Correct shackle angle & other ?s

[Caver Dave]

Well, despite working about 100 hours over the past week & a half... the Moss will not be making URE this weekend! I had got off work early yesterday, flew home and started on finishing her up for the weekend. TR/DL went back in, fluids topped off, battery charged, etc... all that was left is to load all my tools, spares, & fluids in the back!
So I backed her into the backyard to get the truck/trailer out of the fence... I noticed on small side hill the drivers side leaf didn't seem to compress far (tire was FAR from hitting the fender....), so when I took a peek, it was obvious. Both shackles had inverted up against the frame (couldn't swing any farther) and the leafs were in a slight bind (as evidenced by the leaf bent into a wavy line )
... at almost 9PM, it was a bit late to booty fab the shackles or move the rear hanger point... NO steel (other than sheetmetal) in the cupboard, NO wire for the MIG, TSC was closed, & the Lowe's near my house doesn't even carry MIG wire Plus there's no way I'm gonna run them like this and either fawk the packs or rip the hangers off on the trail...
Here are some of the particulars...
- Swapped in Downey 3" Toy rears onto the front
- RE perches were set into the front holes (to locate the axle in relatively the stock location, but ended up being 1" forward)
- stock "waggy" type shackles
- sitting static, the shackles are at a 30* angle from the frame (what *should they be at?)
Seems I could either:
a) move the shackle hangers forward (PITA since the PO welded them to the frame)
b) plate some addt'l length onto the exist shackles
c) plate the rear hangers, so I can move the rear eye aft... effectively making the existing shackles/hanger work *AND* moving my axle back to the stock location
"C" being the quickest/simplest way to get everything back where it needs to be & free swinging

 

[mbalbritton]

Looking at angles, I wouldn't want to see any less thana 20º

here's a quick drawing of 20º, 30º and 45º.

 

[mbalbritton]

Oh, and Option C as I said last night when you called cryin in your wheaties....

How much meat is there in the Spring hanger? enough to redrill a hole about 3/4" behind the existing?????

 

[Rich]

How long are your shackles, eye-to-eye, right now? If they are short, you can try a longer shackle, but I like to keep 'em no longer than 5", eye to eye.

Otherwise, measure how long your springs are when flat, and go from that point, using a fake shackle at a 45-50° angle, and you'll see exactly where the shackle hangar needs to go.

I can't tell you what your shackle should sit at when at rest, since it's totally dependant on how arched the springs are at rest.

Oh, by the way, the ° measurements I refer to are from VERTICAL, not from the frame.

 

[spraypaintman]

My shackles are laid back pretty far too. They stop at certain point and then the springs go into negative arch. Are your springs flat enough to do this? Maybe you don't need to move the hanger....

 

[drkelly]

How long are your shackles, eye-to-eye, right now? If they are short, you can try a longer shackle, but I like to keep 'em no longer than 5", eye to eye.

I am curious as to what your thoughts are on why no longer than 5". John and I had some in depth discussion on this, and I think the required shackle length is proportional to the length of the spring and the distance the springs are mounted apart. My stock ones were about 4.5", and I ended up extending them to 9". My reasoning behind it was that I had a really long spring (64" Chevy's) mounted far apart outboard of the frame. The side under droop was going to really shorten up eye to eye while the other side stuffed. In the picture you can see the angle I ended up deciding on. It seems to have worked out about as planned. When flexed out the shackle goes about perpendicular to the frame and appears safe from going into toggle and flipping forward. On the flip side, I did the measurements before positioning the hanger to make sure the stuffed side would not completely flatten out the shackle and bend the leaf.

 

[Rich]

Good point.. I was referring to the shorter springs we run that are usually shorter than 50" long.. Keeping them shorter does halp with sidehilling though, keeps the axle from really shifting side to side.

For reference, stock cruiser ones are something around 2.5 or 3".

Mine are closer to 6" long honestly, but I would prefer 'em a little shorter.

End result is you're absolutely right.. a long spring that will see a larger length change between droop length and flat length will require a longer shackle to accomodate it.. good point!

 

[ncjeepinyj]

Would a boomerang shackle either help or solve your problem?

 

[wbcarver]

Would a boomerang shackle either help or solve your problem?

Nope -

A boomerang shackle helps to clear obstructions, it DOES NOT make ANY difference in suspension geometry.
Mounting points and shackle length will make a difference, but not the shape of the shackle.

The suspension only "Sees" the angle between point "A" and point "B", it does not care how it gets there.

The same is true for steering draglinks, and the question comes up all the time.

I created an animated diagram to (hopefully) illustrate the concept.
I hope this is a case of a picture being worth 1000 words.

 

[Caver Dave]

How long are your shackles, eye-to-eye, right now? If they are short, you can try a longer shackle, but I like to keep 'em no longer than 5", eye to eye.

They are exactly 3" eye-to-eye

Otherwise, measure how long your springs are when flat,

They appear to be about 1" longer than the existing shackles allow them to move

Oh, by the way, the ° measurements I refer to are from VERTICAL, not from the frame.

In that case, I believe I'm looking at 60* (from vertical)... about 20 more positions closer to the frame than Brent's drawing...
For Brent... crying was sure better than slepping around the house all weekend!
I agree with Bill on the boomarang shackles... unless they're longer, it will do nothing for me.
Now, back to my "plan C"... since the axle ended up further forward than I would have liked (*WILL* create all kinds of fender/grill/bumper contact issues... simply lengthening the shackles will only let it swing further forward, compounding the ill placement... correct?
I should be able to simply plate the existing hangers to allow me to move the fixed end rearward enough to "stand up" the shackles? As it is now, the hangers taper on both side to the holes, so no way to simply redrill rearward (I heard from several folks this is a common process for Zuki folks running CJ/YJ leafs?). This will resolve both the shackle length issue *AND* move the axle aft by another 1"-1.5" (back to stock location) to negate clearance issues... correct?

