F ocus on SUCCESSFUL INVENTIONS
Words Terry Owen
Caravan chassis and running gear - part 2 In this second instalment of chassis inventions that changed our world we look at auto reversing overrun brakes, semi-trailing arm axles, hitch head stabilisers and active stabilising devices
Auto reversing overrun brakes
L
ong after the operation of the overrun brake was perfected its main drawback was that it would often apply the brakes when reversing, especially over rough ground or uphill. I well remember my first caravan in 1974. If you wanted to reverse you first had to make sure the hitch mechanism was not in compression, then you could move over a lever that prevented it going into compression so the brakes would not operate when you reversed. I seem to remember it automaticalThe way it used to be
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ly disengaged when you went forwards again. However, if you were executing a multi-point turn because you’d taken the wrong road, it was a nightmare! A better solution was needed and it came a few years later with the invention of the auto reversing overrun brake. A German patent DE3203113A1 from 1981 describes ‘… two positively coupled, floating but limited tangential to the wheel axis movable brake shoes, thus preventing tensioning against the brake drum when reversing…’. The patent was assigned to Olbernhau Fahrzeug (Olbernhau Vehicle), although Knott GmbH claims to have invented it and manufactures such brakes to this day. Like many of the best inventions the auto reverse overrun brake is simple but ingenious. AL-KO’s version is discussed here.