Thread: Four Bar Any Problem ??

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Hey guys take a look at this four bar set-up and tell me if you see a problem with an "ALL" trangulated 4 bar system.

RS

I'm not an expert on 4 bars, never used one, but aren't the front pivot points supposed to be directly in line with each other so they travel on the same arc with no bind?

Just askin'.

Don

RS, what I see is that as the body moves laterally, either the bars will bend at their attachment points or be broken off completely from their mounts or the bolts will break or the heims will break or the brackets will break or all of the above will happen. As far as how the car would handle if the rear suspension would stay together, I can't tell the angle of the links as you didn't show a photo from the side.

Don, I was taught that if the links are equal length and parallel, like railroad tracks, as viewed from the side of the car, then the system is called 4-bar. If the links are unequal length and at different angles as viewed from the side, like on a purpose-built drag car, then the system is called a 4-link. A 4-link would be adjustable for squat/rise, whereas a 4-bar would not.

If we assume that the longitudinal center of gravity is at about where the camshaft would be in a pushrod-V8 car, then we would draw that line horizontally from the centerline of the front tire to the centerline of the rear tire. Generally, this would be about 24 inches from the ground. Now, we would draw a line vertically through the center of the front tire and place a dot at the intersection of the two lines. Now, we would draw a vertical line through the rear tire and place a dot on that line about an inch below ground level. Now, connect the dots with a diagonal line. This is your anti-squat/anti-rise line. Now, extend a line through both suspension links out to where they meet to form an instant center (IC) at the anti-squat/anti-rise line. If the IC falls above the asar line, the rear of the body will rise on launch. If the IC falls below the asar line, the rear of the body will squat on launch.

If that were my car, I would install a Panhard bar. I hate 'em, but if you build 'em right and install 'em right, they work pretty well. Please read through my post #30 on this thread....
http://www.clubhotrod.com/forums/sho...panhard&page=2

With the attachment points that far out and with no bush movement it would be more like a anti roll bar, I wouldn't give it long

Thanks guys!! I am in the process of doing a new build, and was searcing thru a different Forum's build thread's when I came across this idea and this photo. I do not want to run a Panhard Rod as there simple is not very much room and a panhard bar even makes running the exhaust much worse. I am going to run a 4 Bar or Link or something and run two of the bars triangulated to avoid using a Panhard Bar or even a Watts Linkage.

Don, You know until you pointed that out I didn't see that problem. After studing that photo it is pretty plan that any suspension travel to speak of and something is going to either Brake, Bend or Mutilate itself to death.

Tech, God bless you man once again I complettly fail to understand what you are saying, maybe thats because its very late, or I'm just to dumb and have fried to many brain cells to comprehend. But thanks Dude maybe tomorrow after I get up and reread that it will become clear----I Hope!!

Roland

Originally Posted by Hombre259

I do not want to run a Panhard Rod as there simple is not very much room and a panhard bar even makes running the exhaust much worse. I am going to run a 4 Bar or Link or something and run two of the bars triangulated to avoid using a Panhard Bar or even a Watts Linkage.

That's why I went back in the archives and found the thread I linked. If you will scroll down to post #30 like I said here, you will see in the drawing that I included there, that the Panhard bar can be any shape or twisted up like a pretzel to miss components. All you have to do is make the two attachment points the same distance from the tarmac, make the bar as physically long as you can (brake drum to brake drum) and make it from material that will stand up to the form you construct (make it stiff).

I don't really see the setup in the picture working very well or for very long... I prefer the triangulated 4 bar with the bottom bars parallel with the frame and the top bars angled in...takes up a bit of the exhaust room, but still not too tough to work around it...

Originally Posted by Hombre259

Thanks guys!! I am in the process of doing a new build, and was searcing thru a different Forum's build thread's when I came across this idea and this photo. I do not want to run a Panhard Rod as there simple is not very much room and a panhard bar even makes running the exhaust much worse. I am going to run a 4 Bar or Link or something and run two of the bars triangulated to avoid using a Panhard Bar or even a Watts Linkage.

Don, You know until you pointed that out I didn't see that problem. After studing that photo it is pretty plan that any suspension travel to speak of and something is going to either Brake, Bend or Mutilate itself to death.

Tech, God bless you man once again I complettly fail to understand what you are saying, maybe thats because its very late, or I'm just to dumb and have fried to many brain cells to comprehend. But thanks Dude maybe tomorrow after I get up and reread that it will become clear----I Hope!!

Roland

you do not need the upper bar if the springs are used.but if your using the bags? if yes to the bags then i would use a real four link and you would need a track bar .pan hard .or watts . less you triangulate the bars like Gm car or ford did it. then a track bar is not needed. if you use the stock springs and use a four link .or ladder bar then you should float the rear axle .all points for bars are base off the crank center line were i am from .more or less whats in the photo is a 1/2 ass ladder bar set up . the raise and fall of the rear axle is some what linear as if you hit a pot hole it will not move one side but the complete axle where there is some bind and good strong mount points are needed to deal with that..... but its not bad but not the best for ride were a 4 link may ride abit better but with a solid back axle its only going to get so good. i built them both ways with ladder and four links .my chevy is about the same set up as any car leaf spring car.i have floater i made many years ago moved the springs under the frame and used comp ladder bar s i had the car stock and the way it is now the ride is not that bad as some would think still better then many hot rods when you float the spring s you should use a track link bar of some kind to keep the rear axle from moving side to side as you do not clamp on to the spring over the center bolts with u bolts to hold the axle to the spring so you can get some side to side movement. SO why they have it set up like this in photo ? they do is for the bags as the upper bar having its owne mounting point will bind for the lower ride deal .i built mine for alot of power only...getting the spring eyes getting pulled out and spring whined up. pinion climb can be a very bad thing