Hey chassis boys... 1.5 degree difference in king pin inclination left to right?

[Dirt-T]

Lee gave me inspiration for front shocks. Here is how I am doing mine.
The spring perches are made out of 1" Dom 1/8" wall. The bushings I purchased fro Pete & Jakes .
The shock mount (Axel) are 1 1/4 " 3/16 thick.
The top shock will be a Lee type , once I get my short shocks that will determine high.

 

[Dirt-T]

more pictures.

 

[Lee_in_KC]

Russ, I have wondered about the front panhard bar myself, seems like as the suspension moves up and down the axle will be constantly moving left or right.

In a previous thread I posted my calculations on how much swing would be seen by the axle with the panhard I have... it was slightly less than 1/8". I have driven my car with and without the panhard, and I much prefer it with. It definitely stabilizes the front end during cornering.

 

[Blacksmith54]

As short as your panhard bar is, I would prefer a Watts link instead, but that is just me. My Alignment shop guy tells me no T Bucket type car he has worked on with nearly fifty years experience works well with less than 7 1/2 degrees king pin and nine more often works better. From your picture you have a suicide style tie rod if the spindles were not set to work that way it means the Ackerman angle is backwards because the way Ford originally built them the tie rod was on the back of the axle. and that is what they are talking about reversed axle. Not turning the axle around normally done by swapping the spindles from side to side.

 

[Oldbuilder]

Okay all,,, I know it's Christmas which I am very thankful for,,, no family home so I jumped online and found this post.
Wow this is a good one,,, this part is coming up quickly on my build,,,, I have several questions that need clarification from what I've read,,,
What is Ackermann,,, is there a post about it?
So when you attach the radius rods to the axle mounts ( mine are same as used on a 4 bar setup not welded on) (I have an I-Beam axle),,, then to the frame and finally the spring to the perch,,, there should be no binding or bending occurring,,,, right??? If so I'm in big trouble

When I welded the front spring perch mount on, I set it at 7 degrees with the frame level to the ground. Now that it's on the floor and has most of the weight on it,,, with a mag level,,, it's resting at about 3 degrees. Is that okay???


Lastly,,, looking at the long distance between the center line of the tire to the center line of the spindle on the T that started this post,,, I would think that it would be a major contributing factor to the problem your having. Just my eyeball engineering here. The distance from pivot to where the work is happening should be as close as possible IMHO. I think on the Dodge Magnum they designed the setup to have the centerline of the tire almost on the same plane as the spindle.

Thanks for all the advise. KIS4S please,
GM

 

[EX JUNK]

Ackerman is a principle where the inside front wheel turns at a tighter radius than the outside front wheel in a turn. Ackerman can easily be checked if the tie rod is mounted behind the axle. all you have to do is draw a line through the center of the king pin and through the center of the tie rod mount on both sides and they should intersect at the rear end. However, if you have the tie rod mounted in front of the axle and you have stock steering arm the lines will NEVER intersect and you'll have reversed Ackerman. This will cause a harder steering with scuffing of the tread. It can only be corrected with new, properly built steering arms. There are some guys that feel that Ackerman is not important but it is if you are concerned about having a PROPERLY built car. IMHO

Jim

 

[bobs66440]

Yes, otherwise the tires would be scrubbing in a turn. Here's a pretty simple explanation video...

 

[roadmonster]

Not clear from the photo, but are you running radius rods with a tube axle? Both So-Cal and Speedway strongly advise against this because the tube can't flex like an I-beam. 4-link should be fine but can't see from photo. A long springy drag link will also cause a death wobble. Reverse Ackerman and toe-out will make everything worse.

 

[EX JUNK]

Not clear from the photo, but are you running radius rods with a tube axle? Both So-Cal and Speedway strongly advise against this because the tube can't flex like an I-beam. 4-link should be fine but can't see from photo. A long springy drag link will also cause a death wobble. Reverse Ackerman and toe-out will make everything worse.

I think that you mean four BAR, a four LINK is different and the terms are not interchangeable. Four bar suspension is best for a tube front axle.

Jim

 

[baddawgcustoms]

Not clear from the photo, but are you running radius rods with a tube axle? Both So-Cal and Speedway strongly advise against this because the tube can't flex like an I-beam. 4-link should be fine but can't see from photo. A long springy drag link will also cause a death wobble. Reverse Ackerman and toe-out will make everything worse.

If they advise against it, they sure don't hesitate to sell a kit with tube axle and radius rods, and so does everyone else in the business. That's one of speedways best sellers in the picture, but yes four bar is always a better setup because there is no bind. Not disagreeing with you at all, because it IS true that tubes with radius rods are put in a bind when one side travels and the other doesn't. It's not the perfect setup, but very widely used.

 

[Hackerbilt]

If they advise against it, they sure don't hesitate to sell a kit with tube axle and radius rods, and so does everyone else in the business. That's one of speedways best sellers in the picture, but yes four bar is always a better setup because there is no bind. Not disagreeing with you at all, because it IS true that tubes with radius rods are put in a bind when one side travels and the other doesn't. It's not the perfect setup, but very widely used.

I think a T is so light that it hardly matters from a stress standpoint. The car will simply lift a wheel if it gets to a bind point, whereas a heavier car might force the stress beyond the ability of the various parts to accept it and something will break!
Still not really a good thing...but being lighter makes it a little less critical.

