Watts link for first gen camaros

[clancj]

should'nt the bars reach from the frame on one side to the axle on the otherside? i dont see how the bars will pull/push when both bar ends are essentially on the axle?



i must be missing something? explain?

[The WidowMaker]

should'nt the bars reach from the frame on one side to the axle on the otherside? i dont see how the bars will pull/push when both bar ends are essentially on the axle?

on a panhard bar, yes. but this is a watts. on a chassis mounted watts, you have a crossmember that ties into the frame on both sides and allows the bellcrank to be mounted in the middle. that point is then stationary and takes the place of the frame rail mount. the two links then travel in either direction from there and mount to the axle. the bellcrank cancels out the lateral movement caused by the links arc.

[clancj]

on a panhard bar, yes. but this is a watts. on a chassis mounted watts, you have a crossmember that ties into the frame on both sides and allows the bellcrank to be mounted in the middle. that point is then stationary and takes the place of the frame rail mount. the two links then travel in either direction from there and mount to the axle. the bellcrank cancels out the lateral movement caused by the links arc.

thanks for watts info. So, i gather its purpose is to keep the axle stationary between the frame rails? (a good thing) If one side were tied to a frame rail, (like a panhard bar) would it function the same? would it also have anti-sway properties (more of a good thing)?

Sorry for all the questions, just try to get a handle on how all these suspension components work.

[Kenova]

I believe Steve Rupp posted a video of Penny's Watts link in action. The video does a good job of illustrating exactly how it all works.
I was surprised at how little the bell crank actually moves.

Ken

[Gitter Dun]

thanks for watts info. So, i gather its purpose is to keep the axle stationary between the frame rails? (a good thing) If one side were tied to a frame rail, (like a panhard bar) would it function the same? would it also have anti-sway properties (more of a good thing)?

Sorry for all the questions, just try to get a handle on how all these suspension components work.

No worries on all the questions, this is a great site with alot of knowledgable folk. Yes, the watts link's main purpose is to keep the differential stationary just like a panhard bar. The difference between the two is that the panhard bar is attatched to a fixed location on one side of the car and creates an arc when in motion on the other side of the car. The arc it creates allows for a little bit of side to side differential movement to where the watts link wont. In a correctly installed panhard bar the movement isn't much and I believe the key is to make the panhard rod as long as possible.

I am certainly no expert and would love for anybody else to chime in on this and correct me if I'm wrong.

On your other question, thats a good one. I'm not 100% sure that the chassis mounted bell crank style watts link wont help with a bit of anti-sway.

[MonzaRacer]

On a panhard bar you will have an induced arc, yes it needs to be as long as possible, preferably mounting should run from outside of one frame rail to at least the other frame rail in width. and angularity needs to be low so as to not cause binding points.
BUT you also have to remember the a panhard bar will upset Roll Center, thats the point that the cars left/right balancing point(think corndog stick through car lengthwise) is in the rear.
Quick and dirty the front roll center can be assumed as approximately the camshaft centerline, and this is also the design point we also draw through when figuring suspension too.
but as your car rolls over in turns the side to side shift, while minute may cause instability.
with a watts link there is no bind, no movement side to side and you can raise or lower it to help predict the RC height. Lower, and the car tends to "roll" over or lay over to the inside of the turn, and this tends to make weight transfer and load the inside tire harder. Higher and it will do less rolling thus not loading the tires with top weight but will load more sideways.
Basically the Watts will reduce or eliminate SOME cars need for a stabilizer bar. and it changes shock valving needs.
All in all after many years of NOT understanding the design as I should I finally got it to soak in. My terminology may be off but after seeing suspension video(dont ask i cant remember where I saw it one of those great sites you can never find again) on a suspension sight it explained a lot and let me et a handle on it,,, now I want a watts link in my Monza,,, and maybe my Caprice if I redesign the rear suspension.
Mainly casue a triangulated 4 link doesnt work well with a watts.

[Bryce]

On a panhard bar you will have an induced arc, yes it needs to be as long as possible, preferably mounting should run from outside of one frame rail to at least the other frame rail in width. and angularity needs to be low so as to not cause binding points.
BUT you also have to remember the a panhard bar will upset Roll Center, thats the point that the cars left/right balancing point(think corndog stick through car lengthwise) is in the rear.
Quick and dirty the front roll center can be assumed as approximately the camshaft centerline, and this is also the design point we also draw through when figuring suspension too.
but as your car rolls over in turns the side to side shift, while minute may cause instability.
with a watts link there is no bind, no movement side to side and you can raise or lower it to help predict the RC height. Lower, and the car tends to "roll" over or lay over to the inside of the turn, and this tends to make weight transfer and load the inside tire harder. Higher and it will do less rolling thus not loading the tires with top weight but will load more sideways.
Basically the Watts will reduce or eliminate SOME cars need for a stabilizer bar. and it changes shock valving needs.All in all after many years of NOT understanding the design as I should I finally got it to soak in. My terminology may be off but after seeing suspension video(dont ask i cant remember where I saw it one of those great sites you can never find again) on a suspension sight it explained a lot and let me et a handle on it,,, now I want a watts link in my Monza,,, and maybe my Caprice if I redesign the rear suspension.
Mainly casue a triangulated 4 link doesnt work well with a watts.

the roll center in dependent on suspension geometry. The Cam centerline is the approximate center of gravity.

The pivot point on a watts link defines the roll center as long as the other suspension link are parralel.

If you transfer more weight you load the outside tire harder.

