Autofab Racecars - Street Rod Ladder Bars

[brink_79camaro]

I am in the process of putting some Autofab Racecars street rod ladder bars in my Camaro as well as some new formed rear frame rails and a Ford 9" rearend. I was wondering if anyone has used these ladder bars and what kind of result they got. I have single adjustable QA1 coilovers to complete the setup. I am using this setup because they are designed to keep the rear seat and does not require any cutting to the rear floor pans. The link is posted below for the ladder bars.

http://www.autofabracecars.com/chassis_suspension.htm

[David Pozzi]

Is this for a drag-only car?
They aren't going to work for going around corners.
David

[brink_79camaro]

I am mainly going to drive the car on the street on weekend cruises and car shows. I eventually would like to run the car at the strip every once in a while. The coilovers will be located about 3-4 inches farther inboard I believe than the stock shocks.

[silver69camaro]

There isn't a whole lot to ladder bars, the SVSA length is pretty much the only thing that most people are concerned width. Longer is better for a street car, but IMO, this is the wrong forum for that. Ladder bars are a big no-no around here.

[1971novaSS]

I Decided to go with ladder bars for the same reason that you are. KEEPING my stock rear seat. But i have done a few things to create more street "flex". And i might be running a rear sway bar as well.

I will be posting again on this subject when i take it out for a trial run in about a month or less.

https://static1.pt-content.com/images/pt/2007/03/100_0827-1.jpg

[Goatman]

They are designed for straight line traction. The good ones make you cut through the floor because that's where they need to be for your instant center mods. "Street" ladder bars, there are no such thing. Just ones that bolt up without cutting, and probably don't have hiem joints either.


They'll be a real PIA on the street most likely.

[silver69camaro]

"But i have done a few things to create more street "flex". And i might be running a rear sway bar as well. "

Whoa, put on the brakes here. Let's get back to basics.

First, imagine the ladder bars bolted to the frame and axle. Now, imagine what happens when you twist the axle about the middle. See the bind?

This is not good for two reasons:
1. When stuff binds like this, something will break. I don't care if you use poly rod ends, rubber, etc...doesn't matter. It will break. Rarely people put enough miles on the car to really worry about it, but it has happened.

2. By the nature of design, it is NOT ment to turn corners. I don't implying you want to keep up with Ferraris, but I mean general street driving. Sure, poly rod ends help, but it's technically wrong. I will never design a suspension that relies on the deformation of links to promote axle articulation.

3. Adding a sway bar implies you want to turn corners. Also, a sway bar can increase the roll rate to the point where a snap oversteer condition exists. Not good!

I design chassis for the better part of my day, and from experience, the worst thing a person can do is build the car around their back seat. It creates a heard of problems, and the project would be mechanically better if a little more work were done. In your case, you can do many things with the rear suspension and still keep the seat.

[1971novaSS]

I know exactly where the bind is. I am a civil engineering major. Im sure i know what kind of tolerance and forces are being exherted due to flex in the rear end from road conditions.

I will take your criticism with a smile. :geek:

And to imply that i need to do more work on my car is wrong of you. You have no idea how much work i have done to my car.

I am not building the car around a seat... Please.....:rolleyes: Just simply would like to keep the stock seat. I have mini-tubbed the car and have already modified the seat to the mini-tub. I also have channels cut into the floor boards for clearence of the ladder bars as well, which the seat has yet again been modified for.

If they are not up to the standard that i believe they will be then im out.... What..... 300 bucks for a set of ladder bars? Thats pennies, as you all know from building a car.

But thanks for the concern and information.

[silver69camaro]

Nova,
Nowhere did I say or imply that you haven't done enough work on the car. I wouldn't ever say that, like you said, it would be wrong. We all know what it can take to build these things. That would be silly.

You said you want to use ladder bars to keep the rear seat, and this is not, in my professional opinion, a good idea. There are better ways around this. Sure, you aren't building the entire car around the back seat, but putting in a seat of ladder bars will dramatically change the way the car behaves...and you are building the rear suspension around the back seat. But even so, you can use a triangulated 4-bar from many of the companies that offer bolt-in kits for your car. Or, for drag racing, Cal-Tracs and leafs work extremely well.

In the end, only you know how you will use your car. I just get worried about ladder bars because I see this every day; this is what I do for a living.

[1971novaSS]

and the project would be mechanically better if a little more work were done

I might have taken this the wrong way then. Had a lack of sleep due to work and college. Im sure you understand...

And i started the ladder bar idea when i was in the middle of a heated debate between ladder bars and 4-links. I might have listened to the wrong person who suggested ladder bars.

What do you think about modifying my ladder bars to create a 3-bar system...? In your professional experience...

This is my idea- Perhaps eliminate both of the Top links that connects to the rear end(while strengthening bottom links with extra metal, Ultimatly deleting the bind due to the flex-rotation created when the body-roll is created from cornering. Then putting in a crossmember that has the third/top link to the rear-end. I havn't not thought to much about the physics of this setup much. But perhaps will give me the desired "locomotion" the rear end will need.

