3 Link, Stop me before it's too late...

[ITLBTU]

As my '69 Camaro project is getting deeper every day, I keep pondering the 3-link suspesion on the rear. Would it be a good idea to weld 2 pivot mounts on the top of the axel tube and connect it to a wish-bone shape uca with a single point to mount it on top in front. I'm planning on using heims on both ends. My idea is to do minimal cutting and hopeully make this almost completely bolt in while being able to get the geometry correct... Go ahead and school me...

[Damn True]

If you are considering a 3-link I would look to Lateral-Dynamics. The engineering is done and the results are solid. Yes the initial investment would be higher, but if you factor in your time required to go through the trial and error of developing your own system, IMO you'll be money and time ahead by going with the L-D version.

[ITLBTU]

If you are considering a 3-link I would look to Lateral-Dynamics. The engineering is done and the results are solid. Yes the initial investment would be higher, but if you factor in your time required to go through the trial and error of developing your own system, IMO you'll be money and time ahead by going with the L-D version.

That isn't an option for me. I'm quite sure that I can build my own for maybe a few hundred dollars, as apposed to over $6k. I also want it to be less intrusive as their's.

[baz67]

I am not exactly sure how you plan on doing this???? Where do you plan on putting the upper link? They way you are explaining the lower links it sounds like they will be above the axle and attaching to the body at a single point. If so, how do you plan on working around the driveshaft? What about lateral restraint?

[TLWiltman]

The trouble with not intruding into the passenger compartment on these cars is that you end up with a very short upper link (excessive pinion angle and anti-lift/anti-squat changes in suspension travel). What you're talking about is probably gonna result in some serious geometric compromises. Do you have any suspension design software (WinGeo, Suspension Analyser)? If not, you may want to start there. It's money well spent.

As far as a "wishbone" upper link. I don't really see the point. Three links work just fine with a single attachment point at both the rearend housing, and the chassis. So, I'm just not sure what you're trying to achieve. Maybe a bit more explanation on that might help.

I guess what I'm trying to say is. I admire the guts it takes to go your own way. But, at the same time, I'm concerned that there are many more wrong ways to build a 3-link than there are correct ways to do it. Just want to make sure you're being careful about this.

[Camaro Zach]

As far as a "wishbone" upper link. I don't really see the point. Three links work just fine with a single attachment point at both the rearend housing, and the chassis. So, I'm just not sure what you're trying to achieve. Maybe a bit more explanation on that might help.

wishbone style upper link will eleminate the need for an added lateral locating device (panhard bar, watts link, ect.)

[Beige]

I am not exactly sure how you plan on doing this???? Where do you plan on putting the upper link? They way you are explaining the lower links it sounds like they will be above the axle and attaching to the body at a single point. If so, how do you plan on working around the driveshaft? What about lateral restraint?

I think he was only describing the upper link.

As far as a "wishbone" upper link. I don't really see the point. Three links work just fine with a single attachment point at both the rearend housing, and the chassis. So, I'm just not sure what you're trying to achieve. Maybe a bit more explanation on that might help.

He's using the wishbone to locate the rear laterally.

I don't think it will be as simple as you think, ITLBTU. But by all means, keep working at it. Just get some verification before sticking it in your car.

[1971novaSS]

Hey buddy, Looks like you and me are going the same direction.

I am installing a 3-link into my 71 nova. I have 32 inch lower links and will have hopefully a 16-18 inch upper link. I have fabbed up the bracket to attach to the rear end pumpkin that will optimize the amount of "room" or space that you have to work with. My car will be very low so the other end of the link will be right behind the seat, literally RIGHT BEHIND IT!

I would try and persway you not to use the wishbone setup, im not sure you or I have the space. I am going to run a panhard bar for to locate the rear-end.

As far as a "wishbone" upper link. I don't really see the point. Three links work just fine with a single attachment point at both the rearend housing, and the chassis. So, I'm just not sure what you're trying to achieve. Maybe a bit more explanation on that might help.

EXACTLY, No point for wishbone! Use panhard.

I have the lower links finished and i am almost finished with the upper link. This will work with the STOCK rear seat in! I ALSO have a mini-tub as well.

And my rear-end geometry will be just fine. If you need any help or advice PM me and i can send some pics your way later on tonight.

And the 3-link is definently the way to go for handleing and rear end articulation ability. Oh and i will be using Hiems for now, But if you have the money use the Johny Joints. Johny joints have a 33 degree flex while hiems only have 22 degree.

[David Pozzi]

wishbone style upper link will eleminate the need for an added lateral locating device (panhard bar, watts link, ect.)

Look at a 1959 Alfa Romeo Gullia Spyder rear axle, they use such a device. I believe it is a stamped A arm that pivots off the unibody just ahead of the axle and above the axle tube. It attaches to a bracket on the left hand tube with a good sized rubber bushing.

The Factory Five Kit Cobra uses a rearward offset housing bracket for the top link. It reduces the intrusion of the bracket into the cockpit.

[1971novaSS]

Dave, Im not sure i am understanding the information on the wishbone.

Either way you go, your over-all lenght will be the same. Just with three connecting points rather then two.

Wouldn't it deem more time consuming and complicated to fabricate two mounting brackets for the rear-end housing then it would if you just slapped a panhard on?

Or are you saying that you still will only have one connecting point to the top of the housing, and two connecting points to the front crossmember.

I just think the fabrication needed for the wishbone style either way would seem to be more complicated then just using a regular top link with a panhard rod setup.

