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Discussion Starter · #1 · (Edited)
So here I am now after having my Olds rear narrowed and the perches flipped and I want to run a set of ladder bars. I've read all about the problems with running things solid but to run the "floater kit" would basically wipe out all my brake lines and the whole disc mounting point that's all been done already, torch another set of perches off and have to have it checked or straightened again before mocking up my ladder bars.

I've read some about shackling the front of the ladder bars with a short shackle to give it just enough movement but not allow it to wrap the axle.
Any info out there or ideas?
 

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A double heim link would work

If you are going mostly for looks and not crazy fast 1/4 mile times (about 12.00 or slower) you could do a double heim end front link on a long ladder bar. You would still get housing rotation control, and would eliminate much of the bind of having a ridgid eye mount. You would not get all of the location and tuning benefits of a fixed ladder bar, but it will at least control leaf spring wrap up.

Driver.
 

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Discussion Starter · #3 ·
I will be running a 50'' ladder bar and I'm building the car to just drive with the occasional trip down a strip just to see what she can do. so that's sounds like a good option 57driver, any others? thanks guys
 

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So here I am now after having my Olds rear narrowed and the perches flipped and I want to run a set of ladder bars. I've read all about the problems with running things solid but to run the "floater kit" would basically wipe out all my brake lines and the whole disc mounting point that's all been done already, torch another set of perches off and have to have it checked or straightened again before mocking up my ladder bars.

I've read some about shackling the front of the ladder bars with a short shackle to give it just enough movement but not allow it to wrap the axle.
Any info out there or ideas?
Many years ago I flipped the perches and had ladder bars.

My only advice is to be sure you understand the rules of pinion angle before you weld your perches.
 

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Discussion Starter · #5 ·
the pinion angle was moved 5 degrees to account for the flip. I had a shop do all the work to the rear. they have set them up before, that stuff is a little out of my league of knowledge. but thanks
 

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If you are going mostly for looks and not crazy fast 1/4 mile times (about 12.00 or slower) you could do a double heim end front link on a long ladder bar. You would still get housing rotation control, and would eliminate much of the bind of having a ridgid eye mount. You would not get all of the location and tuning benefits of a fixed ladder bar, but it will at least control leaf spring wrap up.

Driver.
Ever who made that drawing is a real deal shade tree engineer! :sign0020:
 

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you will still will have to have your housing straightened after welding on the ladder bar mounts. heat distorts. you can machine the pin hole in the perch into a slot and fab the rest of the slider yourself and still use all the brakes and everything else. slider install doesn't affect the brake install. just make a couple of lines. cost 14 bucks.
 

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Drawing from another member

Ever who made that drawing is a real deal shade tree engineer! :sign0020:
Wasn't that one of your old drawings that I added notations to?? I had that sketch lying around from another post that I responded to a long time ago, and just recycled it here because the topic was similar. Sometimes firing up Autocad and doing a dimensional print is a little excessive to communicate a simple concept. You should see what kind of outstanding design work I can do when you hand me a box of Crayolas...

Driver.
 

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Discussion Starter · #9 ·
hotrod726, problem is my brake lines and perches for them are already drilled and welded onto the housing, it would be a lot of work to redo that at this point. and yes it will need to be straightened, that's why the perches are tacked right now, I'm doing that lovely job of scraping undercoating off my floors so I can paint them and get the body back on the frame for ladder bar mockup, then tack those and take it back to the shop for full welding and straightening. I'm a certified welder but I don't have the jig or straightening setup they do so I just hand over that green stuff and say thanks.

Anyhow back to my issue, the ladder bars I ordered have a heim joint at the end of them already so I was looking at the double heim joint setup that 57driver has there but im afraid it wont work without deleting the heim joint and blasting off the powdercoating to weld on two flanges for a joint to go into. Anyone else has any ideas? shackle seems like my only option at this point.
 

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It just seems wrong to do that. I would think that the car would be totally unpredictable at the race track, especially if you have some decent power.

It would probably work on a low power low traction street deal.
 

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Discussion Starter · #11 ·
thats why im trying to find another idea. the shackle thing seems weird but im running out of decent options. my motor was setup to put out 550+ horse
 

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CALTRACS they work on nearly everything.
 

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hotrod726, problem is my brake lines and perches for them are already drilled and welded onto the housing, it would be a lot of work to redo that at this point. and yes it will need to be straightened, that's why the perches are tacked right now, I'm doing that lovely job of scraping undercoating off my floors so I can paint them and get the body back on the frame for ladder bar mockup, then tack those and take it back to the shop for full welding and straightening. I'm a certified welder but I don't have the jig or straightening setup they do so I just hand over that green stuff and say thanks.

Anyhow back to my issue, the ladder bars I ordered have a heim joint at the end of them already so I was looking at the double heim joint setup that 57driver has there but im afraid it wont work without deleting the heim joint and blasting off the powdercoating to weld on two flanges for a joint to go into. Anyone else has any ideas? shackle seems like my only option at this point.
You know for years guys ran ladder bars on the streets without any floating device and survived fine. Maybe this is the time to say "screw it" and just fix mount them. It would be nice to run the floaters. But if you can't make them fit, then do without. You should be ok.
 

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a little outside of the box thinking:
mount the ladder bars in the "normal" fashion, then put shackles on BOTH ends of the leaf spring. Or sliders on the leafsprings...........
 

