Chevelle Triangulated 4 link

[Madspeed]

Question for you number Crunchers and Suspension gurues.

Is the triangulated 4 Link in the Chevelles actually a good system that can be made better by installing tube links with Hime joints?
Oh and making adjustible mounting points to go with it.

Thoughts?

I have a 65 elky to build for somone and I am trying to figure out what I should do with suspension.
Ats Spindles and arms in front But what about rear?

[Gordz32]

the chevelles 4-link is okay and can be improved upon but, it isn't the optimum setup for road race setup. I haven't gotten our car back on the road to test how the art suspension w/tubulars will change the handleing characteristics of the car. But from what I learned at school about suspension design, 3-link and IRS are the way to go for road race performance. It'll depend on what you intend to use the car for. Perhaps be a little more specific about your intentions for the car, and what characteristics of its handling you woul like to improve.

[Mean 69]

Is the customer as stubborn as the builder and won't put a Ford 9" rear in the car!?! If not, well, there's this company in San Diego, you might have heard of them. :naughty:

The problem with any four link setup is mechanical bind in roll, there needs to be something isn the system that will allow the links to lengthen/contract in order for the system to roll, period. This something typically is found in the compliance of the rubber bushings that are used in the factory applications, which frankly, is the best bushing choice for the four link system. Installing poly will tighten things up by reducing the amount of compliance, and therefore introducing mechanical bind sooner. Rod ends or hard bushings like delrin don't offer any compliance. So, how does the thing roll if there is no compliance in the bushings? Simple, something is bending, stretching, compressing. Could be the frame, might be the control arms themselves, could be the actual rear end housing, in practice it's likely to be a bit of all of these. I had a couple early Mustangs that demonstrated very clearly what happens when the system binds up: once the rubber bushings ran out of "squish," and metal to meatl contact occured, the system would bind up immediately, and the booty end of the car would come around in a condition well known as "snap oversteer."

Can they work, well, of course. The Morrison 55 Chevy is a great example. In aggregate, they are pretty simple systems. For road race/pure handling setups though, there are some things that are generally not considered to be overly desireable, in addition to the above. One of these things is the roll center height, it is generally too high, depending upon the orientation of the links (which on the A body cars is not good, quite a bit better on the AME four link due to the lower mounting points of the upper links).

This is the same setup that is used on the late model Mustangs (pre-2005), and there at least three companies that have made a fortune selling systems to replace the rear setup with either a torque arm system, or other variations, it is one of the very first things to be modified for these cars with performance handling as the goal.

Mark

[Madspeed]

Mark FFFS Call me and set me Right
Brother preach the word of suspension Gosple to me PLEASE.

No Ill use a 9" in this car if you have a complete setup for it


My plans for it are to make it stick like GLUE and hook in the 1/4
383 stroker N/A 400 hp,, 4L80 w possible paddle shift
AFX front setup and Z06 brake at all four corners (or the willwoods)

Hit me up fast 818 321 2487 I need to get this job done....

[Skip Fix]

I always thought Heims were based on a spherical bushing and could rotate as not to bind. Global shows there spherical leaf spring bushing doing that.

[Madspeed]

Heh I would have said the same thing But I know Mark isnt retarted.
his post was just an oversight.

=)

[Gordz32]

Sounds Like you need a Lateral dynamics 3 Link Brotha!:firefire:

[Mean 69]

I always thought Heims were based on a spherical bushing and could rotate as not to bind.

Yes, they are based on a sperical joint, and they don't allow bind in rotation (unless the loads are so high that friction takes over and the ball can't rotate, which is basically never going to happen unless really bad poop has hit the fan, i.e. big crash). The issue isn't with the joints, it's with the beam aspect of the arms them sleves. In short, when you roll the system, at least one of them needs to either get longer, or get shorter, or the system won't roll. If everything were perfectly rigid and nothing was allowed to flex in a four link with rigid joints (i.e. rod ends), the system would NOT roll, period. The reason that they do roll is that something IS flexing. This is very most likely the reason that rod ends get such a bad reputation from folks, most of them are put onto drag race type setups, and when driven on the street, the overall setup is really harsh in normal driving, mostly due to bind. I run all sphericals on my own car, and I can tell you it's not harsh at all. But, my setup doesn't bind, by design.

Mark

[Madspeed]

Yes, they are based on a sperical joint, and they don't allow bind in rotation (unless the loads are so high that friction takes over and the ball can't rotate, which is basically never going to happen unless really bad poop has hit the fan, i.e. big crash). The issue isn't with the joints, it's with the beam aspect of the arms them sleves. In short, when you roll the system, at least one of them needs to either get longer, or get shorter, or the system won't roll. If everything were perfectly rigid and nothing was allowed to flex in a four link with rigid joints (i.e. rod ends), the system would NOT roll, period. The reason that they do roll is that something IS flexing. This is very most likely the reason that rod ends get such a bad reputation from folks, most of them are put onto drag race type setups, and when driven on the street, the overall setup is really harsh in normal driving, mostly due to bind. I run all sphericals on my own car, and I can tell you it's not harsh at all. But, my setup doesn't bind, by design.

