Basic measurements for them fancy 4 links

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slidewayswrx
Would the axle shift be the basic reason for the Watts link then? Never really dug thoroughly into that idea?

Yeah.. a watts link would cure that, as well as a triangulated 4 link (without a panhard bar).

Nothing like getting used to driving a twin 5 link (4 link with panhard) vehicle.. When I first got my little Jeep it could do 1/2 a lane change on its own when crossing bridge expansion joints. Eventually you get used to it and compensated, but the first few times its fun.

The longer the panhard and closer to level it is at ride height should lessen the effects though.

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This isn't floor mat anarchy

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alosix
Nothing like getting used to driving a twin 5 link (4 link with panhard) vehicle..

Yeah driving a car that's incredibly stable over bumps on a gravel road does take some getting used to.

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sidewaez

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alosix
Nothing like getting used to driving a twin 5 link (4 link with panhard) vehicle..

Yeah driving a car that's incredibly stable over bumps on a gravel road does take some getting used to.

Not trying to say it can't be properly sorted or that it isn't on most cars. The stock Jeep TJ configuration was good for some surprises under the right circumstances. Heck.. the rear suspension would torque bind and with a little practice you could carry the driver's side front tire for quite a distance in a completely stock vehicle.

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This isn't floor mat anarchy

Keep in mind that the Watts linkage presents some challenges for rally. One side of the linkage sits low, and you have to have a long, very strong vertical anchor point sticking down low on one side of the car for that lower link. Can be pretty exposed to damage for rally. Panhards are much simpler. My old Opel rally cars never acted up with them with fairly long travel, so I'll stick with that design.

no plans here to go to a watts, Charles has gone that way and I was just trying to see the advantages.

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Zap zap my ass...

Actually I have no beef with the watts link, and the geomatry works out better when you really start talking about axles movin up and down, ie the axle not shifting from side to side because of the pan hard bar getting shorter.

At least in the case of the rx7 the watts link is placed fairly high on the axle, making the lower link about parallel with the axle center line. It actually sits on the front of the axle so the upper link has to go over the 3rd member. All in all it keeps it out of the dirt quite well.

I was talking to Hurst at mt hood last year about his old rx7 and he said the watts works well for him, and once he ditched the upper bars in favor of a single 3rd link the whole rear axle worked a millions times better.

As for charles watts link, yeah I think a simple pan hard bar would have worked the best for that, but twas not my money or car so to each there own.

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"Rally racing makes a heroin addiction look like a vague craving for something salty"

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slidewayswrx
no plans here to go to a watts, Charles has gone that way and I was just trying to see the advantages.

Well there you have it: no advantages, so of course that's the thing to do.

This is one of those things which crop up constantly.

Fred has some shit standard set-up. Researches and sees that Watts is theoretically a better set up...
And the truth is............. it is....but is: extra cost, extra fab, extra maintenance, potentially more shit to go wrong and be worse when it isn't tip top enough an advantage over a much simpler to fab and do panhard rod which is already a big improvement over the crap he had?

Its the "a good plan today is better than a perfect plan tomorrow" deal.
A good panhard rod has let 10s of thousands of guys drive their cars faster and harder than any of us ever will.
Good enuf.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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alosix

Not trying to say it can't be properly sorted or that it isn't on most cars. The stock Jeep TJ configuration was good for some surprises under the right circumstances. Heck.. the rear suspension would torque bind and with a little practice you could carry the driver's side front tire for quite a distance in a completely stock vehicle.

I think that has more to do with a Jeep being a torquey short wheel base vehicle than the 5 link setup. Leaf sprung CJ's used to to this too. You could do a 'Michigan Left' in one of those things and not drop the left front wheel down until you let off the throttle or had to shift.

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Morison
[jvl] Ohh noooohs! There's an h'off tawpik thread in the gent-urinal dick-cushion four-hum. THINK OF THE CHILDREN!!![/jvl]

Edited 1 time(s). Last edit at 03/09/2012 10:29PM by RallyTaco.

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john vanlandingham

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slidewayswrx
no plans here to go to a watts, Charles has gone that way and I was just trying to see the advantages.

Well there you have it: no advantages, so of course that's the thing to do.

This is one of those things which crop up constantly.

Fred has some shit standard set-up. Researches and sees that Watts is theoretically a better set up...
And the truth is............. it is....but is: extra cost, extra fab, extra maintenance, potentially more shit to go wrong and be worse when it isn't tip top enough an advantage over a much simpler to fab and do panhard rod which is already a big improvement over the crap he had?

Its the "a good plan today is better than a perfect plan tomorrow" deal.
A good panhard rod has let 10s of thousands of guys drive their cars faster and harder than any of us ever will.
Good enuf.

For sure if starting from scratch the need to build a watts links isnt there, you can have a pan hard bar and it's done and done.

But that's kind of the path his car took, the "simple" volvo build ended up being, well, not very simple any more.

It should be interesting, WHEN it gets to some level of completion.

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"Rally racing makes a heroin addiction look like a vague craving for something salty"

i have a major beef with the Watts, since when you combine it with upper link(s) that actually allow the rear suspension to move, the back end does a bunch of unsettling things over one-wheel bumps, since the roll center is so far away from the lower links' plane.

It's not easy for me to describe it, but it's like the toe changes a bunch because the high Watts is making the axle swing to the side over one wheel bumps. A Panhard more inline with the lower links eliminates this.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Thanks, Pete, and good info for all; I wondered when someone would figure to mention this. A Watts linkage moved up vertically to reduce damage from the road is typically attached to the top of the pumpkin. If I remember right (and feel free to check; it's been a while), that moves the rear roll center up along with the attach point. On the 50 series Opels (first Manta and first Ascona models), the axle end of the panhard rod connects into the axle at almost the exact height of the 2 links, all of which which are below the axle's center line. Keeps the rear roll center lower....Putting a Watts linkage center attach point that low is just about impossible.

The way I'm picturing the suspension moving, on a one wheel bump with a Watts, the axle rotates around the center pivot, and if that center pivot is pretty high up, the axle swings to the side.

With a Panhard, on a one wheel bump, the axle rotates around the chassis end, or the axle end, depending on which side it is. It doesn't make the rearend doe-see-doe.

It's not *just* the roll center height, it's the pivot height in relation to the trailing links, and how those angles are all interrelated. The RCH isn't strictly the location of the Watts/Panhard, it's where the axle intersects a line going from the centerline of *that* device to the centerline of where the trailing links are pointing, and if that line is angled, then the axle is going to want to *move* along that angle.

Sure, the Escorts used a Watts... they also put it dead center of where the four parallel/even length links were. Well engineered setup, in other words.

I'm not an engineer, I just put stuff together and see what it does, and then learn why it works well or works awful.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 03/10/2012 02:27PM by Pete.

Just to throw it out there, I know of at least one application of a watts having the pivoting section horizontal instead of vertical, on the bottom of the diff. Needs Heim joints and probably not too applicable for rally, but it's at least possible.

The outfit that designed this (2 brothers out of SoCal) for early Mustangs...







Not much good for Rally, but could be killer on tarmac ...

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SteveL
This is the point in the killing spree when you really should turn the gun on yourself