What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Panhard with leaf springs?

Do you guys think the shift would be violent? Like suspension droops, hits limiting strap, and instant shift that could cause sever roll or just make it a little tippy when limited out? I doubt I will run limitng on the front with leaves but of course it will get flexed out, when I go coilovers of course since I want my $1000 to last I'll limit.
 
It's going to be dramatic, but it shouldn't contribute too much to the potential for roll over since the other side is going to (ideally) hit the limit about the same time. The only way I can see it being an issue is if the suspension balance were way out of whack. But in all honesty, I'm talking out of my behind here since I really am no expert and have no experience on this topic. I'm just making observations based on what I think I see as the mechanics involved, and I could easily be wrong.
 
you guys are more knowledgeable than me. I just take what I read here and on pirate and compile it into a my data, if something doesn't match I ask a question about it. This is just what I thought of out of my general knowledge. Now my thought is that if I do this, I want to keep my roll centers pretty much the same, correct? Thats going to mean a good truss setup on the 14 bolt. I was thinking about the BTF one but that is far too low for my liking.
 
Roll center height with the panhard will be set by the height of the axle attachement point. Not familiar with the "BTF" set-up, what is it?
FWIW, the total roll axis in road cars is rarely level. Not sure that this is a dynamic worth pursuing off road. An ideal roll axis would pierce the CG.
 
The BTF bridge is what I used, and yeah, it's low. I originally got it planning to try to stay low under my tank, but of course that mussed up the numbers pretty bad, so I made changes to go taller, then had to deal with those "towers"... :crazy:

And while roll axis piercing the CoG might be great for road racers, I'm not sure if it would be completely good for us. Talking outside my knowledge here, but I've seen the point made that this would result in very little feedback before going over. It seems obvious that this would let you go further over without going completely over, but feedback is good.
 
I've never run a panard bar on a leaf sprung 4x4. But the '69 Mustang we ran as a pro rally car we used "Watts" linkage in the rear for the same reason. With watts linkage we had all the benefits of axle control without the side load that a panard bar can put on the axle.
 
84_Chevy_K10 said:
I don't know, I personally think that it's overdue that a Jeep Wrangler have a triangulated 4 link in the rear and end the madness with all these panhards and their inherent problems.

Wonder if it'd just wear bushings too fast to be acceptable or something? (I'm talking about the rear here)
Click to expand...

More expensive.

Harder to package in the vehicle.

Offers zero benefit to almost everybody who would buy a new Wrangler (even the few true off-road people who would want a triangulated 4 link would most likely want more lift, which means redoing everything anyway.............).

The typical panhard bar setup rarely has any issues in a stock application. It's only when you start modifying one of those vehicles, or start trying to add a panhard to a vehicle that never had one originally, where you have issues and that's mainly due to a lack of knowledge regarding the proper design.
 
6.2Blazer said:
mainly due to a lack of knowledge regarding the proper design.
Click to expand...

Thus why I started this thread :D

A Watts linkage is only good for street or dirt cars, I think it would bind in off road conditions, and be more complex than is neccessary. I've never seen one first hand, just seen them in chassis books.
 
here we go, another of my infamous multi-replies........

For some reason I never saw Marv's diagrams the first time I looked at this thread. I'm curious about the reasoning behind the extreme lateral shift of the RC. As I understand it the def of the RC with a panhard bar is that it will be at the height of the axle attachment point and centered laterally on the housing. I believe it stays centered on the housing and at the height of the housing pivot, but always projected in the direction of Gravity. So it's location in extreme articulation should be at the ture vertical height of the axle attachment point directly over the center of the housing. In other words vertically centered on the housing and horizontally at the height of the housing pivot. This will cause some lateral shift relative to the frame as the housing twists relative to the frame, but I don't think it can reach clear to either pivot point.

BadDog, I think you might be right. I was in a hurry and didn't think it thru. If the total RC pierces the CG then the boody will not lean over on a side hill until the CG is vertically outside the edge of the contact patch of the downhill tires. Once there it will flop on it's side, or worse.
Now consider what happens if the RC is above the CG. As the sidehill lean angle increases the body tends to try to stay horizontal. It becomes, in effect, a pendulum. I think that's good, but I don't know how much of a good thing it is.

A Watts linkage is a beautiful thing. Within it's narrow motion range. The bellcrank pivot actually travels in a modified 'S' curve. In most applications the motion range stays within the small vertical to nearly vertical travel section of the curve. Once you exceed that range, things rapidly go to $h1t. The WOB Link has a better curve (taller straight section) but even it won't quite do the job in this application.

In road racers the Roll Axis rarely is anywhere near the CG. The front RC is at, or near, and sometimes below pavement level. Camber curve is more important to them than RC height and you can't have both. At least not with any linkage currently known.
 
