Parabolic leaf springs

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Originally Posted by Lotz-A-Landies

I think that is outstanding articulation on leaf springs - why would you go to the trouble of re-engineering a series vehicle with coils when parabolics can do that.

Note to self: Must put pennies in piggy bank for new RMP's

Diana

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Thanks Diana, however those aren NOT RMPs. They are custom Semi-Elliptics that I built myself. I have never seen a parabolic-equipped vehicle which gets comparable travel (apart from one guy in the UK who uses whacky-shackles and rotating spring hangers).

Parabolics are actually surprisingly stiff in terms of spring rate. What makes them comfortable is the lack of interleaf friction. This means that a parabolic spring behaves like a coil over short amounts of deflection/travel (i.e. can move rapidly to soak up bumps). However, for serious wheel travel, a parabolic is inhibited by the thickness of the leaves, as the stress between the face of the leaf which is in compression and the face in extension is much greater for a thicker leaf than a thin one.

Btw - parabolics are correctly termed "single leaf springs" - or at least they are in engineering design manuals. This is because each spring is unaffected by the others in the pack. They are also still semi-elliptic in curvature, the taper in the leaf is the only parabola.

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Originally Posted by Bisho

so how much is a lot troy? or is that classified information! if only the mrs knew eh.

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John,

Sorry that it has taken me a long time to get back to you. My Rocky Mountian setup cost $1800. And yes - the missus did spew when she found out. :D

"...If you have these springs just cut a taper in the leaves, smooth up the edges and that is all. I didn't have these so I bought after market SWB petrol spings that have 9x5mm leaves so the rate is 315lb/in!!! - I removed 3 leaves (so now 6), tapered and smoothed the edges and had them reset ..."

Isuzurover,
Please excuse my ignorance, but what do you mean by "taper" the springs? (Is this cutting them to length so that they taper down evenly from the longest leaf, or something else???)

Thanks

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Originally Posted by cjc_td5

"...If you have these springs just cut a taper in the leaves, smooth up the edges and that is all. I didn't have these so I bought after market SWB petrol spings that have 9x5mm leaves so the rate is 315lb/in!!! - I removed 3 leaves (so now 6), tapered and smoothed the edges and had them reset ..."

Isuzurover,
Please excuse my ignorance, but what do you mean by "taper" the springs? (Is this cutting them to length so that they taper down evenly from the longest leaf, or something else???)

Thanks

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Hi Chris,

Not exactly - Another word would be chamfer. Spring leaves with square cut ends (a-la standard landie) have a higher "stiffness factor" (engineer speak) than those with tapered chamfered ends (the corners chopped off diagonally). Hope that makes sense? Basically you want to make it so the ends of the leaves will slide forwards and backwards smoothly.

e.g. see here: The leaf closest to the main leaf is chamfered/tapered, the next one isn't.
https://www.aulro.com/afvb/images/im...008/03/461.jpg

I have dug out some pics of my setup for anyone who is interested. NOTE - I hadn't yet cham,fered/tapered the leaves in these pics.

Front compressed (not yet full travel - compresses bump stop about 1.5" on fill travel) - note this is a military chassis with the bump stop spacer removed (rear still in place).
https://www.aulro.com/afvb/

Rear Springs - yes the inner clamps are ridiculously long - I shortened them later
https://www.aulro.com/afvb/

One new rear and one old rear fitted:
https://www.aulro.com/afvb/

Rear compressed (also not all the way):
https://www.aulro.com/afvb/

This is useful information. I'm about to embark on a suspn project. I'd prefer to keep the bog standard leafers for budget reasons. I think one leaf has been taken out of each of the rears by the previous owner and it's a but saggy. If I can find a torch I'll go out and count 'em. I'd like to get the rears reset without adding leafs. I suspect the front is untouched. It is as stiff as a board. Can I remove leafs from front? I need new shockers too. What sort should I go for ... ??

Glad the info was helpful.

First thing is to measure EXACTLY what you have (number of leaves and thickness), and check condition (good / rusty and spreading, etc.).

If you have genuine springs, the leaf counts and thicknesses should be the same as here:

https://www.aulro.com/afvb/images/im...015/01/984.jpg
(thanks Diana)

There is no reason you can't get the springs reset (AND tempered) without adding leaves. You can also pull leaves out if you have a very light landie or aftermarket (thicker) springs.

Reading all of this has made me excited about my new purchase...
Need to see What DaveS3 did to the Stage1 in the springs....

This does indeed look really good!!! What forums are all about!!! isuzurover... that is fantastic information you are sharing there and I am seriously considering doing the tapering of the leaves as you suggested. They are aftermarket leaves though... I might see if I can borrow that leaf spring design manual from somewhere as I have an engineering background and see what I can come up with!

I've got a Ti-console set on my stage one and recently fitted a set of Rocky-Mountain ones to a Series II SWB and both work well, correct shocks are vital, I had the pro-comp set that came in the rocky-mountain kit on the stage one and they worked better than the ome ones on it before but now I've got rancho adjustables and you can get some amazing smoothness as long as you adjust to suit the load.

With the pro-comp and probably rancho shocks you need to regularly check that the boots are draining. I had to replace mine cause the boots were holding water and rusted the shock around the seal, letting the gas out!!

Andrew