I have an idea to reduce or eliminate the roll bind in the rear suspension... Tell me if you think it will work.
It seems to me that much, if not all of the bind comes from the links themselves. Since they cannot twist, the bushings have to compress when the body rolls. If there were a modification to the links themselves to allow one end to rotate relative to the other, do you think it would solve the problem?
Unlike the 3-link set-up, this would not induce roll-steer. I also wonder is this same mod would allow the Watts linkage to operate more freely. If the Watts binds because the axle rotates as it move up and down, then it would stand to reason this technique would work just as well.
I'm not sure I can describe the picture in my head, but I'll give it a try. Remove ~ 6" from one end of the link. Either make a new bushing ring or cut the old one off of the removed end. Weld to that ring a squarish bracket (which would make it resemble a D-handle on a shovel). In the center of the "D", weld a piece of thick round tubing about 2" long, which will be the "female". Make a shaft which can be attached into the other end of the cut off link. Fashion this shaft so it rotates freely in the female bushing, is threaded on the end, and is retained by a nut (which ends up being inside the "D"). Lock the nut with a roll pin, cotter pin, Loctite, or maybe just a jam nut. It would take careful workmanship to eliminate any slop, possibly a belleville washer to help absorb any end play. Since the original bushings remain on each end of it, it should be isolated from any hammering.

Well, what do you think? If you blow holes in the idea, you'll save me a whole bunch of work.

Kerry

 

Sounds reasonable to me, but I dont understand your concept, I cant seem to visualize it.

Why not use rod end bearings? they allow for mis alignment...that's one of my ideas.

 

Rod ends are not so good for a daily driver. They transmit a lot of noise, and require frequent lubrication because they have no boot to keep water and dirt out. They would work quite well other than that.

Kerry

 

well i have no idea if that would work, but i would suggest posting a link to it in the suspension/wheels tires or maybe even racecare tech
you might get some more responses that way.

gamble

 

True, but they have teflon coated ones that are much quieter, and dont require lubrication.

 

It sounds like an interesting idea, which may correct some of the challenges.

Yet, as I understand the problem with the rear links are that the upper and lower links move in different arches and on different axis. There differing arches are due to there different lengths, and since the uppers are mounted at an angle they move in a different axis as well. So, the binding is caused by a rotational problem, as well as an alignment axis problem. I think that your solution would help with axis rotation, but not the differing arches of rotation. (Does that make sense?)

The same is actually true of the watts links as well. Since the upper and lower links are different lengths they have different arches of movement.

 

That makes sense, Cone. I hadn't thought of that. Oh well. I might give it a try on a 3 link setup.

Kerry

 

Wait a minute... The upper links are at angles, but aren't the pivot points all parallel? (the links have a kink in them?) If this is the case, then any twisting motion on the upper links would be exaggerated because of the kink.

Kerry

 

Kill no cone your right about different axis of rotation. Thats why I wanna use rod end bearings. They will allow the links to twist and hopefully not bind.

 

Kerry, get the torch and the odds-n-ends bucket out and fab some up. From your description I saw clearly what you were getting at and I think it'll work to eliminate quite a bit of binding.

My suggestion would be doing the Watt's first, as it binds so easily.

Now what you need is some sort of test to measure the amount of binding before and after the operation...

 

Yes, Kerry, that is the key to the binding of the rear end. The bind caused by the twist is the biggest issue. Not only are they 1. not parallel, 2. at different angles, but, 3. the control arms are different lengths. You cannot make a rear end move straight up and down if the control arms are differing lengths. Each length has its own arch. Once you have all of that straightened out, you have to look at the bind in the watts link.

Carl, I think the rod ends would relive some of the bind caused by the twist. But, I think we are still left with the differing rotation arches caused by the different length control arms.