lighter car leaf springs
lighter car leaf springs
(OP)
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: superior spring (leaf spring) materials to 17-7 ch900 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
thread404-321076: superior spring (leaf spring) materials to 17-7 ch900 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





RE: lighter car leaf springs
Quando Omni Flunkus Moritati
RE: lighter car leaf springs
I'm not a car designer. But I would expect them to look at composites or else change leaf springs to something other than leaf springs if they wanted to really save weight on that item.
RE: lighter car leaf springs
Like most other things, spring design is complex enough that it's not really possible to make a blanket statement about any one material being superior to all others, because there are so many variable other than material involved in any particular application.
Mike Halloran
Pembroke Pines, FL, USA
RE: lighter car leaf springs
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: lighter car leaf springs
Some Studebaker owners report that using flex-a-form springs save a whopping 70-90 lbs (at the end of the car that already is too light).
50 vs 8 lbs each. 2 required. Cost supposedly not much more than steel.
http://www.flex-form.com/products.asp
Life generically proven in Corvettes at both ends since 1984 (optionally since 1980?). Supposedly no Corvette composite spring has been replaced due to fatige failure.
RE: lighter car leaf springs
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: lighter car leaf springs
Beryllium copper is a nifty material for springs because it has the yield stress of spring steel, and the elastic modulus of bronze. This means you can bend it more. This is a useful quality in optical fixtures, and on electrical connector contacts.
Beryllium copper is mostly copper, so I would expect it to be heavier than steel. I would wonder about the fatigue qualities of any non-ferrous material, although car springs may be loaded sufficiently that this does not matter.
--
JHG
RE: lighter car leaf springs
The SAE leaf spring handbook is an invaluable resource even now, since it explains the many subtleties.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: lighter car leaf springs
Regards,
Terry
RE: lighter car leaf springs
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: lighter car leaf springs
Obviously, every leaf spring material has certain benefits and limitations. One benefit of both BeCu and Ti is that they have natural corrosion resistance. Or from an aesthetics standpoint, just imagine how beautiful a polished BeCu leaf spring would look.
RE: lighter car leaf springs
I suspect with copper or titanium springs, you'd start having cases where people came out of the Walmart only to find their springs had been stolen.
RE: lighter car leaf springs
Actually, what you said is sad but true. I live in southern California, and a few months back a co-worker of mine had the catalytic converter stolen from his Toyota 4Runner during broad daylight while it was sitting in the company parking lot. A used catalytic converter is worth far less than a pair of BeCu or Ti leaf springs!
RE: lighter car leaf springs
RE: lighter car leaf springs
Received a quote for fibre glass leaf springs, from mark@flex-form.com
Here is the data sent to him:
http://classic-carshow.com/cars/Vauxhall/Cresta/PC...
dry weight: 2796lb/1.248ton (1268kg)
Mark must think fibre glass has enough load bearing and tensile strength.
RE: lighter car leaf springs
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: lighter car leaf springs
I still wonder what vehicle the original poster wants to retrofit. It can't be a late model car; beam axles and leaf springs went out of favor in the 1970's. Pickup trucks still use them, but among all the places to save weight in a pickup truck there must be 100 places more advantageous and less safety-critical than this one. If it's for a vintage car, using anything but steel leaf springs isn't period-correct for an original restoration and if it is for a resto-mod, the path to better handling characteristics usually involves replacing the beam-axle and leaf-spring arrangement with something completely different and using coil springs. Substituting composite leaf springs for a Hotchkiss axle won't make that suspension arrangement's other faults magically go away.
RE: lighter car leaf springs
This is vastly different to a one-off job, where the choice, crudely, is between a fragile product and a heavy one.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: lighter car leaf springs
GregLocock:
"serves no function in guiding the path of the wheels as the suspension moves"
Noted, thankyou. Will contact Flex-com about the sideways load / stress on the springs.
BrianPetersen:
"what vehicle"
http://classic-carshow.com/cars/Vauxhall/Cresta/PC...
"there must be 100 places more advantageous and less safety-critical than this one"
the idea is to save weight on everything possible. Things considered are fibre glass body panels, alloy wheels, plastic petrol tank. Being true to the period with unseen parts is not relevant as the body will be unmodified.
RE: lighter car leaf 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.
RE: lighter car leaf springs
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.
RE: lighter car leaf springs
"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.
RE: lighter car leaf springs