct? Ive calculated this torque as 1292Nm which seems very large to me. What would a typical value be? Thanks

2. Apr 29, 2014

### jambaugh

Let's see... a car can mass on the order of a metric ton =1000kg assume a 1/10th g acceleration is typical for centripetal acceleration say 1m/s/s so 1000 newtons is not unheard of as the centripetal force. Then assume COM and tires are on order of 1 meter apart and you get a 1000Nm torque about COM (or tires or roll center since centripetal force and tire force act as a couple.)

Your number seems reasonable to me.

Traveling 36km/h = .6 km/min = 10m/sec and making a 10 meter radius circle you'd have an acceleration of 100/10 = 10 m/s/s or about 1 "gee" and 10 time my calculated torque. We can agree that a turn requiring a 45deg bank probably would threaten to roll the car if on the flat (assuming it's traction held otherwise).

3. Apr 29, 2014

### Webbd050

Thanks thats great :)