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Discussion Starter · #15 ·
You know for years guys ran ladder bars on the streets without any floating device and survived fine. Maybe this is the time to say "screw it" and just fix mount them. It would be nice to run the floaters. But if you can't make them fit, then do without. You should be ok.
you know i'm starting to think this way too. with the talk of grooving out the hole for the pin on the springs i think i may just oval the holes for the front of the ladder bar and call it good. decent movement from that and still have the solid(ish) mounting. HOTROD the caltracs wont work with my flipped perches and outside the box is also a good idea CLASSIC GARY but shackling the front would put me even farther up in the rear. need to get the body set back down and see where it sits, thanks guys, lots of good ideas
 

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you know i'm starting to think this way too. with the talk of grooving out the hole for the pin on the springs i think i may just oval the holes for the front of the ladder bar and call it good. decent movement from that and still have the solid(ish) mounting. HOTROD the caltracs wont work with my flipped perches and outside the box is also a good idea CLASSIC GARY but shackling the front would put me even farther up in the rear. need to get the body set back down and see where it sits, thanks guys, lots of good ideas
use SLIDERS instead of shackles
 

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The sliders replace the hard mount where the center bolt in the spring positively located in a hole in the spring perch. You'll still need shackles at the rear, or another slider back there.

Another way to do this, it's common on torque arm mounts, is to put a slider at the front of the torque arm or ladder bar.

The biggest thing about not having something, mounting it all hard, is not breaking things, but just the fact that without something that allows some movement (either sliding or just a big soft bushing), you're going to have binding. I.e., it's going to act like a solid mounted axle. And that will negate the tire planting effect of the ladder bar.
 

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Binding with two different length suspension "arms"

The biggest thing about not having something, mounting it all hard, is not breaking things, but just the fact that without something that allows some movement (either sliding or just a big soft bushing), you're going to have binding. I.e., it's going to act like a solid mounted axle. And that will negate the tire planting effect of the ladder bar.
Look at the drawing below to see what Rick is talking about. The leaf spring (green arc), from the center of the front eye, to the center of the axle is one "ladder bar" or a fixed suspension link. For now, temporarily ignore the rear part of the leaf spring, from the center line of the axle back, as it does not influence the arc geometry in this discussion. The ladder bar (red arc) is the longer, stronger fixed suspension link. Both links want to travel on separate arcs which means two things:

1. It is impossible to change the center to center distance of either of the two members (spring or ladder) as the suspension travels. The arcs only intersect at a single point, and suspension travel either up or down from this point of convergence/intersect results in a severe "linear" bind.
2. The two members also rotate at different rates (degrees per inch of linear travel) causing "angular" bind.

As a practical matter, the angular bind is not as severe as the linear bind per inch of suspension travel, which is why I did not address it in my first post about doing double rod ends at the front of a "cosmetic" ladder bar. Despite the fact that it is less severe than the linear component of bind, it is still present. That is why a housing floater allows the housing to rotate, as well as slide.

In real world use, the leaf spring can absorb a fair amount of this bind, up to a point. The suspension still travels some, but it is becomes very stiff after traveling a short distance, as the bind increases. If you load the suspension very heavily (like on a very hard launch on slicks) something eventually breaks. I have personally torn apart 3/4" 20,000lb rated rod ends on a 4-link, because of having the suspension in bind. Because of the multiplication effect of leverage, the local forces encountered in a severe bind condition are in the tens of thousands of pounds, not just a couple of hundred lbs like you might expect.

Independent of poor ride quality, and the risk of breakage, a proper drag race suspension cannot be tuned when in bind. Very small amounts of pre-load on a single side are acceptable in certain applications where the car refuses to launch straight on a non-preloaded suspension, but geometric freedom of movement is vital.

It is absolutely true that many "old school" suspensions were ad hoc designs operating in a bind condition, done by hot rodders and fabricators that were not aware of many of the fixed rules of proper suspension design. This doesn't mean that the cars did not hook or did not go fast. It does mean that they would have worked a lot better and gone faster if they did not make fundamental mistakes in design.

Bottom line is that you can violate some of the rules in proper design, the first being that a given geometry must not bind under any of the expected operating conditions, but the risk of failure increases with the severity of service, i.e. high HP racing. Even when trying to adhere to the "old school" look, it is never advisable to intentionally build bind into a suspension. You can have free travel without compromising the look, even if it means cutting stuff up and re-doing it. Yes, it bites, but I stopped counting the amount of times that I cut stuff back up after thinking I could move on to the next step in a build.

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What does spring wrap indicate?

does spring wrap fall into the definition of binding? (traditional pinion angle change w/o traction bars). lol. i figure ladder bars are all about weight transfer for traction
Spring wrap under acceleration means that the suspension is probably not in a bind condition, and it would also mean that any installed ladder bar is not fixed completely to the housing. Spring wrap is from housing rotation, of course, and a traditional ladder bar allows Zero housing rotation. In a proper ladder bar installation, the spring and the bar do two separate, unrelated jobs:

1. The ladder bar locates the axle front to back, and rotationally to establish pinion angle.
2. The leaf spring supports only the weight of the car. It does nothing to keep the axle located front to back, and does not preserve pinion angle.

You should include some photos of your trailing arm setup on your 55. I seem to remember about a year ago you posting about going to a trailing arm which a lot of us questioned, until you made it clear that they were heavily reinforced truck style arms that would never bend in the center of the arm. A very long arm like yours gives a good long instant center, which can be good for traction, and actually allows the car to wheelie a little easier. I don't recall what you did for springs, but some of your concepts might apply to what GTO is doing.

Driver.
 
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