Mark

Hey You Freak Sandwich!!!!
Will you call me allready so we can discuss this LD setup for this elky?


=))))))))

[Madspeed]

Sounds Like you need a Lateral dynamics 3 Link Brotha!:firefire:
At the time of o/g post i was unaware that mark had somthing for an Elky

:headbang:

[Gordz32]

I'm not sure that he does have a setup for an elky, but its nothing a little fabrication won't fix. you might have to cut the bed, not sure. Talk to the man:smoke:

[TUBED]

Madspeed,
Check with Wolfe Race Craft or www.wolferacecraft.com, they have single and double adjustable upper and lower rear 4130 moly arms with spherical rod ends. They are on sale through December at 20% OFF.
These are nice quality parts that I've purchased for my ride.
Gerald

[Marcus SC&C]

As usual Mark`s right on target here. The arms need to be free in torsion and especially the uppers do need to change (very very slightly) in length to eliminate binding. Heims (spherical rod ends) are not the answer here. While they`re free in torsion they`re absolutely rigid axially. We`ve had excellent luck with Currie Currectrac arms http://www.scandc.com/currectrac.htm The Johnny joint allows up to 30* of flex and the urethane races and the bushings on the axle side allow just enough length change to reduce the binding to an acceptable level. Remember on a well set up car we`re only dealing with maybe 2*-3* of roll and 3" or 4" of vertical travel on the road/track. If the suspension binds just a little when the car is up on the lift who cares? It`s still an imperfect solution but they make a suprising difference and allow about 10* (about 3X what you need) of roll with no noticable resistance. The roll center remains an issue for several reasons but we have customers running them with good real world results in auto X,on the Autobahn and open course road race cars. For a hardcore car that sees a lot of track use a torque arm or 3 link (my choice) set up would still be a better option though. Mark SC&C

[MonzaRacer]

I actually had a fella fix up a set of Southside Machine Bars for me with spereical aircraft bearings in front for me to install on friends drag car and the uppers we build adjustables(to set pinion angle) with them on both ends. we could actually roll car over to jam tires firmly(ever try to pry new wheels and tires out of wheelwells not easy) and never bound the suspension,,, just the darn tires! haha.
I would never have bekieved it would do what it did, he now also has cool ride on his car and cant believe how good it sticks (better now that he dumped his junk A$$ goodyear F1's for some Bridgestone SO3's , kind of waitning to see what comes out now after SO3's have been dicontinued. But for me I actually wish BSFS had a good low pro in my size for my truck in the Turanza lines.
Just remember that while a abody 4 link might bind some after you set the spring shock swaybar package up your not going to get as much body roll and even less bind,
A complete redesign isnt required unless your going to beat on it on a road course in a series in my opinion.
Good luck
Lee

[Norm Peterson]

. . . If everything were perfectly rigid and nothing was allowed to flex in a four link with rigid joints (i.e. rod ends), the system would NOT roll, period. Actually, it will. But not about the static roll center or axle's static roll axis. And it may involve some, ummm, unusual motions.

Here's how.

A stick axle has six degrees of freedom, and requires that four of them be controlled. Two wheel bump and roll are the only ones intended to be left free. A link that's spherically pivoted at both ends can only resist one DOF, meaning that precisely four links will provide the required amount of axle control.

The lower arms control fore/aft movement of the axle ends. This controls both bulk fore/aft axle motion and axle steer.

Since it only requires one upper link to then control pinion angle, that becomes the job of just one of the uppers.

But that still doesn't nail lateral location down. That requires a fourth link, not parallel to any of the others. The fly in the ointment with the converging/triangulated uppers is that the axle may have to move laterally a bit in order for this 4th link's axle pivot to find a position that's agreeable to the other three (think 3-D spherical arcs with both the chassis pivot points and the axle pivot points remaining in their respective planes). There will be slight pinion angle and axle steer consequences. The point about which the rear of the sprung mass is seen to roll will almost certainly NOT be about the static position of the conventionally defined roll center.

Apparently, all-rod-ended converging 4-links are used in a few circle track classes, so it actually will work (somewhere I have a mathematical derivation that was sent to me but which I haven't yet managed to struggle completely through).

Anyway, all rod ends is not really a streetable arrangement, and as soon as you introduce compliance, suspension accuracy starts to go away (though the requirement for lateral axle motion should decrease). The OE's simplified construction that uses cylindrical bushings starts to add resistance in more than just the four degrees of freedom that you want controlled (less control, more "bind").


Norm

[sinned]

Apparently, all-rod-ended converging 4-links are used in a few circle track classes, so it actually will work (somewhere I have a mathematical derivation that was sent to me but which I haven't yet managed to struggle completely through). I can back that up with real world experience.


Anyway, all rod ends is not really a streetable arrangement, and as soon as you introduce compliance, suspension accuracy starts to go away (though the requirement for lateral axle motion should decrease).
NormI guess "streetable" is open to interpretation. I ran mine that way for over a year and never had a problem, in fact I think NVH was less of issue after replacing the 35 year old rubber peices and stamped links.

[Skip Fix]

There is a circle track company that sells press in bushings with sphericals for A and G body control arms