lighter car leaf springs 2

[plutogamer]

To replace the leaf springs on a car, to reduce the overall mass. Would beryllium copper be strong enough, manage the same loads and stresses as steel, be similar mass to titanium and cheaper than titanium?
thread404-321076 gave some information (below) but not all the answers.
titanium … yield stress equivalent to spring steel, lower elastic modulus, lower stress, can be deflected more than steel.
beryllium copper … yield stress and elastic modulus similar to titanium, cheaper and more available, more corrosive than titanium.
Delrin?
Thanks

 

[Tmoose]

"Will contact Flex-com about the sideways load / stress on the springs."

If this quest for light weight is driven by racin' , then a panhard bar would not spend the entire 70 lb weight loss, if its side loading was not objectionable.

 

[BrianPetersen]

A panhard rod would be capable of better side-to-side axle location and remove the obligation of absorbing side loads from the leaf springs ... but if you do that, make sure the panhard and the leaf springs aren't both trying to do that job differently, thus binding up against each other. The panhard should be as long as possible, as horizontal as possible at nominal ride height, and with its pivots at the same height as the leaf springs, and it might be advisable to arrange for some sideways compliance (intentional sideways clearance, soft bushings, etc) in the way the leaf springs attach at the pivots at both ends. This way the leaf springs don't have to take up side load. They'll still have to absorb axle-wrap loading from accelerating and braking, and fore/aft locating-the-axle load between the axle and the fixed pivot.

One thing to be mindful of is that conventional leaf springs are built with multiple thin leaves partly because this causes the leaves to rub against each other a bit when the axle moves around, which adds some (frictional) damping to the system in a direction that the normal hydraulic dampers can't fully absorb. This helps dampen out oscillatory axle-wrap, which would otherwise lead to all sorts of axle-hop and other bad stuff. I don't know if composite springs would be able to be constructed in that manner and survive. (It also adds to the rough ride that conventional leaf springs are notorious for, but that's another matter.)

All of those loads can also be taken up by linkages, and with less axle-wrap and deflection than leaf-spring setups have, so that if you get the geometry right, the axle-wrap doesn't happen in the first place. And by the time you're done all that, you might as well do ALL of the axle locating with a linkage, and toss the leaf springs in the trash and put in a set of coil-over shocks!

The Corvette independent setup doesn't have any of these issues since the wheel spindles are fully located by the linkage, the hydraulic damper is responsible for all the damping, and the spring only has to be a spring in one direction of movement.

 

[Tmoose]

Stephen (Mechanical) wrote -
"I've seen lots of sheet metal rust out on cars and trucks, but never have seen leaf springs that rusted out. So that's pretty much a cosmetic problem."

A broken spring, whether leaf or coil, almost certainly will show the crack initiated from a badly rusted area.

Up here in Massachusetts the roads are salted pretty aggressively in the winter. Modern car bodies suffer somewhat less than in the old days, probably because there are warrantees requiring no perforation for X miles and Y years.
GM says this "All body and sheet metal components are warranted against rust-through corrosion for a minimum of 6 years/100,000 miles (whichever comes first). "

I think it is significant there is no mention of suspension parts or brake lines or even frames. This is confirmed by A peek under late model US trucks around here that sometimes reveals the body is going to outlast the rust ravaged nether regions. A rusted leaf (or coil) spring is far more vulnerable to fatigue cracks.

 

[pmrobert]

RE leaf springs not rusting to the failure point: There are a lot of owners of boat trailers in salt water service who would disagree with that premise. Even well rinsed after use you are lucky to get much past 3 or 4 years.