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the Rover
What are parabolic
springs?
(by TIConsole)
A parabolic
spring is basicly a leaf or a set of leaves which are tapered in a parabolical
way rather than a liniear. So from the middle, where it is thick, to
the ends , where it is thinner, the tapering steps down in a parabolical
manner i.e. Y = Xsquare + n where Y and X are related to the thickness
and the lenght of the leaf. (every 1 mm the leaf tapers by a parabolical
calculated value). The shape, camber, of the spring is not parabolical
but semi-eliptical. Parabolic tapered springs may not be confused with
linear tapered springs (every length step is tapered with the same value).
Although linear tapered springs can look the same they will not be as
good as the parabolicaly tapered springs. The reason why the parabolic
spring is more comfortable is simple. The multy leaf springs have interleaf
friction which makes them "bouncy" since it needs a cerain amount of
force to contra act the interleaf friction. Even if you grease the leaves
you will still have a multy leaf spring and it will never come close
to a parabolic spring since they still have interleaf friction which
is on the parabolic spring nearly nil. The tapering of the parabolic
spring handles the force distribution from the body to the axle. If
you make a multy leaf spring with only two leaves (non tapered) it will
break because it can not distribute the force correctly. The rate of
a parabolic spring is linear in contrast to the degresive rate of a
multy leaf spring. This means that the inward movement is similar to
the outward movement. The convetional multy leaf spring will need more
force on the inward then on the outward movement so this will result
in a highly uncomfortable ride.
The
differences and advantages
First of all, the parabolic tapering of the spring. This tapering is
in a parabolic way to asure maximum force deflexion and tranfer from
the ends to the middle section. This gives the best results in both
comfort and longlivety.*
Second, the number of leaves. The front springs have
only two leaves instead of nine or eleven. The rear springs have three
(load level B) or four (load level C & D) instead of ten or eleven leaves.
Third, the spring leaves do not rub against each other
over their entire length. Instead, the lower leaves are shaped at the
ends and 3 mm spacers are fitted between the leaves in the centre, thus
leaving a space along the length of the spring with friction only at
the ends.
*) Linear
tapered springs will not give this result instead they could be less
comfortable and possibly easier sprone to break.
The differences
and advantages
A much improved
combination of spring characteristics with the reduced thickness at
the ends of the springs provide improved comfort, wheres the strong
central part ensures a very goad load capacity.
Because the leaves are not rubbing together and the outer ends are serperated
by PU blocks, the problem of a build up of friction and rust is prevented.
Un-sprung weight is reduced because, for example, the front springs
weigh only about half as much as the standard type.
On
and Off road
The improved spring characteristics result in a more
comfortable ride on-road and off-road as well. The irregularities of
the road surface are better absorbed by the springs and there is good
control of the vehicle on corners. The typical LandRover feel of the
vehicle remains but the unpleasant bumps are gone. Off-road, the axle
articulation is very good, with some vehicles already being used for
trialling. Conclusion There is indeed a world of difference. The much
improved spring characteristic is a development which the Land Rover
owner has waited a long time for. This improvement is achieved with
no alteration to chassis or axles being necessary (as in coil spring
conversions). We recommend these parabolic springs to those owners who
want to use their LandRover as an everyday vehicle, on or off road,
and want to keep their vehicle leaf sprung. Whether you are doing a
full restoration or just dealing with the regular maintenance of your
Land Rover, these springs will enable you to enjoy your vehicle more.
We use them on our own Land Rovers - can we say more?
©
TIConsole
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