Okay, So I've been steadily plugging away on the '63 nova longroof I picked up from glendale a month or so ago. I've got it mostly sorted out and running well, so now I'm looking down the road as to what I want to do to the car. I was looking at different air ride options that I can pursue and stumbled upon the fatman "wonderbar" rear setup that basically seems like a pair of cut leafsprings that locate the axle in a two link fashion with a panhard bar for lateral location. I like the idea but I'm curious as to what others think. Seems like something you could fashion pretty easily at home rather than buying a kit. The primary things that concern me about it is: would I be able to use a stock leaf spring or would it want to wrap too much under acceleration and decelleration? secondly, on some of the fatman kits they have the coilover mounted infront of the axle, while on other kits it's located behind the axle. obviously since I want to run bags I'd probably mount them to the axle tubes, but I see how if you mounted them behind you'd get quite a bit of rear end load under acceleration, whereas if you mounted them in front it would be the same thing but under braking/decel. Any ideas which is better, or if this is a ****tastic idea all around? Here's a pic of the kit for a camaro so you get the idea, the camaro mounts the spring/shock behind the axle, whereas the nova mounts it in front of the axle I believe.
I'm not sure you understand all the physics at work in a suspension system. The placement of the load bearing spring forward or aft of the axle tube will make no difference in a 2 link where the links are rigid at the axle. You don't want to use cut springs because they aren't as straight as flat stock or tubes. You'd wind up guessing about pinion angle and they may have some unwated flex in them. You could easily rip-off this design using tubing instead of the old springs. Bags can mount ahead, behind or on top of the axle, so long as the mount is properly designed. This is a decent design, but it is full of compromises. I would decide on the primary use of the car and then design a suspension best suited for that use. There isn't much wrong with the stock suspension on a chevy II. If you want to lower it at will, then consider bags over leafs. Just take some of the spring pack out and replace it with bags. Again, you can go above or behind or in front.
Scotty, First let me say that camaro on the website in your sig is one of the best things I've seen lately! Totally bad ***! As far as the other stuff though, I'm pretty sure I have a decent handle on it. (I may be wrong, as I often am) but I'm pretty sure that fatman uses what appears to be a "half leaf design for the trailing arms so the rear end will still have some give or twist to is latterally. If you set it up as you're suggesting with short tubes fixed at the axle you'd have none of that give or twist which wouldn't allow the body to roll at all, which although I've never tried, would make for a pretty scary ride I imagine. As far as removing some of the spring pack, that's probably not going to work out seeing as the Chevy II's were mono leaf. I could buy some reversed eye de-arched springs, use blocks, and then air over leaf, but then you have a big block on a de-arched spring which does nothing too good for dynamic pinion angle since you've greatly incresed the leverage of the axle moving it away from it's fulcrum on the sping. Lastly the car is going to be used as a slow and low cruiser. 13" wheels, four lug, and a stock L6 engine. None of which is going to put down a ton of stress as far as seam busting torque goes.
Mounting the bag behind the axle should give you better ride quality at the expense of bag travel. The spring should also work pretty much in the stock fashion with the bags behind, as the bag is eesentially replacing the rear half of the spring, as opposed to adding rate to the front half as it would with bags ahead. If the monoleaf was ok on torque before, it should be ok with the bag setup. If you are considering blocks along with the bags, the axle wrap will likely be worse than it would be with a full leaf, as the bag provides no resistance to up travel. Also, if you have to do any welding on the spring for a bag mount, it will have less effect on the spring temper back at the cut end. If you decide to try it, let us know how it works!
if you have a little fabrication skills you can make a 2 link pretty easy. Then you can just purchase a panhard bar and install it yourself. I shy away from 2 links in general, but they have their place for sure.
Certainly didn't mean to jab you. If they are using spring leafs for links, then you are correct, though the effect would be minimal in low power situations. I honestly can't imagine that they would use a flexible link. It introduces an unpredictable element into the suspension geometry. With tubular links, you would definitely want large RUBBER bushings. Note the front end on the Fatman links. I think you could use just about anything in a cruiser and you wouldn't find much to complain about unless you pushed it hard in the corners. Look at this.... (giving away one of my inspirations) http://www.totalcontrolproducts.com/rearcoil.html I thought about one of these on air.
