Talk:Corvette leaf spring/Archives/2018/December

Disadvantages?

I read this article and come away feeling like the FRP leaf spring is some sort of suspension panacea, which defeats steel leafs and coils in almost every way from being lighter, to giving better ride, to lasting longer, etc. If this is true, then why is the Corvette one of the very few automobiles to use it? There are obviously good reasons NOT to use them, but this says nothing about it. Sure it mentions "cost and packaging issues", but if cost and packaging issues were the only problems with FRP leaf springs, they'd use them on Ferraris and Lamborghinis, etc, since they appear to be so clearly superior to steel springs in every category. The fact that Lamborghini ISN'T jumping all over them even while they are spending millions to shave a few pounds from the chassis, suspension and brakes, suggests that there are other good reasons they don't use them. I'm not saying that there is anything wrong with FRP leaf springs, only that there MUST be disadvantages not mentioned, or barely touched on here, or the automotive world would be all over them. And I can't quite bring myself to believe that it's merely that "the automotive world is too conservative and resistant to change, and the market doesn't always tell you when an idea is good or not". They TRIED them, but for some reason they decided not to go any further. Even the Corvette stopped using them as of a few years ago, IIRC...they went to using steel springs instead. This at the same time as they increased the price and the performance of the car drastically; if FRP springs had such enormous advantages over coils in all categories, it seems they would stick with them, especially since they angered Corvette purists more by abandoning them than they would have had if they had kept them. My guess is that packaging is the biggest concern, but that doesn't seem to explain everything. In a FR Corvette having a transverse spring means that it has to pass directly under the engine oil pan, which means the engine must sit at least an inch higher than it would otherwise...and this is a amount in a performance car. That wouldn't make sense for the new RMR Corvette, except for the rear axle. But for other cars it would maybe require modified oil pans, which cost extra, or theyd have to figure out a way to route it so it doesn't interfere with the engine or diff. This is all pure speculation, but this is important stuff, this ought to be in the article, not just a sentence about "packaging issues in race cars". What is described here sounds too good to be true, and there is no obvious explanation for why it's not universal or widely used.

70.109.164.53 (talk) 06:20, 19 November 2018 (UTC)

This article fails on nearly every level. Yes, your first observation is right - composites made leaf springs once again a practical means of providing suspension, where a steel leaf had been obsolete for decades. This has little to do with Corvettes, yet this article still heavily implies this inappropriate connection. Andy Dingley (talk) 11:49, 19 November 2018 (UTC)

The IP editor raises some valid points but others are incorrect and most is speculative. I sympathize with much of the speculation, especially the why don't more use it. So first, the error, the Corvette still uses the composite leaf springs front and rear. It appears the mid-engine C8 will use coils but we don't know if the future front engine Corvette will use coils (I'm assuming the C8 will effectively be split into two platforms per rumors I've read). So the conclusion that moving from leaves to coils improved the car's performance is wrong since it currently hasn't happened.

Speculation on my part, I suspect cost vs performance (handling, weight, life cycle etc) is the primary reason few companies use the technology. The cost isn't trivial as it involves much higher tooling costs vs a coil spring. The coil winding machine can turn out Ferrari coils in the morning and Corolla coils in the afternoon with basically just a software change. The leaf is wound on a form then molded. That means you have to buy the mold for each spring. For high volume cars the unit cost is a problem. For low volume cars the tooling costs are high thus driving up the unit cost due to tooling amortization. The benefits are there but not huge. Fatigue life may be better than coils but unlike the 1970s I don't see many cars with sagging springs anymore (other than leaking air springs). Also, longevity can be compromised by chemical exposure. The handling benefits are mostly due to weight savings. However, for the same cost to the mfr other weight savings such as lighter wheels, uprights etc may be an option. Designing a car is a series of trade offs including in cost so if you want to save weight other options may be more cost effective. This is all stuff I would add to the article if I could find a RS to support it. And that speaks to the issue here. This is a topic with limited sourcing options.

I don't agree with Andy's claim that this article fails on nearly every level. In fact in many regards I think it's quite good. However, I agree that the naming is problematic. This was an issue discussed a while back. The suspension design isn't limited to the Corvette (Volvo is currently using the same concept) but what is a good name that keeps the scope here? Springee (talk) 13:49, 19 November 2018 (UTC)

Sorry, I have an account, but I keep forgetting the password. I have to go and find it so I can sign in again. Anyway, you needn't convince me, I'm just saying that this is what the article left me wondering. My point is that it ought to mention this stuff in the article, not just describe what wonderful things traverse FRP springs are. And what about longitudinal FRP springs? You can buy them to replace stock leaf springs on pickups or cars, don't know if any manufacturers are using them at all. But surely the subject is related; is the main point of this article that the springs are FRP, or that they are transverse? If it's because they are FRP, the only difference is method of installation, and if it's the fact that they are transverse, they are nothing new, and are related to wagon springs and Model Ts. Even if it's both, they are still related subjects on both sides.

64.223.120.131 (talk) 06:15, 1 December 2018 (UTC)

I think one of the hardest things about writing on a subject like this is finding reliable sources. Much of what I know about the subject comes from things like my own personal experience (a professional background that helps understand the subject), direct conversations with people who do this sort of thing for a living, reading forum topics related to suspension setup, magazines that aren't easy to find on line etc. I've tried searching the academic literature but it's rather sparse as suspension design, outside of computer control, doesn't get much academic press these days. I would like to have a more detailed discussion of the material but without a RS from which to source it I'm not sure what to do.

I also understand your comment about what is the subject. If you look at the archive that discussion has come up before. The problem here is we actually have a few features that combine to make something rather novel but individually none are that novel. The fiberglass spring is one. They are actually used as heavy truck springs instead of traditional steel springs. GM used such springs on some versions of the Chevy Astro van. In that application vs a traditional leaf spring the fiberglass spring benefits from no internal stiction, is lighter and has a greater cycle life. I'm assuming GM decided they weren't worth the cost since they stopped using them I think in the late 80s or early 90s. In terms of suspension geometry and fundamentals that application is basically just another leaf sprung Hotchkiss setup.

So what about this being a transverse spring setup? Some people said this should go in the transverse leaf spring suspension article(s). Well the one about Transverse leaf spring front suspension doesn't really apply since that describes the Model T Ford's beam axle located with two links and leaf spring acting as support and lateral links. That is really a subtype of a beam axle vs the Corvette which is clearly an independent type. So it doesn't really fit there. We also have Transverse leaf spring which is a bit of an odd bucket located in the independent suspension article. The fact is there are a number of independent suspension types that use individual left and right leaf springs (even if the left and right sides are part of a single spring assembly). But many use the spring as a control link and almost none use the "S" bending of the spring as a type of anti-roll bar. Fiat did (and I suspect that is where GM got at least that part of the design for the Corvette). So then we have the unique combination of independent suspension linkage, a leaf spring that is not part of the suspension geometry and is flexible enough to allow the two point mounting that makes the anti-roll effect possible. Since Volvo has used it on a number of previous and current models and GM used it on several cars other than the Corvette I agree that "Corvette Leaf Spring" ignores other applications. At the same time I suspect only the Corvette's use of such a spring has caused such controversy/interest in the auto enthusiast world. As I said a while back, I'm open to a new name or new location but I cant come up with a suitable name or location so I haven't pushed for a change. Springee (talk) 01:42, 2 December 2018 (UTC)