Watts Link, No joke..... Options

[Sam Strano]

Sam,

I can see how the center pivot is adjustable up and down, which allows for roll center height adjustment. Is there also an allowance for vertical adjustment of the axle side of the horizontal links? I believe that optimum benefit of the Watt's linkage occurs when both horizontal bars are parallel to each other and to the axle and the vertical bar is perpendicular to these links when the car is sitting at ride height. If not, I think the non-optimal geometry has the potential to introduces scrub in either one or both turning directions.

Second, Do the rear brake lines which run along the axle need to be rerouted to clear the Watt's linkage axle mounts?

That adjustment depends solely on where you position the clamps and you can rotate them wherever you think you need them to be. Howvever if you check out some of the vids and things on Youtube, you can see them in action. Here's the thing, because there are two rods and they are equal length, they work opposite of each other. When one shortens, the other lengthens, in effect. This one video shows how it works in action (no drawing, real pictures): http://youtube.com/watch?v=-J4xkHuP7QY

[sgarnett]

The links should be set up to be equal in length. They should also, ideally be set up such that at ride height, the links are parallel and horizontal. However, as the suspension moves up and down from there, the Watts link still works as long as plenty of travel has been designed in.

So in practice, the main thing is to get the links horizontal, parallel, and equal in length at some point in the suspension travel, with the axle level. Moving the pivot up or down from there should still be OK. Now, you should be reasonable about it - don't set up the links with the suspension at full droop, but ....

The so-called "propeller" (aka bellcrank) should probably be vertical somewhere in the ballpark of halfway through the suspension travel just so you maintain plenty of travel. [probably wrong, see below]

It is important that the arms be horizontal when they are parallel (with the axle level), or there will be some unintended lateral movement as the suspension moves vertically.

In practice just set it up with the suspension loaded, the chassis and axle level, the links level and equal in length, and then verify that there is plenty of travel (ie that the in full droop the bellcrank doesn't reach horizontal).

This post has been edited by sgarnett: Jul 24 2008, 10:40 AM

[Major_Lee_Slow]

The you tube video isn't working.

All Watt's linkages do introduce scrub at their extreme travel point. However, depending on the length and ratio of the arms vs. the suspension travel of the axle, it may or may not be possible to get into that part of the curve with this system.

Just to make sure I completely understand the proper way to set up this system.
1. It appears that the axle mounts should be set so that they are parallel to ground to minimize the potential for binding during axle travel. (assuming the ground is flat and level) and that they should be mounted equal distance from the center line of the axle. This assumes that the watts linkage pivot is at the center line of the car and one wants the axle centered about the center line of the vehicle.
2. The two horizontal arms must be adjusted so that they are equal length. This is extremely important! If they are not equal length, then the benefit of the Watt's linkage may not be fully realized.
3. The vertical bar will not necessary be at 90 degrees to the horizontal bar at ride height (This will depend on the ride height of the vehicle and the roll center height setting)
4. Slide the center pivot up or down to to adjust the roll center and don't worry if the vertical bar is not at 90 degrees (as long as the horizontal bars are equal length and the axle mounts are properly located).

It would appear to me that a good starting point for the roll center would be at the middle of the axle because at this setting the linkages should be in there proper ride height alignment (parallel and 90) if everything is adjusted correctly (equal length parallel arms, the center pivot is centered on the vertical bar and the axle mounts are equal distant from the center pivot and the axle center). Since there really is not adjustment to the height of the axle mounts, it appears that the "ideal" alignment will only occur at this position. (Ideal meaning that both horizontal bars are perfectly parallel and the vertical bar is at exactly 90°)

My only concern,and this may be unfounded, is that the further the bars are away from "ideal" ride height alignment the system moves closer to the "scrubbing" part of the watt's linage curve.

