panhard vs wattlink vs wishbone?
 

Hey all!

First,have to apologize my english.

I'm new in here on this forum.

I'm not new in fabricating cars and chassis.

Here I've been watching car porn at project update almost year now and now I have to ask this:

Without putting anyone or they skills down :thumbsup:

I am blown away with stuff seen in here.:willy:

Why do guy's built they rear ends with panhard and wattlinks

when there is much easyer and stronger way to do it with wishbone like in a drag chassis?

I know that panhard is not possible to make accurate if you have lot vertical axle travel like in 4-link.

It'll allow sideway axle movement and you have to make horrible brakets to your frame and axle.

When the wattlink is accurate but involves more fab than wishbone. And you have again those bracket...

I've know Wattlink from group II rallycars in Europe into '70 and '80.

It is excellent system but it is so much fabrication and it is not pretty (Read: simple design)

You can built wishbone anywhere around your rearend. Only that it's have to be along your chassis, not sideways like panhard.

And when you get it right, it stay's right regardless how much suspension travel you have.

I use to run with panhard on my blown pro street/touring Swinger, used 4 link,panhard and 30x13.5" Mickey rad Et's.

Had many problems with panhard, then I chance it to wishbone, had none sence and have to say that I really did drive it,

a lot, I did make trips to foreign countrys and so on.

I will take a stab at this.

I think the wishbone would limit suspension articulation, it would bind in body roll. At what degree of body roll does it bind? I dont know off the top of my head. So that would be the main reason. It would be like ladder bar for the street, it can work but not ideal.

Second, I think watts look amazing. Here is my solution to a watts link, I have not seen this design yet.

http://media.motortopia.com/files/ca...Thumbnail1.jpg

http://media.motortopia.com/files/ca...Thumbnail1.jpg

Actually, if constructed correctly, the wishbone is about as bind free as you can get.

There are 2 definitions of a wishbone...

The off-road guys refer to triangulated upper links with a single pivot on the axle housing (basically a trinagulated 4 link design). No real problems with that, except you have a relatively high, non-adjustable roll center (the axle pivot).

Drag racers refer to a Y shaped assembly that mounts between the lower links of a straight 4 link suspension. This design won't allow quite as much roll, and offers a very low, non-adjustable roll center. Either type should perform well enough, as long as the link angles are at least 60deg to each other.

You don't really need the adjustment holes out at the ends of the axle housing. Those points can be at any height (within reason), as long as the relative height difference is the same as the center to center distance on the bellcrank. Adjustment out there only puts the Watts in a different point in it's natural travel.

We've built a number of those "reversed" Watts links. The only issue with them is the roll center height moves with suspension travel (fixed roll moment). If the bellcrank is fixed to the axle housing, then the roll center is fixed in relation to the ground (roll moment changes with travel).

Ray I agree about the adjustments on the axle end. Those are not needed. The bars only need to be horizontal at one point during the suspension travel. Those were there as an adjsutment tool to dial everthing in. I may go another route.

As for roll center migration. I want to keep the roll center at a fixed length compared to the the CG height. Therefore you would have the same swaybar at all suspension heights/ roll center heights. You would end up with a stiffer sway bar as the CG of the car lowers, during a bump and vis-a-versa. Also think about the front suspension you have a roll center that typically changes height with ride height changes. So why not match that with the rear suspension.

Guess I shouldn't have said "issue", more like "difference". :D

That design definitely lends itself to use with an anti-roll bar.

What about if you triangulated the the lower control arms? What would that do with the fixed watts link? Would that even work? Would it work better? I am trying to figure out how I could make something like this work on my impala. It has a single upper link RT side, and two triangulated lower likes. All are adjustable as it was a "sleepy" street car. I had a diagonal bar on it, but now that I am changing games, I need a different device. I really like the watts look over the panhard bar. It may win out in the end though. Any ideas?

Richie

Yep, that was the plan another tuning device.

The lowers aren't really "triangulated" in the sense that they are the lateral locating device. You only need (and can use) 1 lateral locating device. The triangulated lowers with straight uppers are called a "Satchell" link setup.
http://i30.photobucket.com/albums/c3...tchellLink.jpg
I would avoid that type of system in a high-horsepwer, big tire car for one reason. Under acceleration, the thrust force from the rear tires is ALL running through the lower links. In that case, it is a good idea to have them parallel to the chassis centerline, and tied directly into the frame.

A Watts link, panhard, etc. should really only be used if all the links run straight.

Lateral-dynaimcs 3 link uses triangulated lower links with a center upper link and a watts. With triangulated lower links part of the roll center is defined by the intersection point.

A Watts link, panhard, etc. should really only be used if all the links run straight.[/QUOTE]

thanks for the input. i wanted to keep the factory three link without having to do anymore frame mods. except maybe put the panhard or watts back on.

i guess that is the type set up i am trying to do. just playing around with some ideas now. thanks for the input.

The lower links on the Lateral Dynamics setup aren't really "triangulated" either. The angle in the lower links comes from the forward pivots being relocated slightly inboard for tire clearance.
http://i42.tinypic.com/mcx6dj.jpg
For all intents and purposes, we could consider those "straight" links.

Just posting this to try and help any confusion with the Satchell design.

