The above diagram shows the detail of the over run brake actuating mechanism of the pre 1960 caravan shown below.

2 = the hand brake (but the ratchet is not shown).

3=  the hand brake pivot.

4= the rod leading to the brakes.

5 = the telescopic housing.

6 = telescopic arm.

7  = the housing which fits over the tow car tow ball.

8 =  release handle for above housing.

9 = washer.

10 = spring to absorb shock of trailer running into tow car.

11 = collar

In the 1960’s  the mechanism was clearly visible but although on the latest caravans  in the class 750kg to 3500kg the mechanism has been covered up the essential details have remained unchanged, except that a hydraulic damper has replaced the spring.

see

www.20six.co.uk/roadtrafficaccidents

para 10ci

for further details of the case against over run brakes.