[Sam Strano]

The video just worked for me. Try again. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) http://youtube.com/watch?v=-J4xkHuP7QY

[sgarnett]

Just to make sure I completely understand the proper way to set up this system.
1. It appears that the axle mounts should be set so that they are parallel to ground to minimize the potential for binding during axle travel. (assuming the ground is flat and level) and that they should be mounted equal distance from the center line of the axle. This assumes that the watts linkage pivot is at the center line of the car and one wants the axle centered about the center line of the vehicle.

No, the axle mounts should not be parallel to the ground. The links should be parallel to the ground when they are parallel with each other.

The video works fine for me, but it shows a setup with the pivot mounted on the axle instead of the chassis.With that setup, the roll center stays at a constant height relative to the ground instead of relative to the chassis CG.

This post has been edited by sgarnett: Jul 23 2008, 06:06 PM

[Major_Lee_Slow]

What I mean is that the "arms" of the axle mounts should be parallel to the ground. So they should stick straight back from the axle just like they do in the picture..

When I try watching the video I get a "We're sorry, this video is no longer available" It may be the firewall here at work, I'll have to try it when I get home.

[sgarnett]

What I mean is that the "arms" of the axle mounts should be parallel to the ground. So they should stick straight back from the axle just like they do in the picture.

Nope, look closer at the picture (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif) The arms should not be level. The aluminum links should be level, and to accomplish that the driver's side mount will be angled upward and the passenger side will be angled downward (or vice-versa, except that would probably interfere with the exhaust).

This post has been edited by sgarnett: Jul 23 2008, 07:23 PM

[Major_Lee_Slow]

Ok, I see it now, they are angled up and down (Man my eyes are starting to get old). They must be angled up and down an equal amount so that the arms are angled equally from the center pivot along the center line of the car in order to maintain an equal distance from the pivot.

Ok, here's another question. So the arms are attached to the axle tubes, what keeps them from slipping along horizontal length of the tube? Just the normal force and friction of the axle clamps? Should that area of the axle be "prepped" before installation (i.e. all rust removed).

One would think that this might be better than the current design because the current design only loads the axle in one spot and this design loads the axle in two spots, thus better distributing the load. Right?

[Sam Strano]

Friction/clamping is what holds the watts in place on the axle. However, as someone mentioned there is no reason that someone couldn't tack weld just to be safe if they wanted.

In looking at the design of some others for S197 Mustangs (also a PHB/PHB brace car and in fact of the same weight and a PHB only about 1" longer than a F-body) I think the Fays2 design is better. Check out what they are selling for $999 in comparison: http://steeda.com/products/steeda_watts_link_s197.php How about Saleen's Watts? http://www.haneymotorsport.com/HMSstang/HM...smustanglrg.JPG Also for about $1k and uses the diff cover as the axle mount. I don't know about you, but I trust clamping on the axle tubes a lot more.

I suggest that a good search for Watts Link would start. But more specifically look for '05+ Mustang stuff, as they are very similar in rear suspension and weight. Hell even the rear springs are on the axle now (stock rate of about 130 btw). (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) Sorry to say they have a leg up here on us due to numbers. There are a lot more Ford junkies than F-body ones, so despite the PHB arrangement being in place for 20 years from 1982-2002, it's just now that we are getting some of this stuff. I've been trying, but sometimes life intervenes. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

[sgarnett]

They must be angled up and down an equal amount so that the arms are angled equally from the center pivot along the center line of the car in order to maintain an equal distance from the pivot.

Well, it probably does make sense to do the initial setup with the pivot on the centerline of the axle at ride height. After all the lengths and angles are correct, and the axle is centered properly, then you can move the pivot (roll center) height to the desired position. As you said, the angles should be equal too.

Then lower the axle to full droop, and if the bellcrank is nearly horizontal, lengthen both links by the same amount and recheck.

While the axle centering can be fine-tuned by adjusting the links, that will lead to one being longer than the other. For that reason, I would preset the links to the same length, and position the arm/clamps to get the axle as close to center as possible before changing the links. If done right the first time, there should be no reason to ever move the clamps.