Like Russ said, moonbuggies have very tall RCs(I'd venture to say at or above CG) like you say, they stick pretty darn well to the sidehills. So much I need to learn yet. Some reason I just started to grasp this RC, RA stuff just before I made this post. I've read chassis books and it sunk in but I don't use it enough so it went away. Thats why I'm here at school, hopefully they get really technical with me in class. I've heard they don't get very technical but I'm gonna make that teacher sit down and teach me the real stuff I came ot learn.
 
I run a 91 Dually with a 454 and a SFA. My front axle moved around quite a bit on the steat with such a heavy truck and a big trailer. I fabbed a panhard bar for it and in rides so much better on road and doesn't hurt me off-road. I have no problems with about 10,000 miles on the swap.

Tyler
 
i think the necesaty of a panhard par depends on how high you've lifted the truck. the bigger the arc in the spring the more leverage the axel has on the spring to push it from side to side. i put a panhard bar in my truck with a d60 and leafs and 10"lift as well as a crossover and hydro assist and i love it. it drives really good and i haven't noticed any lack of poformance off road. got no bumpsteer and i tryed the flex with and without it hooked up and it didn't seem to limit the travel.
 
If your planning to do cross over steering with NO hydro assist, it's not a bad idea. Ive noticed with crossover steering that the forces tend to push the frame side to side wich twists the shackles side to side. I have replaced several poly bushings, even the Greasable Offroad design one's. Hydro assist helps by taking the strain out of the side to side forces and so will a panhrad bar
 
seems like I post this up about once a week lately.....
Old wally panhard pics

It will bind the suspension. Get out the drawing tools and draw a panhard bar about 40" long and let it drop from level 10" or so. For a 10" drop I get about 1.25" lateral motion. Your leaves aren't going to fully agree with this situation. It can work but it won't be bind free.
On roll centers: My front suspension worked very well, in fact, at the time the reason I went to coilovers wasn't for more flex but for more wrap control and less bind in the suspension. there were no quirks at all, at higher speeds or slower speeds.
 
So can anyone tell me why the panhard has to be the same length and the same angle has the draglink (to reduce bumpsteer)? Plus why cant you run the panhard from the frame on the pass. side to the axle on the drivers side if it does match the draglink? :confused:
 
Because the track bar controls the arc that the axle moves in, but the drag link controls the arc that the knuckle mounted drag link end moves in. If those arcs are different, the result is that the knuckle is turned, and the axle will "steer" back and forth as it moves up and down. Hence, "bump steer".

In other words, if the axle arc does not match the drag link arc, then the axle will shift sideways more than the drag link end (whose arc is controlled by the drag link) so the axle will steer as it moves up and down. Crossing in the opposite direction from the drag link would be the worst case scenario because the axle is shifting in the OPPOSITE direction to the drag link end mounted on the knuckle.

Those arcs will be different if the radius is different (i.e. different length of the bars), or if their starting angles are different. The rate of change (side to side) is also different when the starting angles are different, even if the lengths of the bars are the same. Consider an exaggerated example to show the effects more clearly. Imagine the 2 bars being the same length, but one starts level, the other starts angled 45* down. Now imagine (or draw) what happens when the axle moves down 2" or so. The end of the bar that started level has not moved left-right much at all with 2" downward movement. But the one that started at 45* will have moved almost as much to the side as it did down.
 
So you are saying there is no way to match the arc of the draglink and the panhard if they are different lengths even if they are running the same direction? How come the new Ford trucks come this way?
 
That is correct. The arc is controlled by the radius and that's all there is to it.

As for Ford, Dodge and other setups, it depends on the application and the person as to what levels of bump steer are acceptable. By changing various parameters you can minimize the deviation for finite ranges of movement, but the only way to keep bump-steer near "zero" over a relatively large range of motion is to have both drag link and track bar at the same angle AND same length. Change either of those and you're going to see increasing bump steer with additional travel one way or the other.

And in most cases where you have bump steer, the *rate of change* of that bump-steer is going to *increase* at greater than linear rates as you increase the amount of travel. So if you double the travel, you may get *4 times* as much bump steer. That means that for the relatively small amounts of travel a typical stock(ish) vehicle will see in normal use, you may not even notice it. Stock suspensions often won't travel that far anyway, even in hard use, due to various factors like suspension bind.

And this is the same physics that force the stock GM steering to cause trouble when you have angled (or "z" bent, the line between the pivots is the ONLY point of interest) drag links. Even when completely horizontal (which is how the suspension was designed by GM to work) you can definitely feel the bump steer even in a stock truck. But when the drag link is angled it's MUCH worse due to the arc being even MORE different from that traveled by the axle. And any decent off-road lift will allow enough articulation that you won't have ANY steering with the driver's front tire drooped. It's all about the differences in arcs/radii and their interactions.

So, most any vehicle has some amount of bump steer, including stock GM, Ford or Dodge trucks with or without factory track bars. But how much is too much can only be answered on an individual basis.
 
You must log in or register to reply here.

Latest Posts

Top Bottom