Was wondering if this was typical or if I have done something wrong. I have coil conversion on my toyota (dana 44 front end) and when I steer it hard to the right, the tire hits the lower link bar but when I steer it hard left, the other tire doesn't hit the link bar. When I steer it hard right and watch the front axle I can see it shift to the right an inch or two. I am running bushings at the frame and heim joints at the axle is it just the small amount of bushing compression that is allowing it to shift a bit, or have I not triangulated the v links enough? My front v links are about 41 inches long and 28 inches apart at the frame and about 2 inches apart at the axle. Any remedy to fix this? Would running heim joints at both end help or jonny joints? Or are the links too long and just not spread apart enough? :confused:

hard to say with out seeing it but my guess is bushing deflection.

This is not typical. It does sound like a bushing deflection problem. Are you using rubber or poly U.

I'm using poly bushings as I thought they would have less deflection. when I stuffed them into the tube it seemed like a tight fit so there shouldn't be slop between the tube and bushing either. I'll try to get some pics of the front end flexed and at rest so you can see what I mean.

That is not surprising with that link geometry, If the movement doesn't bother you then leave it. If you end up reworking it you might consider a 3 link with a panhard bar in the front. That way you can design the panhard bar to be the same length and angle as the drag link and you will have less bump steer. This will also allow you to get full steering when completely articulated, since it sounds like right now your steering is limited by the steering box. I am assuming you have crossover steering, maybe I should wait for the pics.

Yea, I missed that part about it being in the front end. You should defiantly be running a panhard.

How can a panhard bar work with a triangulated 3 link? It seems like it would bind when the axle moves up and down. :confused:

yep you don't want to run a panhard with a triangulated 4 link. With a 3 link and coils you need it. there is no way to make a triangulated 3 link that would control the side to side movement of the axle.

Basically 3d space is a 6 degree of freedom system with motion in x, y and z directions and rotation about x, y and z axis. you want to eliminate 4 degrees of freedom on a solid axle and allow rotation on one axis(articulation) and translation on one axis (compression/ droop) It takes 4 links to do this. If you use more than 4 it will bind (unless there are redundant links that travel the exact same arc) you can use a 3 link with a panhard or a triangulated 4 link or you can use a wishbone and two links, where the wishbone essentially counts as two links. Also a radius arm counts as 2 links since it is essentially rigidly mounted to the axle. There are other options but those are the comonly used ones.

Shit-can the bushings and it's fixed

Never use bushings on the front triangulated links, espeacially with a cross-over steering system
ericfilar@fatcity

pannard bars:rolleyes:

Ok, so in a three link, you've got 2 points at the axle that converge to one point at the between frame mount. This allows the axle to move in all but one plane(front to back), then the pannard bar controls side to side. Does this eliminate the 4 degrees of freedom correctly? Thanks
ROb

Broncobob, See previous post.

Originally posted by broncorob
Ok, so in a three link, you've got 2 points at the axle that converge to one point at the between frame mount. This allows the axle to move in all but one plane(front to back), then the pannard bar controls side to side. Does this eliminate the 4 degrees of freedom correctly? Thanks
ROb

Yep that is the kinematic equivelent to a torsion tube like some older chevy's and unimogs used. It works good. Some road race guys use the exact setup you describe because it is easy to move the instant center the roll center height and the roll axis with just a couple adjustment points.

Thanks for the reply guys. I'll get some pics up so you can better see what I am talking about and have a better idea on how I have FUBAR'ed my linkage. I can adjust the steering and live with the movement, but I would of course prefer that the movement not be there. And yes I am running cross over steering. I didn't put in a panhard because I have no solid place with which to weld the axle mount with the setup that I am running so I choose 4 link instead. I'll try to get some pics up soon.

Originally posted by Gordon


Yep that is the kinematic equivelent to a torsion tube like some older chevy's and unimogs used. It works good. Some road race guys use the exact setup you describe because it is easy to move the instant center the roll center height and the roll axis with just a couple adjustment points.

Thanks Gordon:beer:

Originally posted by FatCity
Shit-can the bushings and it's fixed

pannard bars:rolleyes:

So you have setup vehicles with a triangulated four link front and crossover steering and they get full steering at full articulation, both ways and full droop? That is pretty impressive you must use a long pitman arm and short steering arms. Your stuff is top notch so I believe you if you say you can make it work, but I would like to see it.

No!!

You can't get full steer out of a cross-over/conventional triangulated 4-link,

but you can come close enough, you'd never be able to tell the difference.

However thats not what I was typeing about.

You're main problem is the lateral movement... shit can the poly...

We'll talk about cross-over/steering options when you're done.
eric filar@fatcity

Originally posted by FatCity
Shit-can the bushings and it's fixed



pannard bars:rolleyes:

? so what if I can the poly bushings and replace with heim joints and it still gets some movement? Then can I conclude that I have not triangulated it enough? I could just adjust the linkage at the pitman arm and the tire wouldn't rub and it would still turn better than most vehicles as I am running full width so I'll try this tomarrow before I go cutting the bushings off and replacing them with heim joints. only the inner side lugs rub on the link so it can't be all that much. How much lateral movement is acceptable? I guess whatever I can live with right? Thanks for the replies.

Originally posted by coiled
? . How much lateral movement is acceptable? .

1/4" is pushin it

Originally posted by coiled
? Then can I conclude that I have not triangulated it enough?

It seems O-K

OK so in my stupidity I forgot to set the drag link when I did the coil conversion so I went out and set it so that it turns equally left to right and wonder of wonders I have no rubbage whatsoever. Yeehaaw! Still when I crank it hard right, Like the last 1/2-1/4 turn I can see the body shifting over a bit but when I turn it just normal it doesn't move that I can see. So what do you think? Seems to me that if it were triangulated enough it shouldn't have any lateral movement using either bushing, heim, or johnny joints yes? It is a trail only machine so it doesn't matter to me if the front end does what it does as I don't drive it over 20 mph. In the future is there some sort of figure that tells me how much triangulation I need with the length of links used?

Originally posted by coiled
OK Still when I crank it hard right, Like the last 1/2-1/4 turn I can see the body shifting over a bit but when I turn it just normal it doesn't move that I can see.

In the future is there some sort of figure that tells me how much triangulation I need with the length of links used?

It sounds like your turn stop is hitting before your steering box. As you turn the wheel, the box is pushing against the whole axle.

Id be interested in info about the angles too...

Hey that's an intersting concept. I'll have to check that out, kind of hard for me to tell by myself because I can't get the steering wheel to lock up at the far right or left, ends up locking before then but I'll check that out with someone turning the wheel. Would seem to make sence because the axle isn't really being pushed while I turn until that last little 1/4 turn or so. Thanks.

coiled,
i just now seen your thread. don't know if this will help but here is a write up on my front 4 link.
http://w3.one.net/~marc/broncohio/tech/fourlink.html

steelman