Of course, the setup tricks will also get some fine tuning after we start getting a few installed (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

This post has been edited by sgarnett: Jul 23 2008, 11:57 PM

[sgarnett]

The so-called "propeller" (aka bellcrank) should probably be vertical somewhere in the ballpark of halfway through the suspension travel just so you maintain plenty of travel.

Oops, that's wrong.

The links will be at their "shortest" or most overlapping position when the pivot is at the axle centerline.

This post has been edited by sgarnett: Jul 24 2008, 12:15 PM

[sgarnett]

Second, Do the rear brake lines which run along the axle need to be rerouted to clear the Watt's linkage axle mounts?

Is there any difference between 3-channel and 4-channel cars in the hard line routing on the axles tubes? I know there will be an extra rubber line from the chassis to the axle on the 4 channel cars, but is that only different at the center?

At least on my 2001 4-channel car, I'm pretty sure the brake lines will need to be rerouted a little to make room for the bracket clamp. Hopefully they only need to be raised an 1/8" or so to make room for the clamp underneath. They may need to go a little higher temporarily to get the bracket inserted between the line and the axle.

Is it possible to get enough clearance by just loosening and/or modifying the brake line brackets, or will the hard lines have to be bent a little? If so, what's the best way to accomplish it?

[nape]

Is it possible to get enough clearance by just loosening and/or modifying the brake line brackets, or will the hard lines have to be bent a little? If so, what's the best way to accomplish it?

I usually bend them by hand. As long as you aren't a caveman you can feel when the tubing has had enough and is about to kink.

Mild steel is pretty forgiving. I buy lines when I need to and I've made 3rd gen lines fit a 4th gen rearend even though the 4th gen is 3"+ wider.

This post has been edited by nape: Jul 30 2008, 02:16 AM

[Sam Strano]

The brake lines are easily pushed around. It won't be any trouble to get the clamps on the axle under the lines.

[trackbird]

Yes, there are some posts missing. Yes, I moved them out of this thread. If anyone has any questions, please feel free to send ME a message.

Warning:

Brian, DO NOT keep messing around with upside down questions and such in a sponsor thread.

Thank you.

TB

Sorry about that Sam. Back to your regularly scheduled discussion.

[Sam Strano]

Appreciate it.

[ESPCamaro]

and I think I am 3rd or 4th....plus I don't care WHAT color it is as long as I can make it go fast.

(IMG:http://www.frrax.com/rrforum/style_emoticons/default/2thumbs.gif)

[sgarnett]

Well, my mid-August test-n-tune has been cut from two days to one, and I'll miss the next event after that since my wife is having surgery. Maybe I should ship Fay a case of Full Throttle or Red Bull to help him pull the delivery date in a little (IMG:http://www.frrax.com/rrforum/style_emoticons/default/biggrin.gif)

[Sam Strano]

Just spoke to Fay2 regarding an update. Things are progressing and the estimated time to ship is now around 2 weeks. No actually date at this time. Parts are being cuts, jigs are made. When I get a more specific time and we get to around 1 week before I will begin to process the pre-orders. It takes time for the money to get transferred and Fays2 will want paid, so in order to get them out ASAP we will process orders when the build begins.

And here's the better news: Black is a go and will happen!

[sgarnett]

Will black be available at the same time as red, or will it be a later batch (and if so, how much later)? With availability slipping by a week or so (not that it's much of a slip, I'm not complaining), it sounds like I'm probably going to miss my window of opportunity for testing. If so, I may be back to caring [a little] about the color.

"POR-15 Patch" (the thick goop in a squeeze tube, available in any color as long as it's black) works great for permanently touching up powder coat scrapes and has become my new favorite color (IMG:http://www.frrax.com/rrforum/style_emoticons/default/biggrin.gif)

This post has been edited by sgarnett: Aug 2 2008, 10:29 AM