[Manamendra]

Could somebody explain exactly what "parabolic springs" means as I see heaps of ads in LRO International all the time. I was under the impression that all leaf springs were parabolic but obviously I seem to be wrong :confused

 

[Bogatyr]

Manamendra,
Yeah, most modern leaf springs are parabolic, so this isn't much new. However, series trucks came with elliptical (IIRC) springs, just a different bend to them. You can also usually tell the difference by the number of leaves in the spring pack. Ellipticals will have what, 9-11 leaves on our trucks, while the parabolics won't have more than 3...

Bogatyr

 

[TerryS]

Hopefully, someone younger than myself will remember the formulas which defines a parabola and an elipse, but that's too far back for me. What I do know about parabolic springs is that it is their construction that makes them different than old fashioned leaf springs. You can see that the center is the thickest cross sectional area and they become progressively thiner towards the ends, so their first reactions are at the ends and increases in deflection are resisted by increases in section thickness. I think the X-Y plot of force and deflection is parabolic, not the shape of the spring.
Old fashioned leaf springs were made up of pieces of flat, equal thickness sections of high carbon steel. The more resistance to force they needed, the more leaves they used in their construction. Both types are progressive in delections but the old leaf springs are very stepped in their progression and parabolics are very smooth, because they are a single homogeneous piece of metal

As far back as the late 70s, Ford used Parabolic leaf springs in their pickup trucks.

 

[Manamendra]

I'm a wiser man this morning. Thanks guys!!