 

[bobs66440]

I think a T is so light that it hardly matters from a stress standpoint. The car will simply lift a wheel if it gets to a bind point, whereas a heavier car might force the stress beyond the ability of the various parts to accept it and something will break!
Still not really a good thing...but being lighter makes it a little less critical.

After reading this topic I was very confused. I am a novice at building T's, so I had never heard of the binding issue. But I too noticed that most if not all the respected suppliers/builders of kits use the tube axle/hairpin setup. Why would all these suppliers provide such a design if it were so inherently dangerous? Why not eliminate the design and make 4-bar the standard? I did a little more digging and found a heated thread on the H.A.M.B. (http://www.jalopyjournal.com/forum/showthread.php?t=280835&showall=1) regarding this. Half were basically saying that the setup has been around since the early days of the Kurtis midgets and on countless race cars, T buckets and hot rods since the beginning of time and no one can provide any real information regarding failure. The other half provided the warning that if you run it that way, you are driving a ticking time bomb that will certainly fail. Of course this had me worried since I'm using the same setup. So I went out into the garage and jacked up one wheel to see what would happen. The tire I was jacking was more than 6" off the ground before the other tire came up. And as far as I can tell, it was really the rigidity of the front spring that was pulling the other tire up, not binding. Certainly plenty of inherent flex built in regardless. It would seem to me that if it were a significant amount of binding, the chassis would be much more rigid than that. Just for the heck of it, I tried it on the rear also, but removed the coil-over springs to eliminate any interference with binding. The tire was about 3" off the floor before the chassis moved vertically at all. And when the shock finally bottomed out there was about 1" of vertical chassis movement, but I could still easily wiggle the radius rods. So as far as I could tell, there is no significant binding at all. This is all certainly not a exact scientific test, but I think it shows something...

Like Hackerbilt said, there are many factors involved. The car's weight, design geometry, etc. all have an effect. And from what I can gather, the split wishbone is worse than the hairpin because there is little flex in those.

I have no doubt that a 4-bar setup is better. I guess it's just a matter of degrees. It's not just about breakage, but also about handling and proper geometry. If you are building a rock crawler, this setup probably isn't what you want. But for a T bucket that has maybe 2" of suspension travel, apparently it's satisfactory if designed properly.

 

[Hackerbilt]

If you are building a rock crawler, this setup probably isn't what you want. But for a T bucket that has maybe 2" of suspension travel, apparently it's satisfactory if designed properly.

Theres never gonna be agreement on it because there are too many variables to factor in.
It's important to keep the potential for a problem in the back of your mind and test accordingly, as you just did. So many different configurations are possible that nothing should be just taken for granted.
Stuff has broken...similar stuff has survived.

Your last thought sums it up quite well I think!

 

[baddawgcustoms]

After reading this topic I was very confused. I am a novice at building T's, so I had never heard of the binding issue. But I too noticed that most if not all the respected suppliers/builders of kits use the tube axle/hairpin setup. Why would all these suppliers provide such a design if it were so inherently dangerous? Why not eliminate the design and make 4-bar the standard? I did a little more digging and found a heated thread on the H.A.M.B. (http://www.jalopyjournal.com/forum/showthread.php?t=280835&showall=1) regarding this. Half were basically saying that the setup has been around since the early days of the Kurtis midgets and on countless race cars, T buckets and hot rods since the beginning of time and no one can provide any real information regarding failure. The other half provided the warning that if you run it that way, you are driving a ticking time bomb that will certainly fail. Of course this had me worried since I'm using the same setup. So I went out into the garage and jacked up one wheel to see what would happen. The tire I was jacking was more than 6" off the ground before the other tire came up. And as far as I can tell, it was really the rigidity of the front spring that was pulling the other tire up, not binding. Certainly plenty of inherent flex built in regardless. It would seem to me that if it were a significant amount of binding, the chassis would be much more rigid than that. Just for the heck of it, I tried it on the rear also, but removed the coil-over springs to eliminate any interference with binding. The tire was about 3" off the floor before the chassis moved vertically at all. And when the shock finally bottomed out there was about 1" of vertical chassis movement, but I could still easily wiggle the radius rods. So as far as I could tell, there is no significant binding at all. This is all certainly not a exact scientific test, but I think it shows something...

Like Hackerbilt said, there are many factors involved. The car's weight, design geometry, etc. all have an effect. And from what I can gather, the split wishbone is worse than the hairpin because there is little flex in those.

I have no doubt that a 4-bar setup is better. I guess it's just a matter of degrees. It's not just about breakage, but also about handling and proper geometry. If you are building a rock crawler, this setup probably isn't what you want. But for a T bucket that has maybe 2" of suspension travel, apparently it's satisfactory if designed properly.

Bob I read all the warnings myself and read a lot about the tube axle with hairpins. I spoke to a guy that i really learned to trust because of his obvious knowledge on chassis engineering. As he explained to me the longer your rods the less caster change there is. 27" seems to be standard. At that length there is hardly any change enough to "twist" anything. He did the math and I believe it was 1/2 degree caster change at 2 inches of travel. I'm using the same setup as you but I had Ron at RPM make my hairpins 40" long just for good measure. And I just like the look of the long hairpins. I am interested to get them bolted on and jack one side up just to check the caster change but I ain't sweatin it. Think of all the radius rod type setups on rear ends and there is no flex on them!