No worries scotty, I didn't take it as much of a jab, I understand that sometimes on here you see people posting up hairball ideas like cutting leaf springs in half and it's wise to get their attention so they don't follow through with a potentially dangerous idea. With that being said, I've been mulling this one over all day at work. Some of the things that I have a hard time getting around are like you said, the pinion angle will be pretty awful for the most part, as the rear end will be pivoting on the front leaf spring mounts. So I figure set the pinion angle at ride height and it will be what it is the rest of the time. I'm thinking that contrary to what Exwestracer said, that even if you run the bags behind the axle I don't see the leaf springs doing any support of the car due to the fact that they rely on being supported at being both ends and deflecting their natural arc. The only variable I see whether mounting the bags in front or in back of the axle it whether or not it supports it against braking forces or accelleration forces? So anyway, that at this point is my main dilema. I think that the "wrap" that half a leaf would still be enough to keep the rear end from rotating too much seeing as I'm running low power, and not a lot of brake/tire. So with that I'm thinking that I might be more inclined to run the bags in front of the axle and the dampers behind the axle, the bags in front giving me better/greater ride height control and the dampers behind the axle so they have better mechanical advantage under braking using their compression force into the ch***is to help keep the axle from wanting to unload under braking. I'm probably way over ****yzing this on.... haha!
Just curious why you think a flexible link wouldn't work? I mean, isn't a leaf spring essentially a flexible link seeing as it's only really "fixed" to the ch***is at the leading end and it's mounted to shackles or sliders in the rear to locate it latterally and still allow it to flex. Also the part about solid links with large rubber bushings? I don't see how that would buy you much as far as allowing body roll, all the forces at that point would be trying to twist the axle housing if the links couldn't twist. I've always heard this philosophy used on I beam front axles as opposed to tube axles when you run split bones or hairpins, because the I beam with twist a bit with nominal loading allowing body roll whilst adding dynamic roll rate to the vehicle similar to how an anti roll bar would as opossed to a tube axle which gives very, very little. Not trying to single you out with another post, my last one was so damn long with my mental babble I didn't feel like editing this into it.
Axle wrap up is the motion you would get, but in a full length semi-elliptical leaf, the other half limits and counters the motion. In the absence of the other half, you could have a wrap-up/rebound thing going on. You can get into the same thing using a quater-elliptical as one link in a 4-link, but the rigid link opposing limits wrap up. I thik if you check with them, it's a plate rather than a just half a spring.
So my question is, why are you modifying the existing suspension ? What does it do wrong, and what effects are you trying to achieve by modification? Are you only interested in looks, or maybe how it rides? Or are you trying to get it to launch harder for drag racing. Or perhaps you don't give a **** how it launches, but you want some real cornering power for road racing. Or do you wish to just spend money on your car so it looks "modified". Many guys are quite happy to just do that, and could not care less how it drives. You say you are looking down the road to modify your car. Yes, but why ??? If you can answer that question, there is no need to ask for advice.
no offense warpspeed, and forgive me if I'm wrong, but this comes off as a little salty? most of what you asked has been answered already, and I'm not asking for how I should build my car, but for a small about of feedback on an idea I'm kicking around about a small part of my car. But,, seeing as I can't sleep and I'm a glutton for punishment, I'll answer your questions I'm modifying the existing suspension primarily for athstetics. It doesn't do anything wong, I'm trying to achieve adjustibility by adding air springs I'm interested in the athstetics, but I don't wan the ride to go completely to hell Seeing as I said it's for "cruising" I'm not to interested in drag racing or cornering (the stock L6 and 155 13" tires would be bad choices for either of those) I don't want to spend much money, I have the fab skills and equip to not pay someone else By down the road I mean in the next few weeks, not years. Why? because I like turning my ideas into my reality Lastly,,,how are you suposed to learn anything if you don't ask for, evaluate, and sometimes take the advice of your peers, who have often times been there, done that, and have valuable insight into what you might be trying to accomplish?
That is an honest answer. I only asked because people's motives for doing car modifications vary so much.
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