And wouldn't the wishbone setup subtract the available rear-end articulation? Isn't that the purpose of the 3 link, to increase the movement of the rear-end, and ultimatley enhancing the handling of the vehicle? Once you add that extra link to locate the rear-end you just took away a good amount of available movement.

Maybe im going nuts? Definently possible. haha

[baz67]

Alright I see the UCA now. I guess I missed it when I was trying to visualize what he wanted to do. However, that still does not explain how that setup is out of the way of the driveshaft. Also, with the UCA so low what about the SVSA length.

Unless I am totally missing what he wants to do how would the forward mount of the wishbone UCA be mounted without major work. Furthermore, if the wishbone UCA has double duty as the lateral restraint, how does that work? He states that he is using heims on both ends. I cannot visualize anything preventing the axle to move laterally.

[ITLBTU]

Actually, I was planning on attaching the 2 sided part of the wishbone uca to the axel tubes on either side of the cast housing. That way I can place the pivot point lower on the rear end, and the forward mount on the chassis. I'll attach a pdf of what I have so far. Ignor the short uca that is drawn. I need to verify the upper attach point on my Camaro yet. I plan on making bolt on brackets for the lca on the axel, and using the spring mount on the front. I do plan on using as long of a panhard bar to locate the rear. That would be adj for tuning. Both vet. and length for horiz. location.

[Derek69SS]

A wishbone will laterally locate the axle, so a panhard bar would not be necessary, and using one will create conflicting roll-centers.

[jerome]

here is a picture for those not understanding what he means:

this method does provide lateral restraint, but in my opinion, not as good as the method below.


here is a better way to do it: connect the two points to a crossmeber, connect the point shown at the top of the below picture to the rearend.
the two points connected to the crossmember can be an axial bushing, but the single point at the top of the pic MUST be a spherical joint


this does not reduce articulation in any way. the only way it would do that would be if the joint at the top of the rearend was a non-sperical joint.

here is something to ponder about: disregarding packaging restrictions, is a watts link any better of a lateral location device than a wishbone top link?

Jerome

[baz67]

Ok, that is what I thought. I would not put much faith in it doing a good job with lateral location. It seems there would be a lot of bending force that the single pickup needs to keep in check. But that is just me.

Yes, I feel a watts would be better because you can change RCH without having to worry about swing arm geometry.

[Steve1968LS2]

That isn't an option for me. I'm quite sure that I can build my own for maybe a few hundred dollars, as apposed to over $6k. I also want it to be less intrusive as their's.

$6k???

uh, thier kit is $3500 or so. Even if you build your own you will still need a differential

Anyways, good luck with the project.. I'm sure it will be a learning experience. Keep us updated!

[David Pozzi]

A wishbone will laterally locate the axle, so a panhard bar would not be necessary, and using one will create conflicting roll-centers.

I don't think there would be a conflict of roll centers because without a panhard bar there is no other "natural" roll center to conflict with like there would be with a leaf suspension. But the RCH would be several inches higher than a leaf or normal panhard/watts link rear.
David

[Ripper]

wishbone style upper link will eleminate the need for an added lateral locating device (panhard bar, watts link, ect.)

But it will also give you a very high roll center which affects handling. I would say a panhard bar or a watts link (with the spindle attached to the body, not the rear end) would be a better idea.


I was going to build my own 3-link but ended up buing an IRS instead. However, a three link is a very good solution. Try to attach the upper link in the center of the rear end. On top of the housing would be a good idea. Go for the same length as the lower arms and cut up the drive shaft tunnel. If you don't like the solution, hide it with a center console for the rear seat! ;)



Is the upper link what I think it is? Some kind of delrinbased rod end? Where can I get those?

[Norm Peterson]

I don't think there would be a conflict of roll centers because without a panhard bar there is no other "natural" roll center to conflict with like there would be with a leaf suspension. But the RCH would be several inches higher than a leaf or normal panhard/watts link rear.
David

With a wishbone and the two other links you have two points of lateral constraint defined. One is the wishbone's single pivot, and the other is the virtual intersection of the other two links (which may be "at infinity"). That gives you the suspension's roll axis, and, at the intersection of this axis with the YZ plane containing the axle, the overall roll center. Adding a PHB or any other constraint will "overconstrain" such a system, which will then only work by virtue of compliances and geometric coincidence.

Mathematically, the three elements in a wishbone arrangement fully constrain the necessary four degrees of freedom. In this case, the wishbone is responsible for two of the four constraints instead of just the one constraint provided by a single upper link. Y-axis axle rotation (aka pinion angle) and lateral translation.

I agree that the combination of desired axle roll steer and driveshaft location will likely conspire to drive the roll center up to or above the top of the pumpkin.


Norm

[David Pozzi]

With a wishbone and the two other links you have two points of lateral constraint defined. One is the wishbone's single pivot, and the other is the virtual intersection of the other two links (which may be "at infinity"). That gives you the suspension's roll axis, and, at the intersection of this axis with the YZ plane containing the axle, the overall roll center. Adding a PHB or any other constraint will "overconstrain" such a system, which will then only work by virtue of compliances and geometric coincidence.

Mathematically, the three elements in a wishbone arrangement fully constrain the necessary four degrees of freedom. In this case, the wishbone is responsible for two of the four constraints instead of just the one constraint provided by a single upper link. Y-axis axle rotation (aka pinion angle) and lateral translation.

I agree that the combination of desired axle roll steer and driveshaft location will likely conspire to drive the roll center up to or above the top of the pumpkin.


Norm

Norm,
I was saying that there should be no conflict of roll centers with a wishbone upper link, and NO panhard bar or other lateral locator.
David