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Watts Design Question

AltBantam

Active Member
There is a lot of information on Watts Links online, even here. Some good. Some not so. I hope someone here can tell me if I am right or missing understanding.

I was planning on using a panhard bar to center my 4 link rear suspension. But it turns out I cannot put the bar where I wanted to place it and the tubing be longer than 33" from mount to mount. That comes up to .095" of side travel if the suspension travels the full 2.5" up or down. Looking around, I realized I have nearly enough material to building my own watts link. So here is my question. I have seen manufactures, (Ford, Dodge, etc) have the bar mounts above the bell crank, angled downwards. I have read many say keep the bars parallel to the rear axle/ground. It seems as long as the distance between the mounting points (A) for the tubes and the bell crank (B) is the same, it should not matter how high the mounts are mounted off the frame (See image below). Am I right or am I missing something? Thanks
 

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Keeping the links close to horizontal greatly increases the resistance from "side loading" on the tubing. If you look at the drawing, consider the low resistance from the angled links when cornering.
 
Check CCRs website or Speedways, they had the info in their plans and catalogs.
 
If a Panhard will only move the rear by 1/10" horizontally that would be fine. Watts are OK too, but with the limited travel of our rears it isn't critical. But I would keep the bars close to horizontal. If you do a little mockup with cardboard you can see how the mount positions can hinder movement if they are way high. And there are videos on YouTube that sorta explain things. There is also the Mumford linkage:
mum16.jpg

...and the little-known but very slick Rulo Linkage:
P1030790.JPG

Now aren't you glad you asked?
 
Hi AltBantam
Your theory about the Watts links is correct I reckon.
Watts links move the axle in a gentle S movement. They do not keep the axle at chassis 0 through a full suspension movement.
If crank is mounted to axle housing vertical and links are parallel….dependant on which way links go when you depress suspension axle will move + to left. Lift suspension above 0 point axle will move + to the right…a slight S
In performance cars you can mount crank to either axle or the chassis. You can tune over or under steer dependant on setup.
For 2-1/2 “ travel you would only notice S movement with a dial gauge.
Panhard is easier and you can get real creative with its shape and where it mounts.
 
My first Panhard:
farsi panhard.jpeg
It spells Bite Me in Arabic. Didn't go over well in the Mideast...
 
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Neddo, I thought about the lower diagonal bar before, but I have read they're good on the track, not so good on the street. Of course there are always variables to consider... PotvinGuy, it seems I will be sticking to my original idea of using the panhard bar. I will tack weld the mounds and double check for interference with a floorjack. I need to mount the bar in front of the rearend, like the Speedway carrier mount, but will weld the mount along the axle tube. Btw, if anyone is interested and this may have been posted before,
but Airsuspensionbook.com/calculators/ has a calculator to determine the amount of movement caused by a panhard bar. At 33", the movement apparently called sagitta, is .09" The 20" panhard bar Speedway Motors sells is .16". This is with 5" total travel. Add an extra inch of total rearend travel to 6" and the side movement .23" for the 20" bar. At 7", .31". These numbers are with the bar horizonal. Thanks again.
 
Neddo, I thought about the lower diagonal bar before, but I have read they're good on the track, not so good on the street. Of course there are always variables to consider... PotvinGuy, it seems I will be sticking to my original idea of using the panhard bar. I will tack weld the mounds and double check for interference with a floorjack. I need to mount the bar in front of the rearend, like the Speedway carrier mount, but will weld the mount along the axle tube. Btw, if anyone is interested and this may have been posted before,
but Airsuspensionbook.com/calculators/ has a calculator to determine the amount of movement caused by a panhard bar. At 33", the movement apparently called sagitta, is .09" The 20" panhard bar Speedway Motors sells is .16". This is with 5" total travel. Add an extra inch of total rearend travel to 6" and the side movement .23" for the 20" bar. At 7", .31". These numbers are with the bar horizonal. Thanks again.

Neddo,
Most vehicles that ride on coil springs in the rear have to run some type of centering devise. I would think the majority use a panard bar due to simplicity and cost. Works very very well. Up until the new generation NASCAR with the five ling IRS all cars were mandated to run twin trailing and coil springs centered by a panard bar. Newer generation OEM four wheel drive vehicles with coil springs likely are centered with that same style panard bar. Simple, strong and they work. The shop next door to me have two four point lifts and I look at the under carriage of card and trucks on a regular basis. All 1967 -1972 half ton Chevy trucks run the same rear suspension as what NASCAR mandated for so many years.Success speaks for it'self.
Good Luck with your project.
George
 
I thought Vietnam was a nasty country, but the Middle East has them beat, hands down.
:ninja::thumbsup:
 

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