Do I have a bad anti-wrap bar design, with pics?

[mrk5]

Kert,

I understand conceptually what you're getting at, but there are a couple of things to consider....

1. The springs in your drawing would be a lot thicker and more substantial than what you've shown.....ie. stiffer. And the forces aren't pushing the spring UP...they are moving laterally, trying to compress the distance between the spring eye and the springpad.

I partially disagree. I believe there is going to be some upwards force on the springs because the axle is rotating, not trying to slide laterally.

I think the springs can still warp because of the rear shackle allowing the sping to move, as Kert shows in his drawing.

I think that ntsqd's design would greatly decrease axle wrap, but not eliminate it to the extent the standard design does. Given enough torque, wrap will still occur. I think that is why miniwally pointed out the most successful single link designs he's seen have the link coming off the bottom of the axle. That would help inhibit the actual axle rotation.

I'm not an expert, but I am a thinking man...

 

[miniwally]

Those that have the TTC video of Wally in the drag race in 2001 watch it. Post up what you see as Stephen loads the drivetrain to prevent shocking it.

That is what happens with a single link on the bottom. The other hand is that I watched a rig with those same traction bars shown above on Wally take out a rear axle yoke with the vehicle in reverse because the springs can't take the compression forces.

A single mounting point below the axle works but raises the body on acceleration, and still will have some bad axle wrap in reverse.

A single link mounted above the axle will have some wrap forward but will suck the body down in reverse.

Been there seen it done it.

 

[slyguy_22]

i was looking into a similar setup, but i think i might stay away from that idea now. What about a basic latter bar setup? Wouldnt that work fine? that would be out on the axle tubes and wouldnt put stress on the center but even it out on each side and still allow for flex? Im not sayin it would work im asking what you'll think? im my mind it seems like it would work

 

[mrk5]

Those that have the TTC video of Wally in the drag race in 2001 watch it. Post up what you see as Stephen loads the drivetrain to prevent shocking it.

That is what happens with a single link on the bottom. The other hand is that I watched a rig with those same traction bars shown above on Wally take out a rear axle yoke with the vehicle in reverse because the springs can't take the compression forces.

A single mounting point below the axle works but raises the body on acceleration, and still will have some bad axle wrap in reverse.

A single link mounted above the axle will have some wrap forward but will suck the body down in reverse.

Been there seen it done it.

No one will believe a mall crawler like you!

 

[ntsqd]

I partially disagree. I believe there is going to be some upwards force on the springs because the axle is rotating, not trying to slide laterally.

I think the springs can still warp because of the rear shackle allowing the sping to move, as Kert shows in his drawing.

I think that ntsqd's design would greatly decrease axle wrap, but not eliminate it to the extent the standard design does. Given enough torque, wrap will still occur. I think that is why miniwally pointed out the most successful single link designs he's seen have the link coming off the bottom of the axle. That would help inhibit the actual axle rotation.

I'm not an expert, but I am a thinking man...

Those with the low link(s) are most successful because the arrangement puts the springs in tension rather than compression. That is without question the most desirable arrangement. It also has ground clearance - break-over angle issues which make it a non-starter for a lot of people.

This is the basic short-coming of an A-bar design:

Let's say that you have a 14bff and you bolt a 3 foot long tube to the axle hsg using the pinion carrier bolts. Ignore for the moment what that does to the driveshaft.
Now visualize the suspension moving. Ignore articulation for the moment. Picture driving across some railraod tracks somewhere. The suspension compresses and then extends, but because the spring perch part of the springs don't change their angle relative to the ground by very much neither does the pinion angle change very much.
Now back to the 3' tube we bolted on to the axle. Since the pinion angle didn't change much neither did the tube's angle.

EDIT: So the front end of the tube moved the same distance that the hsg did - or very close to it. This means that the front end of that tube is still nowhere near the point in space that is the center of the travel arc.

Since the purpose of that tube is a traction device you put an SRE or a JJ or whatever at the front end of it and attach that to the frame.
Wait, the pinion angle didn't change. So the tube angle didn't change. Only now the front end of the tube is fixed relative to the frame, so now the tube angle (relative to the ground) HAS to change when the suspension as a whole either extends or compresses, and if it is changing then so is the pinion angle.

BUT the only way that the pinion angle can change is if the angle of the spring perch part of the springs changes. With the front end of the tube fixed to the frame it then has to force the spring perch part of the springs to change their angle. So not only is the part that was added to the truck to stop spring wind-up now actually causing spring wind-up it is also putting huge loads on all of it's mounting points.
Those huge loads are what is tearing up things.

 

[79k20350]

Would running a link on the top one side and on the bottom on the other sovle the issues at hand? That rather then running 2 on the top or bottom.

 

[ntsqd]

I've not forgotten this. Nor have I had time to work out the math stuff. As to someone already running such a design, there at leas tone that I know of & probably more. The one I know of is a 5.0 SEFI powered EB with an NV/Atlas/4.56 combo under it.

As to one under & one over, you may as well go to a 4 link & quit messing with band-aiding leaf springs.
This link is intended to help control the axle w/o the huge design & fab effort of a 4 link, it is nothing close to the end-all, be-all solution to rear suspensions. It is more suited to those who just need a little w/o the overkill & set of compromises that a 4 link requires.