Im not sure why the wattsl ink would change the need for a sway bar? Roll stiffness is dependent on CG, roll center and spring rates. The panhard and watts could both have the same roll center. therefore the same need for a sway bar.

Why does a tri-4 link not work well with a watts link? If a watts is no bind in vetrical travel then it would work fine with a tri-4

[The WidowMaker]

thanks for watts info. So, i gather its purpose is to keep the axle stationary between the frame rails? (a good thing) If one side were tied to a frame rail, (like a panhard bar) would it function the same? would it also have anti-sway properties (more of a good thing)?

Sorry for all the questions, just try to get a handle on how all these suspension components work.

i dont think anybody will ever have problems with questions, and im still learning myself :. its purpose is the same as a PHB, a lateral location device. a watts that is tied to the both frame rails and the center of the axle is known as an axle mounted watts. neither has any anti sway properties. there are pros and cons of both, but both will allow the axle to migrate slightly. it gets more extreme as the roll center is moved away from the axle centerline height. i did some math in the other forum (link at beginning) but those guys dont like math. i need to do some accurate drawings to show my findings.

[Gitter Dun]

Thanks Lee. I have a question. When I installed the watts link I made sure the rods coming off the bell crank to the axles were level at ride height. If I am to adjust the bell crank up or down they will no longer be level. Can you tell me how this may affect the car?

[Bryce]

Thanks Lee. I have a question. When I installed the watts link I made sure the rods coming off the bell crank to the axles were level at ride height. If I am to adjust the bell crank up or down they will no longer be level. Can you tell me how this may affect the car?

That will have no affect as long as the bell crank does not bind at full suspension travel. The rule for Watts link is the links need to be parralel at somepoint in the travel.

[Gitter Dun]

Thanks Bryce. Now from what I understand, the leaf spring and watts link each define roll center. If thats the case do i want to match roll centers by adjusting bell crank. I have a feeling I want to lower my bell crank so that the center of bell crank is parrallel with leaf spring perch.

[Bryce]

I am not up on my leaf spring geometry but I think on parralel leafs its the front spring eye height that defines roll center. On leafs that converge as they go forward the RC is the height of the convergence point. If you add a watts its now a roll axis.

Im sure someone else could better answer this.

[MrQuick]

partially, but correct.

you have to watch the watts height cause often times an added watts will actually raise the roll center height or not even change it.

Gaetano's just going for tire track locking and adjustability. He's also 2 steps closer to getting his 3 link made.

[The WidowMaker]

That will have no affect as long as the bell crank does not bind at full suspension travel. The rule for Watts link is the links need to be parralel at somepoint in the travel.

correct. people forget that the car is at ride height very little while driving. something is always happening and something is always moving. if it needed to be parallel at ride height it would never be there for long.

Why does a tri-4 link not work well with a watts link? If a watts is no bind in vetrical travel then it would work fine with a tri-4

with a c4l and a watts you have two roll centers. in addition, the bushings must have compliance or a c4l will bind. the watts complicates the movement of the c4l and can induce even more bind. running rubber bushings usually solves this issue.

[MrQuick]

Tim, would you know at what point of travel a converged 4 link would bind?

vince

[Bryce]

A C4L is always in bind; it's an over constrained system, that is why it needs a compliant bushing. What I was saying is a watts would not add more bind to an already bound system.

With compliant bushings or heim joints the suspension can articulate around 6 degrees. That is plenty for these cars.

[AMC Racer]

Why is a C4L over-constrained? There are 6 degrees of freedom with a solid axle rear axle suspension so you need 4-links to constrain the axle movement to get just 2 degrees of freedom of jounce (up & down) and roll. More than four links is over-constrained. A link by definition is free to rotate about it's pivot point and can only take loads along its axis. Limiting freedom of movement at the link pivots constrains the system so causes bind and bending in the link, e.g. fitting rigid bushings or bushings with limited compliance. Proper selection of bushing material is needed to minimize constraint in the system or use sphericals (heims).

A C4L has 4 links so is not over constrained. A parallel 3-link with watts or panhard has 4 links so is not over constrained. A parallel 4-link with watts or panhard has 5 links so is over constrained. Adding a watts or panhard to a C4L adds a 5th link so over constrains the system. I've done layouts of various link suspensions and all will bind in roll if the links aren't free to rotate at the pivots. In most cases the amount of movement at the pivot is small, so the bushings don't need much compliance. Some link suspensions using particularly short links (i.e. Mustang) need significant link movement to accommodate roll so tend to bind - particularly if fitted with relatively rigid bushings.

A properly designed C4L will accommodate much more than 6 deg. roll and should keep the axle centred in jounce without the need for secondary lateral control.

[parsonsj]

A C4L suspension is over-constrained because the links aren't parallel. Bryce already said it, but I'll say it again: without compliant bushings, brackets and control arms, the C4L would allow zero roll.

jp

[AMC Racer]

Do the links in a parallel link system stay parallel in roll? Must be missing something as the layouts I've done show all systems need freedom of movement at the link pivots or you get zero roll, i.e. it's not an inherent issue just with the C4L?

[parsonsj]

Do the links in a parallel link system stay parallel in roll?

Of course. The brackets move with the rear end housing, so the links remain parallel: both top to bottom and left side to right side. A parallel link 4 link (more commonly called a 4 bar) is only limited by the joint articulation. Compare that to a C4L: the links aren't parallel in either plan, side, or front/rear view. As a C4L suspension rolls, the linkage arms need lengthen/shorten to allow for roll. As others have noted, a small amount of compliance will allow enough roll for passenger car usage.

jp