 

[Rich]

I believe I'm looking at 60* (from vertical)... about 20 more positions closer to the frame than Brent's drawing...

Take a picture or 3 (including a shot from under showing how the whole leaf sits).. you mean the shackle is pointing towards the ground forward, and not towards the rear like it should? You've got big problems in that case.

By all means, move the fixed end back, but I have a feeling your shackle angle still won't be right even if you move the fixed and back 1.5"...

Still might need longer shackles too.

You mentioned "Grille".. so this is a front axle, with a rear-mounted shackle? don't forget that a longer shackle will lower your pinion and increase caster.

 

[Caver Dave]

I'll snap a few digi's this evening, but in the meantime to clarify...

- it is the front axle
- OEM shackles to the front
- the shackle is pointing forward about 30* from the frame (or 60* from vertical)
- when compressing, the leaf is flattening, decreasing the 30* angle to 0*, & locking against the frame (the shackle hangers sit 6" aft of the front edge of the frame)
- shackles are definitely too short as the springs are kinked/wavy (very slightly) when pegged against the frame
- Swapping/modding the shackles is uber simple, but I'm afraid that would compound clearance issues

I've looked it over and believe moving the fixed point rearward in relation to the shackles will be fine, but want to make sure there's not a hidden gotcha.... as you pointed out, may take a combo of moving the fixed end back *AND* lengthening the shackles????

 

[Rich]

Do you have enough slip in your driveshaft to move the axle back 1.5" and not over-compress it?

Now I'm following you... You might be OK just moving the fixed end back. Not knowing how far the shackle moves when drooped though, can't tell if longer shackles will be needed.

ex: if right now, at full droop, your shackle moves through 60° of arc and stands straight up, if you change the static angle to 30° (forward), at full droop, it will now pull to 30° (rearwards), which doesn't give me a warm fuzzy.

One question.. how arched are the springs at rest?

 

[Caver Dave]

Do you have enough slip in your driveshaft to move the axle back 1.5" and not over-compress it?

I think so since 1.5" aft would put it back where it's been for the past 5 years...

One question.. how arched are the springs at rest?

Loose on the floor? Pretty well arched... I don't have a measurement for them, but do have a comparison pic and can measure the old leafs for reference...

Under the Jeep?... appears to have about 2"-2.5" before they'd go flat...

 

[Caver Dave]

For comparison, the old leafs are 8.5" floor to highest point...

Shackle angle... they were against the frame and had "locked" themselves there... took lifting it approx. 5" of lift w/ the HiLift for them to fall away

Hanger...

 

[Caver Dave]

Static...

 

[ncjeepinyj]

Nope -
A boomerang shackle helps to clear obstructions, it DOES NOT make ANY difference in suspension geometry.
Mounting points and shackle length will make a difference, but not the shape of the shackle.
The suspension only "Sees" the angle between point "A" and point "B", it does not care how it gets there.
The same is true for steering draglinks, and the question comes up all the time.
I created an animated diagram to (hopefully) illustrate the concept.
I hope this is a case of a picture being worth 1000 words.

Got it. Think i misunderstood the problem originally but after seeing the new pics and your diagram i see how that wouldnt help.

 

[Rich]

I'm gonna shoot a WAG here, but it looks like if you move the spring back the 1.5", and run a 1" longer shackle, you might just be in the money, assuming you can afford to lose a little caster...

 

[uglyjeepoffroad]

FWIW, Mine are nowhere near the angle yours are at rest. I 3rd or 4th the moving the rear back idea.

 

[Caver Dave]

I'm gonna shoot a WAG here, but it looks like if you move the spring back the 1.5", and run a 1" longer shackle, you might just be in the money, assuming you can afford to lose a little caster...

That's what I was thinking all along Rich. Grabbed some wire, cut-offs, and short sections of 3/16" & 1/4" last night on the way in, but didn't get anything done other than the pics posted...

Next question.... I had planned to simply plate over the outside of the hanger, but that would put the holes (1.5" back) directly on the lap. What's the thoughts of beveling & butt welding the scabs on? That will let me smooth where the holes need to go... so the bushings don't get chewed up/bind

 

[mbalbritton]

Dammit Dave... Cut the side welds and grind that damn Rivet out. Jerk the Spring mounts off. Wire wheel that crusty Rusty frame of yours, move spring mounts back 1.5" and burn them on. Or hell, you're 1/2 way to Shackle reversal if you were ever inclined to do it????

DO NOW!

 

[Yay!Gurrr]

Hell id cut the front shackle mount off and spin that 180 and weld it back on, that will move the mount forward and looks to make it all work out.. ????

 

[spraypaintman]

Hey Dave it looks like your u-bolts are tweaked...you might want to replace those.

 

[Caver Dave]

Or hell, you're 1/2 way to Shackle reversal if you were ever inclined to do it????

Sorry, everyone I know that's done that either took 2 years to complete it (and some are still PARKED) and I plan to actually wheel mine this month!

Hell id cut the front shackle mount off and spin that 180 and weld it back on, that will move the mount forward and looks to make it all work out.. ????

Mike, that would normally work, but will create clearance issues with various front clip sheetmetal...

Hey Dave it looks like your u-bolts are tweaked...you might want to replace those.

Optical delusion bro!

 

[spraypaintman]

Dammit Dave... Cut the side welds and grind that damn Rivet out. Jerk the Spring mounts off. Wire wheel that crusty Rusty frame of yours, move spring mounts back 1.5" and burn them on. Or hell, you're 1/2 way to Shackle reversal if you were ever inclined to do it????

DO NOW!

x2