Anybody use this 4 link software to design their suspension. I found it on another forum and it seemed interesting. I am no 4 link expert so I was wonder what others thought of it. Also attached is an odd looking 4 link setup apparently conceived by using this software somehow.
I believe it is for a 60's Cadillac. The guys wants to run it low and use a 4 link setup with minimal floor pan intrusion...
Jeez the specs on that shot are virtually identical to my 47 Roadmaster. For once happy I am not as far along as I had planned. This should link to the program and you need excel to run it http://mysite.verizon.net/triaged/files/4BarLinkV3.0.zip
Some good (and bad) info on 4 link set ups here: http://www.jalopyjournal.com/forum/showthread.php?t=791399
Well, see you should have. Because that setup you posted above is another example of function following form... Yes, it WILL hold the axle under the car, no arguments there. BUT, the top links are below the axle centerline, which puts M***IVE leverage against the lower links under hard acceleration. That, and the fact that the entire ***embly is hung off a single round tube crossmember make it kinda scary. If the intended use is ONLY "low and slow", no problem. As a ch***is builder and teacher, I always worry about what happens when someone ELSE buys the car and doesn't understand the limitations of the design...
Yes, although I am no expert it just seemed to go against stuff I had come to know was correct. Looks to be a good idea but just hard to see how it was right!!!
The software he used to design it might be right on the money...but it seems like all thought and effort went to constructing it "light and delicate" as opposed to "strong and tough". In a street suspension the latter is whats important. For me...that setup is way too light duty for a Cadillac.
why not give credit to the Pirate4x4 poster who created the software? like others, i thought the design of the caddy suspension was questionable, but upon some thought, the fact that the links are all below the axle really should have little negative affect as long as the fab work is done well, and it looks ok from the pic. i'm giving the builder the benefit of the doubt, and ***uming that the tube that the links are mounted to will be braced, gusseted, etc. after mockup. back to the axle/link relationship...knowledge gleaned from the offroad world says that that suspension will work just fine. look at a Mercedes Unimog, they have portal axles. look it up if you don't know what they are. you'll see that as far as suspension forces are concerned, this is basically what a 4 link would look like applied to a 'mog, but upside down. i'd be curious to see what it looks like run through FEA software, but i'd take a WAG and say that this setup would stress the links and mounts only slightly more than than a typical 4 link would. i've always used the truck-arm style of 2-link to get low and have a back seat, but i'm going to give this some thought for the future. while i like the truck arm setup, it compromises perfect suspension geometry and traction, but you get an almost foolproof setup with predictable handling.
As I mentioned above, the only problem with it would be under hard acceleration. As positioned, the upper links have zero leverage to resist "axle wrap", unlike they do when typically mounted above axle centerline. Since there is no direct resistance from the upper links, the fulcrum point now transfers from axle centerline to the "upper" link bracket bolts. Because these are below center, the force against the (long!) lower brackets is now being increased, rather than reduced. A quick ****ogy would be like using a breaker bar to loosen a lug nut while the tire is off the ground. If you have the bar sticking out toward the edge of the wheel, it's very hard to keep the whole tire from spinning, because your leverage from hand to socket to hub is multiplied against the wheel bearing. That would be both sets of links below axle centerline. If you cross the bar over the spindle however, you have the same force against the nut; but it's much easier to hold the tire, because the leverage at the bearing is greatly reduced. This would be a typical setup, where the axle centerline lies between the upper and lower link brackets. Hope that made sense...and it really doesn't matter anyway.
Here is another pic of that different 4 link setup. Those lower arm brackets must run pretty close to the road...
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