Projects Misc projects.

Had a couple smaller projects come in I thought I'd share some pictures and info.

Got a '54 Moore door that the owner Jose wanted a 2 link and run coil overs. Things changed and ended up doing ladder bars for him.

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Nice job.

 

Dude.. I'm drinkin. Don't make me tumble... Look's good!

 

Parallel?

 

Thanks

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I'm not sure what's with the pictures they were upright when I selected them.

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Ladder bars.

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Im not used to seeing ladder bars installed parallel.


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Nice ladder bars, just need to learn how to rotate pic's before posting.
You may need a Panhard bar if your bars are parallel!!!

 

Drag only car?

 

It's odd the pictures are right side up on my phone and when I add them in the post but when it posts it's wrong side up.

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It's going a street/ pro street style but not tubing.

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Really? I've never seen not parallel.

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Really? If you have never seen nonparallel ladder bars, then why are you doing suspension work?

I asked about this being a drag-only car for a reason.

Parallel ladder bars will lead to uncontrollable oversteer on the street, when cornering.

Whether or not this causes you to lose control of the vehicle is up to traction, and speed (and NOT driver skill).

Parallel ladder bars turn the bars, and the axle housing into a giant anti-roll-bar. Front suspension body roll will result in the unloading of the inside rear tire in a corner. This will break the rear end lose (oversteer).

This puts immense stress on all of the involved components, which can, and has led to catastrophic failure.

If you are building this car for yourself, you are putting your life at risk.

If you are building this for someone else, and something goes wrong, a cursory accident investigation and reconstruction will put the law, lawyers, and insurance companies at your front door.

Porsche didn't win this lawsuit, and neither will you.

 

It'll be fine. The same concept is used in radius arms on the front of most newer 4wd trucks. Also many front wheel drive cars use a solid tube rear axle with solid links to hold in place. It's the same concept as a common 2 link. Just without the adjustability. I understand your concern. The car will obviously cant be a road race car but will be fine as a street cruiser. I don't see how mounting the arms triangulated would fix your complaint. It would allow the car to go without a panhard bar but it still would be fixed at the rear end offering minimal roll. The only thought would be a wishbone style with a single pivot to fully fulfill your argument. I appreciate your concerns and input.

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Uh, no.

You are wrong on almost all accounts.

 

That's a bit vague. But for your argument to be correct every design of a ladder bar would be leading to failure. If you triangulate them all it does is allow the bars to twist which eventually they will break or the mounts will. Parallel would be the strongest way to set it up. Hence why drag cars are setup that way.

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Triangulated 4 link is a better set up, holds the rear end in place “firmer” for lack of a better word
Less to no side to side movement of the axle
No Panhard bar required


A parallel 4 link is easier to install
Is not as “firm” as a triangulated set up
DOES require a Panhard bar

 

@Kerrynzl @Ned Ludd, either of you should have a look. I am maxed out on work, and don't have time to explain this in deep detail.

 

Not sure why but I think Kerrys account was "adjusted".

 

Uh oh.

 

Drag cars are set up that way because it promotes more even weight transfer, not because of any 'strength' issues. And they're driven on nice flat race tracks in a straight line; any cornering involved is at slow speeds at the beginning and end of runs.

Gimpy is giving you the straight sh!t; that set-up on the street is dangerous. It will have sudden and massive oversteer with little or no warning when you reach the 'limit', swapping ends on you. This is one piece of race-car tech that doesn't transfer to the street worth a damn...

 

His posts are still up and list him as a member, but his profile page seems to be missing.

 

It appears that there is not a lot of suspension travel to the floor pan with that set up. In saying that I had a friend who had a parallel 4-bar installed, by a local rod-shop, to a similar top hat style '46 Chevy frame and it wasn't gusseted sufficiently which I brought it to his attention. It was rectified before the car hit the road, last thing he wanted was a sudden failure at speed.
The top hat frame rails aren't as thick when compared to open 'C' channel or closed channel frames. In addition there were no reinforcing plates where his mounts were welded to the frame. The loads when being driven were not being spread out sufficiently over a larger area and were concentrated at attachment points.
I note that the through tubing is double sheered (Welded both sides) however I envisage that the frame will eventually fail in these areas with stress cracks developing from the forces generated during suspension cycling. The car is being street driven and not 400 yards at a time.
A continuous tube cross-member is inherently stronger. Also I don't see how that setup without a panhard (Locating) bar prevents lateral movement. Rod ends have specific uses are not street car friendly. The adjusters are there to adjust pinion angle and pre-load.

Gimpy and many other HAMBers are extremely knowledgeable when it comes to these critical technical /safety issues and provide sound engineering advise, I personally wouldn't discard their views. Knowledge comes from experience. Suspension dynamics is a science, just ask Art Morrison, Chris Alston and others.

