Triangulated 4 Link Qs

[OustedFairlady]

I'm working on something of a project, specifically, back halving and installing a cut down 31-spline Ford 9" axle.

 

I know there will be people disagreeing with me, but this is the route I've decided to take with my Z. I'm installing a Toyota 7MGTE, and in the interest of traction, I've decided to install an entire new rear suspension setup. I know the factory stuff is perfectly capable, but again, this is the route I've decided to take.

 

Back to topic:

I realize there are a lot of measurements and a lot of information one needs before undertaking this sort of project, but one must start somewhere. Just to serve as a reminder, as much to self as would-be advisors, I am NOT a professional fabricator, although that is a field I am intensely interested in. My mechanical aptitude is fairly high, as I'm an ASE certified mechanic with some experience in the field. However, I am by no means a genius, nor do I claim to be. I'm here for answers, not to push my idea of the truth on everyone. If I'm wrong, please present evidence to that fact, as I am interested in learning, not arguing, and evidence is the ultimate impartial judge.

 

Now...I'm familiar with the concept of a triangulated four link suspension, and to clarify my plans, here they are:

 

I'd like to reinforce the chassis by, for all intents and purposes, adding a ladder bar frame to the car's existing unibody construction. I.e., I'd like to use metal stock to tie the front and rear of the car together. I was informed that the S30 chassis isn't the strongest thing in the world and could do with reinforcement before applying any sort of horsepower. It was suggested to me by another member that has undertaken the 7M swap, and in the interest of A) safety and B: reliability, I'm going to do this.

 

I have a cut 9inch housing and axles with differential (posi, of course).

 

 

This illustration depicts fairly accurately what I'd like to do, albeit on a different chassis.

 

In any case, my questions:

 

1) Does anyone on here have experience with triangulated four links?

 

2) Does anyone on here have experience with heim joints? To elaborate:

 

I'm considering the use of heim joints instead of poly bushings. However, as I understand it, heim joints have a certain range of misalignment, as it's referred to, which, in most cases I've found ranges between 11 and 17 degrees of deflection. Will a triangulated four-link setup be able to move enough to exceed this 11-17 degree maximum? There are high-misalignment heim joints available (for a fairly substantial price) whose angle maximums fall between 18 and 22 degrees of misalignment. Would the normal heim joint be suitable for a this setup, and would it likely experience higher alignment angles than it is capable of withstanding?

 

3) I'm considering using T303 stainless steel bar stock to build the links, rather than tube. This would allow me to simply mill down the ends and thread them for the heim joints. Is this ill-advised? I understand weight may become an issue, although I didn't see how four stainless steel bars would create that large of an issue in a gutted '71 Z. However, again, I bow to the wisdom of those with more experience, and would happily admit my error if it is. I have access to a lathe and all equipment needed for welding or fabrication.

 

Here is a link to where I intended to purchase my heim joints, if I decided to go that route: Poly Performance

Edited February 12, 2011 by OustedFairlady

[Snailed]

My $.02 I deal with 4 links at work frequently.

 

Heim joints are the way to go for a setup that doesn't bind. A triangulated four link slightly twists all the end links when one wheel travels a diferent ammount than the other. You won't even be close to the maximum range with regular heims on a car. Those smaller poly bushing ends will bind a bit, but they do make for a little quieter ride.

 

I wouldn't use stainless bar stock for the links. The easiest and least expensive way is to buy swedged tubes of the right length. They are amazingly inexpensive and would save you pounds of unsprung weight. Sometimes we fabricate cromoly arms using premade tube ends but that's overkill for the most part. Another option is using DOM tube that can simply be tapped for the heims. Easy to make and still not as heavy or expensive.

[OustedFairlady]

My $.02 I deal with 4 links at work frequently.

 

Heim joints are the way to go for a setup that doesn't bind. A triangulated four link slightly twists all the end links when one wheel travels a diferent ammount than the other. You won't even be close to the maximum range with regular heims on a car. Those smaller poly bushing ends will bind a bit, but they do make for a little quieter ride.

 

I wouldn't use stainless bar stock for the links. The easiest and least expensive way is to buy swedged tubes of the right length. They are amazingly inexpensive and would save you pounds of unsprung weight. Sometimes we fabricate cromoly arms using premade tube ends but that's overkill for the most part. Another option is using DOM tube that can simply be tapped for the heims. Easy to make and still not as heavy or expensive.

 

In other words, 11-17 degrees of travel is adequate for a four link, and the high-misalignment type joints aren't required?

 

As for the tubes, where might I find such a thing? I'm not going to rally the car, although drag launches with two step would be likely on occasion. I should be making four hundred or so, but I'd like to build the suspension to hold a good bit more if possible.

[OustedFairlady]

No input? Anyone?

[Snailed]

In other words, 11-17 degrees of travel is adequate for a four link, and the high-misalignment type joints aren't required?

 

As for the tubes, where might I find such a thing? I'm not going to rally the car, although drag launches with two step would be likely on occasion. I should be making four hundred or so, but I'd like to build the suspension to hold a good bit more if possible.

 

yeah, all heims have 360* travel in the main direction you are using them. Think about how much side to side travel poly bushings have...

.

Sorry I mispelled swaged tubes. Google it. You probably want 1" ones which will fit 3/4" heims. I think 12" x 1" DOM tubes are about $11 each. Also lots of people use pre tapped, aluminum hex tubing, also cheap. If you are going for big power later, think about some larger diameter DOM tubing with weld in ends. Still cheaper and lighter than stainless bar.

 

If you figure out what lengths you need (hole to hole) we stock all this stuff and I can TIG weld them up for you and ship four tubes with eight 3/4" rod ends & jamb nuts included.