new shackle idea ? (1 Viewer)

[denis]

Good morning,
I've been searching a lot, and could not find anything about the shackle pivot points relocated up into the frame on non-SR setups. Did I miss something or may this be a new idea ? This should drastically improve the approach and departure angles without sacrifying much flex. A bit of height might be lost but I can definately live with that. I will try it on my '75 anyway but I was curious why this may not have been done before ?

 

[TimCFJ40]

If you had a Saginaw PS box up there you'd have trouble making it work.... Also, your Pinion and Caster angles will be changed. If you're running a stock setup, (as in not cut and turned) it might help you caster angle as I see it, increasing from -1 degree to some larger - number, but hurt your pinion angle. You wouldn't want too much negative caster though. Also with the stock bumber tie in brackets you couldn't do it without "Clearancing" them a little.

I for one would be interested in how it goes.

 

[Brian in Oregon]

Why not just install "Moab Rollers" on the lower end of the shackle?

 

[denis]

Brian, I don't think they are not going to improve my angles in a useful fashion and would be a failure waiting to happen. The most useful thing in the concept, keepin the spring pack safe from obstacles higher than the spring eye will not be achieved with roller. Plus I'm a KISS rather than a gizmo kind of guy.

 

[denis]

Tim, these considerations are a given, thanks. I will post up as soon as I get something done -which may take a while...

 

[Mark W]

Please expond on what you are thinking about. I'm not visualizing/understanding it.


Mark...

 

[denis]

heres what I'm thinking about

 

[Mark W]

Okay, now I see what you're getting at.

This would seriously reduce your shackle travel (forward). Which would call for a longer shackle to allow full spring extension. Which would offest any gain from moving the spring higher. And you would have to either use a shim to correct your caster/pinion angle or you would have to run a long enough shackle to put the spring back where it started.

That's how it looks to me anyway.


Mark...

 

[denis]

Before getting into cutting and welding I would obviously measure and calculate the best pivot location and shackle length for the spring to work at its full potential. The front bumper is going to be reworked a lot to use the design at its best and the axle is going to be butchered (hybridized) down the road anyway.

I'm still curious if anybody seen this done before ?

 

[Mark W]

That doesn't seem to address the problem. If the shackle is limited in its forward travel it will have to be longer. With the shackle in the factory position it can go full flat in the forward direction. That equates to a lot of lateral movement of the shackle end. If you eliminate the upper portion of that arc, you eliminate most of the lateral movement.

If you set the shackle mount upward into the frame, you will have to get the bumper and anything else that normall resides there out of the way.

I don't see any practial way to do it.

Any gain will be minimal in any event.

The front of the spring is not a major clearance problem any way.

I've never been accused of thinking inside the box. But I just don't see it being worth the effort.


Mark...

 

[denis]

I'm not going to eliminate the upper portion of the shackle swing arc. At least I don't want to. The idea is to figure out the fully compressed spring length, put the spring eye as high as it can go, and start from there to get the correct shackle angles and length that would allow for the full travel in the best possible conditions throughout the motion range. The bumper mounting issue will be resolved once the desired geometry is reached. I could go from the bottom of the frame rail inwards of the shackle swing area, out and around the shackle for the lower mounting point of the bumper.

 

[denis]

I've never been accused of thinking inside the box. But I just don't see it being worth the effort.


.

thanks

Any gain is worth some effort, figuring out the geometry is not that huge of an effort and I like to mess with such ideas anyway. I don't want more lift or much more tire right now so I'm trying to push the enevelope as-is.

 

[shelfboy1]

if it was worth all that trouble everyone would already be doing it just go to coils and dont worry about it plus it looks like it will limit spring travel plus lower the truck means frame may hit sooner only advantage i can see is you can say you did it and no 1 else has wonder why good luck either way

 

[Mark W]

Give it a try and report back.


Mark...

 

[denis]

I will take a couple pictures and make measurments once the BJ40 is back in the shop.
After the geometry is figured out it's just a matter of cutting and welding which is not that much trouble. I'll keep the board posted.

 

[fj40forlife]

It would drop your rig a bit

 

[denis]

I figured about 2" at the ends so that would make 1" at the axle. The next round of mods include high-clearance hybrid axles which will put me back to the starting height.
I took a pic of my current shackle arrangements and it looks like the front spring eye on the front pack could be able to travel beyond the bottom corner of the frame. It definately will with just a little cutting so theres a lot to be gained there. On the rear axle not so much unfortunately. We might see.

 

[rabid]

From the look of that last pic, you can try it in the rear without drilling a thing!

Looks like every frame around here.