Roll Center location of a Watts Linkage

[sled_dog]

Anyone know where it is? My guess was the linkage center pivot point, my teacher agreed but wasn't 100%, material online seems to say the samething. I'm trying to figure it out because I found a cool setup for 67-69 F-bodies that uses a Watts Linkage and what appears to be cantilevered coilovers but the Watts Linkage mounts to the bottom of a Ford 9". Seems like this would be a really crappy roll center location even on a car. Neat setup though.

http://www.uniqueperformanceproducts.com/CoiloverSuspension.aspx click on the rear coilover one.

With the Watts linkage on top of or behind the axle I think this could be a good setup in a street/corner burner car. Namely make a nice donut car with the great side to side stability. Just thinking about the 69 Firebird dad has sitting in the driveway but never does anything with.

 

[84k5]

link is no good.

 

[sled_dog]

try now

 

[79k20350]

but the website says its the best the the rol center must not matter

 

[ntsqd]

If the bellcrank is mounted to the axle housing, then the Roll Center is the bellcrank pivot point. I believe Fred Puhn's Handling book illustrates it.
I think it is still true when the link ends are mounted to the housing and the bellcrank is mounted to the chassis, but I am not sure. The second mounting method isn't as common.
What happens when laid flat like in your link and the early Matkins Heep frames twists my brain and makes it hurt, but I don't expect that it matters.

Downside to a Watts link is the travel path is "S" shaped. With the right ratio of bellcrank length to link length you can get a pretty verticle middle of the path, but such geometry tends to put the lower link pretty low, even for a street car.

See what you can dig up on Allan Staniforth's "WOB" link. More potential, and more ground clearence.