I had originally calculated for 4 total inches of body flex on top of the rear end. IE: When cornering the car will drop two inches on the outside of the corner due to centrifugal force. And on the reverse side(side facing the corner) it will raise approximently 2 inches. Creating a 4 inche overall flex of the body. I have basically a customized flexible eyebolt that will allow for this amount of flex. I am now starting to dought my calculations and assesments of the situation in which the rearend will under-go.


Also, a sway bar can increase the roll rate to the point where a snap oversteer condition exists. Not good!

I had the impression that the mechanics of the sway bar reduces the amount of unequal Body roll. Connecting the rear-end with bushings and the frame rail with bushings. Did i get the wrong information?

Thanks for the time to talk about this subject 69camaro. I am always in quest for new information... And different opinions, Two brains are way better then one.

P.S.- I am located in the Tri-Cities, WA

[Derek69SS]

Ladder bars give you a theoretic infinite roll-stiffness. The only way the rear axle can articulate is if something is bending (arms, axle housing, or brackets)

Stabilizer bars are effectively a spring that increases roll stiffness.

You already have too much rear roll stiffness with your ladder bars, so a sway bar in the rear is only going to make it worse.

Too much roll stiffness in the rear creates oversteer, too little creates understeer.

[MonzaRacer]

Instead of ladders I would have called Jegs and ordered a set of Jegster SS bars. Remove one bolt from one ofr the links and it becomes a "3 limk" rather than a ladder bar setup, but the bolt back in and they work as ladders.
Good luck
Lee

[1971novaSS]

And i do have articulation with the ladder bars that i have due to the modifications i have made. But i dont believe they are enough for the torture i am going to put on them

I will be creating a 3-link. Which i have researched for a few hours today and is supposed to be one heck of a performing rear suspension.

So that is what i am fabricating.

[Goatman]

Still won't be optimal or comfortable, but it will be better that way...

[silver69camaro]

No harm done, Nova. I understand how it is, I've been there..

I agree, remove the top link to essentially have two lower links, and build a top one. The lower links may be a tad short (don't know how long your ladder bars are), but workable. I think it would be very interesting.

Derek pretty much explained the issue of roll bind.

[1971novaSS]

Here is a few people talking about the 3-link suspesion on PHR.

http://forums.popularhotrodding.com/70/1004151/hot-rod-technical-articles/three-link-suspension/index.ht

Another artical on the 3-link suspension. There are some really good reviews and information about this suspension. Seems to be a really good handling suspension.

http://www.crankshaftcoalition.com/wiki/Suspension

3-Link suspension is a design of rear suspension which has 3 control arms on a solid rear axle connecting it to the body. The two bottom links remain in the their typical location while the top 3rd link is attached to the top of the rear end perfectly center. It is said this type of setup achieves the best handling as the rear end is allowed to tilt from side to side with the roadway, while the rear end is kept centered. This setup must utilize either a Panhard bar or Watt's link for centering the rear axle. The one main disadvantage of this setup is when retrofitting it on old cars the back seat may have to be removed entirely to allow the 3rd control arm to be attached to the body optimally. Coil springs and shocks are used in this setup or a coil-over setup can be used


Here is some info on the FFR 3-link. A very well thought out system used strictly for professional rally racing in well build cars(not hondas)
http://www.factoryfive.com/table/newsltr/newsltr02/threelink.html


I have a question For 69silvercamao... What do you think about the watts link. It is supposed to be superior to a panhard bar from what i have read so far... How does it work? How to set it up?

Oh, and my ladder bars currently are 32 inches. So the bottom links will be 32 inches as well. I will be re-inforceing the bottom two links with an extra steel tubing welded to original tubing(lower link).

Here is the basic design that i will be using. My lower links are much longer that this persons setup. I will be using eye-bolt attachments instead of the bushings, For better ability to accept articulation of the rear-end. His upper link has two connecting points to the frame, Im thinking about just going with one?.... Here are some of the pics of his suspension.

https://static1.pt-content.com/images/pt/2007/03/11538166420-1.jpg

https://static1.pt-content.com/images/pt/2007/03/11538172860-1.jpg

[Derek69SS]

That setup isn't too bad, but the RCH is very high. Also, some sort of spherical bearing should be used on the axle end of all 3 arms to reduce roll bind. Those look like poly (?) which is worse than rubber in this case.

I would also move both frame-side points on the upper arm to distribute the load on the crossmember more evenly. It looks like he was forced to offset it for fuel tank clearance.

'58 Impalas had a setup kind of like that, and I've heard some newer Jeeps do too.

[silver69camaro]

I'm not sure about that design. That upper link acts more like a wishbone locator rather than a link...it will bind up. There should just be one point of connection to the frame, not two. And it's tough to tell by the photo, but the LCA angle is high (down from parallel). Anti-squat seems as if it would be very low.

This is the way I designed ours:
http://www.artmorrison.com/2006cat/25.pdf

[Beige]

As far as minitrucks go, I'm suprised to see as much thought put into a suspension as that. It's scary to see what passes as a suspension on some of them.