Thread: Installing a triangulated 4 bar. Need help

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Ed, you need to drop the torch and step back to get a look at the big picture. It is not the suspension which must yield in order to get everything to work, but the frame. Cut the offending frame members out of the way, as well as any offending sheet metal, then re-engineer that part of the car when you have the suspension working correctly.

When a car is built from scratch for instance, all the components are placed where they will work with each other, then the frame is fabricated in order to attach all the components and hold them in place. Not the other way around.

All my books are in storage and I can't repeat the principles from memory, but a short search turned up this explanation for placement and operation of a four bar / four link by Billy Shope on Hotrodders.com:

First, a distinction between four bar and four link:

The 4bar is a parallel link arrangement where brackets at both ends force the bars to remain parallel at all times. The front bracket might be adjustable...up and down..., but the bars themselves are always parallel. With a 4link, the individual links can be adjusted, so that the link pair...on each side...is not necessarily parallel.

And then an explanation of the setup:

With a 4bar and the links parallel to the ground, the squat on launch is excessive. By angling a 4bar up until the bars are parallel to a line...as viewed from the side...which passes through the rear tire patch and the intersection of two other lines, one vertical through the front tire patch and the other horizontal through the car's center of gravity, the car will neither squat nor rise on launch.

With a 4link, if lines through the links intersect anywhere on the previously described line (which passes through the rear tire patch), the car will neither squat nor rise on launch.

Now, my take on it:

As viewed from the side, the car's CG if about the height of the camshaft on a pushrod V8. If we visualize that line as being about 2/3rd's the height of the tire, we can do a simple drawing and see the how Billy's explanation works.

Draw two circles to represent the car from the side, making an attempt to keep the size of the circles and the length of the wheelbase representative of your car. Draw a horizontal line through each tire about 2/3rd's of the way up the tires, running from front to back tire and extending past the tires. Now draw a vertical line through the center of the front tire, from the ground to up past the tire. Now draw a line which angles from the intersection of these two lines down to the contact patch of the rear tire. That angled line represents the line Billy is talking about. With a four bar, you want to keep the bars parallel with this sloping line.

What he says next about a four link doesn't make any sense to me. Maybe you can figure it out. That's about all the help I can be for now, except to urge you to buy this book and teach all of us a thing or two:
https://shop.sae.org/servlets/produc...&PROD_CD=R-146

As much as I despise Panhard bars, I may be tempted to agree with Bob on this one. You could run a single top link straight ahead and a Panhard bar to keep the body from swaying on the diff. If you do that, just be sure to make the Panhard bar as long as is humanly possible and mount it parallel with the ground with the car at ride height. It won't matter if you put a few bends in the Panhard, as long as the attachment points are installed at the same height as viewed from the rear of the car.







http://www.progressiveautomotive.com...m/triangul.htm