Thanks again. I guess triangulated is too far fetched of a description. They are merely angled. I don't mind stealing knowledge though.....so keep on educating me.

Link suspension 101...?
 

I just grabbed this picture off the net, but it illustrates the main concern with a true triangulated link suspension.
http://www.akfabshop.com/alaskaoffro...k_Topangle.jpg

In this case, the upper links are the lateral locating device. There is no Panhard bar or Watts, etc. It is the angle between the links that holds the rear axle in place. The wider the angle (red lines), the better the job the links do of controlling side motion. That's why most factory setups are close to 90deg included angle. BUT, this leads to short upper link length, lots of pinion angle change, and a lot of bushing bind in roll. Narrowing up the angle (green lines) frees up the suspension in roll, but does a poor job of keeping the housing firmly in place under side load. In a "lateral-g" car this is far more important than free movement, as travel and roll angles are purposely limited (low ride height and flat cornering). 60deg is the typical minimum included angle for a street vehicle, closer to 90deg would be better.

The intersection of the links does define the roll center in height and location relative to the axle housing. That is one reason I personally am not a big fan of the "reversed" triangulated links (narrow at the front).

Now, back to the lower links... As I mentioned earlier, ideally we would like to keep the lower links as straight (to chassis centerline) and level to the ground as possible. The bigger the tires and engine (torque output), the more important this becomes, regardless of what we are doing with the upper links. The more the lower links are triangulated, the more the "push" from the rear tires/axle is going to try to move the housing around. It may not actually move, but the loads on the link pivots, Panhard bar, etc. go way up; especially when we have a difference in rear tire loading (like accelerating out of a corner:wow:?). Combine that with the roll center being low and located way ahead of the axle centerline, and you have the potential for a lot of "monkey motion" from the rear tires during hard use.

Now for my disclaimer...people do all of these "bad" things with suspensions all the time, and enjoy the hell out their cars that way. I believe that designing these problems out from the start gives the driver a better seat of the pants feel and makes the car more consistent, easier to tune, etc. Bottom line is, build it safe, drive it, and have fun...:thumbsup:

that's deep. and i thought explaining photosynthesis and respiration to my freshmen was a job!:bow:

The lower links on the LD setup are angled inboard (plan view) for a very specific reason, and it's not tire clearance. In doing so, they form a lateral resistance that in conjunction with the bellcrank position (which in this case defines the rear roll center height), defines the rear roll axis. Trust me, I know the guy who researched and designed this setup (he's kind of a difficult person to deal with). With the angle of the lowers in plan view, and more importantly the fact that there is only one upper link (relative to Terry Satchell's design illustrated), one additional constraint is needed to appropriately locate the rear laterally (Watts, in this example). Actually, even WITH the modest lower angle, the lowers would be sufficient enough to locate the rear laterally IN THE CASE of a Satchell. However, it would be very impractical in that the entire system would need to be made so strong as to eliminate any bending and flexing, or the system wouldn't work, which is why the typical angles on those types of setups approach or exceed 45 degrees (nature likes that number...).

The LD setup was designed to have a bit of liberty to adjust the rear roll center height to accomodate roll resistance and jacking force reduction, as a primary adjustment. One could also use the system to define the rear roll axis as a primary setup and let other parameters "float," but typically this is not the case. The entire adjustment envelope of that system is such that even at the extremes, nothing gets too far out as to create a diabolically handling car, at least at the rear.

That is certainly one design approach, but there is more than one way to skin a really fast cat. The LD approach considered this, and designed differently for very sound engineering reasons. In terms of force application being an issue with angled lower links, again, if the structure, links, rear housing and all other mechanicals are sufficiently rigid, this is not an issue. Certainly within the traction potential of a 345 wide R Racing compound road race tire in this example, a "modest" contemporary "Pro Touring" inspired engine (750 HP?), and portly curb weight (3400-3600 lbs, more?), there is not an issue with this approach. Honest. And I'm not trying to get into a wee-wee contest at all, there was a LOT of thought put into that system and virtually no design element was done without regard for consequence. You need to pick your battles, as you can't have it all in one package.

Back to your regularly scheduled program.

Mark

Apologies for my lack of insight as to the LD design paramters. I have seen a number of these setups done in exactly that fashion for tire clearance. My comments regarding keeping the links straight and level are general "can't go wrong" guidelines for those who are unfamiliar with the intricate details of link type suspensions.

About wishbone, I think some explaing is in order.

I'm thinking of dragstyle,not offroad full welded structure, here we have a simple capitol A with one extra tube coming straight down from to top of the letter and there is another free movement tube going out inside this tube and they make a kind of telescope structure. There is two connections at bottom ends of letter A and one on the end of inner tube. It will go shorter or/and longer with suspension movement. So it will never ever prevent it and nothing like ladders cos Wb not full weldet structure.

Exwestracer is right track with me here. Wb is problem free desing. It's more free than wattlink.

I calculatet that it can be fab it around rearaxle 8 diffrent position and ways and all they can be same as cars centerline (or what its call'd)

If you use Wb it will take all side to side forces of your suspension link tubes.

Again, I not saying that you all are wrong, just that there is easyer way to do it right.:thumbsup:

This was the way I did it in my Swinger six years ago. I did welded some extra 1/4" plates after I bend it speeding way to fast in Estonias back roads.