 

It's not done. It will have a track bar. Also it is sitting at lowest point of travel.

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Honestly this is why I don't post on forums often. I've worked on dozens of cars with ladder bars that have no issues. I prefer 4 links myself but the guy that owns the car wanted to buy a 2 link kit and have it installed which was a very poor design. I'm not sure where everyone is trying to go with their lectures. I'm not scrapping the ladder bars. Changing the bars from parallel to triangulate will solve nothing except increase chance of failure. It is a progress picture so it is not done. Yes it will have a track bar or "panhard". If ladder bars are so dangerous why do they exist? Also in design it acts the same way as most any 2 link kit I've ever seen. A solid mount on the axle which would act the exact same way as the ladder bar.

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Gimpys has the principle right, if not the mechanism. What happens is that elastic roll moment loads the outside rear tyre. That is what causes the tendency to oversteer.

Have you ever seen a dump truck being loaded? Have you seen how the rear tyres start to look like they don't have enough air in them, as the load increases? The same thing happens in a car tyre when cornering.

The greater the load on a tyre, the greater the air pressure needed to maintain the tyre's shape. If the tyre loses its shape, it becomes possible for the contact patch at the bottom of the tyre to twist, so it is pointing in a different direction to where the wheel is rolling. The contact patch sits at an angle to the wheel, and that angle is called slip angle. It's not a very good term, because at this stage there isn't any actual slipping happening, but that's what it's called.

Now, we don't have the option of quickly increasing the air pressure in a tyre in real time, nor do I think we'd want to. It's this knack tyres have of running slip angles which makes chassis tunable at all. That is the basis of the central principle of chassis tuning: adding load to the better-performing outside tyre will add grip at the other end of the car.

Let's take a look at what you're doing with your ladder bars. You turn left, so the car rolls right. Relative to the car, the left side of the axle goes down, and the right side comes up. Because the ladder bars are bolted to the axle the way they are, this means that there is now compression in top chord of the left bar and the bottom chord of the right bar, and tension in the bottom chord of the left bar and the top chord of the right bar. What does this do?

Yes, it increases roll stiffness at the back, which will tend to increase oversteer. Though the axle housing is hugely stiff – tell me the diameter, wall thickness, and distance between ladder bar brackets and I'll tell you how stiff – the long ladder bars represent long moment arms and hence a small angle of twist. If that were all there were to it you'd be able to tune that out with a moderately chunky anti-roll bar on the front suspension. But that isn't all there is to it.

Those same long moment arms multiply the forces parallel to the ladder bar chords enormously. Are the fasteners to the axle brackets up to the job? The failure mode I see here is not the entire car going sideways into the woods but either the bolts eating the holes in the axle bracket oval or the axle brackets forging the bolts into little crankshafts. Either way the rear suspension eventually becomes sloppy and unpredictable because everything can move ¼" in its holes and you end up sideways in the woods anyways.

If you beef up the bolts and brackets it just means that something else is going to fail instead. You want to get rid of those tensions and compressions. That's how light truck suspensions are done: plenty of compliance is built in. The downside is rather vague suspension. The other way is to build in some elasticity. Make the ladder bars springy is some way. There are a million ways to do that but you'll have to do it yourself, because the cats are wanting to be fed and I have to go.

 

Thanks Ned.

 

Ladder's, a Pan hard bar, and a FULL cross member..... The RIGHT WAY. That big gap in between those bars is making me a lil nervous.........Not my ass riding in the seat though....... AND, not signing my name on it....
If your's= good luck....... If a customer, well, GOOD LUCK with that too.......
Heed words of wisdom from previous posters....... There's always a way, then there is the correct way......

 

The failure to fail is not the same thing as success.

The fact that you are not sure where everyone is trying to go with their lectures is concerning. Many people commenting here are actual engineers, at actual automobile companies, where they design actual cars. Others are long time racers, chassis designers, and suspension tuners. If that, alone, is not enough for you to gain an understanding of where they are going with the lectures, the failure to understand may be intentional, on your part.

Ladder bars do exist, and they have a place. That place is not on a street vehicle. Just because you have seen them, and the 2-link kits that resemble them, does not make them right, or safe.

I see drug deals frequently. That does not make them right, or safe.

As for mounting two triangulated links, that absolutely does not increase the chance of failure.

Have you ever watched a NASCAR race? Have you seen those cars maintain 200+ mph on a high-banked oval, or road-race course? Have you seen a crash? Go ahead, Google NASCAR crashes. Tell me how many include tearing the rear suspension out.

What do all of those cars have in common? Triangulated 2-link, with flexible links, that can twist.


This is under Kevin Harvick's car. Back-to-back c-channel arms, stagger welded, and rosette welded. Large compliant bushing at the leading-end.