The Series 1,2 and 3 Land Rovers were fitted with standard leaf springs at production. The leaves of these springs are of equal thickness throughout their length and are in contact with each other throughout their length.
When a Series Land Rover rides over an obstacle, the leaves flex and also rub against each other, causing friction. The more friction there is, due to rust etc., the more bumpy the ride in the Land Rover becomes. Hence the need for lubrication.
are thinner at the ends and are tapered in the curve of a parabola. The parabolic shape is better able to distribute stress more evenly than one of uniform thickness. The centre of the leaf can then be thinner and also less leaves are needed for equivalent strength. A parabolic springs setup for a Series Land Rover would range from 2 to 4 leaves, depending upon load requirements, whereas the standard leaf setup would vary from 9 to 11 leaves.
The parabolic leaves do not touch each other except at the ends and in the middle. There is less friction, resulting in a smoother ride in the Land Rover.
Because parabolic springs distribute stress more evenly, they put less stress on the chassis mounting points. The springs are also lighter in weight and so respond more rapidly to changes in ground conditions.
There is an approximately 40% reduction in weight compared to standard springs. So a Land Rover sporting parabolic springs gains a small advantage in fuel economy over the long term.
less leaves makes for greater ease of movement and this leads to about 15% increase in wheel articulation. This in turn means that standard shock absorbers are not upto the job as their extension travel is too limited.
For a detailed photographic account of fitting parabolic springs to a Series III Land Rover see James Ferguson's article on his website via the Land Rover tech articles section.
There are undoubted advantages to fitting parabolic springs. Next month's homepage will focus upon some of the situations where they pose more of a problem.
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