Anyone running a 3 link rear supension on their rod? After reading a dozen plus web sites on 3 link truck and racecar setups, is there anyone using this system on their car? I like this setup. I plan to change my bad early Ford radius rod two bolt on the bottom of the rear suspension to a 3 link no binding better on the road rear suspension. Three 1" x .156 x 30" tubing with heavy duty heims on either end and either a panhard (which I alreay have) or watts link in the rear. I think I'm going to take the old ford rods and cut, clean, coat against rust and slip them over the bottom two rods then weld then on so the bottom looks old school. What y'all think about that?
Yes, it works great..........that way my ass resides where other cars have their radius rods........so I can sit in the car, and not on top of it.
Mine's similar to a 3-link, I guess you could call it a wishbone. I have lower control arms mounted from the bottom of the axle to the outside of the frame. On top I have a triangular shaped wishbone with the base of the triangle attached to two points near the top of my kickup and the apex of the triangle mounted to the top of the rear end. It works great, bind free and doesn't allow for any lateral movement of the rear end. Its the only thing that works for me, the car is about 5.5" off the ground and heavily chanelled.
made these for lower control arms. http://www.jalopyjournal.com/forum/showthread.php?t=74337&showall=1
Works great, I love mine. I started out with a four link but changed to a three link better, tighter choice.
I've built 2 street cars after running one on the dirt tracks for years. Use the longest panhard bar you can unless you use a buggy spring, which doesn't need one. Mount the top link as close to the center as possible. Longer the better on lower bars. Somewhat narrower front mounts than rears seems to help. Because the three rods pivot on all 6 ends, the bars are only subjected to push and pull loads only and massive bars are not nessesary but frame mounting points need to be substantial. Bar length and angles need to be thought out because this set up really works and will work either for you or against you.
That looks sturdy. I'm courious, why not do a triangulated 4 link? It seems simpler and lighter. Is there an advantage to the 3 link? I know there's more than one way to skin a cat. Most times one's just as good as another. Was it just easier to build that way? Educate me - I haven't built anything yet. I've only looked at pictures and collected a pile of parts in the back yard. I'm hoping you know something I don't and will spill.
A properly designed three link wil have no bind where a 4 link must have some flex points unless you always only go straight.
Im surprised no one has gave you shit about the buggy spring and panhard rod ? Hell i never used pan hard rods with buggy springs front or rear years ago .. then the smart fellas ??? I think its a money deal.. Ha Ha Dave
On my modified, the lower two bars run under the frame rails. The upper center bar runs next to the drive shaft, in the tunnel. It is the same length as the drive shaft, and mounts near the transmission tail shaft, so it swings the same arc. I also use a panhard bar for lateral control. With this rear end set up, it allows the seats to be between and below the frame rails and the drive shaft. I'm 6' tall and my buddy Wes is 6'- 2" and as you can see we sit quite low in the car! - Dennis
If you look through my posts, this was the topic that I struggled with the most during my build. This ended up being the fourth suspension design. I was going to go with a four link but the center section on a 9" isn't centered so I was going to have to come up with different height mounts and trying to keep all the respective angles was driving me crazy. fab32, my hotrod Yoda came over and said "Why don't you build a wishbone?" He drew it up on some cardboard and I got to cutting and welding. You could even turn around the design and put two mounts on top of the axle and one in the center of the chassis. I have rod ends at all pivot points including the top of the rear end. This allows me to change the pinion angle.
It's great to see many 3 links out there. A couple of questions though... I see most of you have shorter top links, being shorter than the bottom will cause the pinion angle to change. Won't this be a problem or is the change not enough to make a difference. How do you calculate the proper lengths if the top and bottoms bars are different? Also, panhard or watts links with buggy springs? I'm using a buggy spring set-up similar to the 40's fords, spring behind the rearend. I've read both that you should still use one a panhard or watts and also as written above that the buggy spring itself holds the rearend in place. I've also read that it doesn't matter either way because the shackles will limit any binding caused by a panhard bar, etc. What are your thoughts?
I set my car up with just under 4" of travel but I don't think its even close to that. I was under it yesterday to check things out, the rear has not touched the frame above it. The weight of the car(or lack there of in my case) and the stiffness of the springs both limit the movement of the rear end. If you look at the design of many pavement latemodel stock cars you'll find a similar design. Some have long lower control arms almost extending to the main hoop area on the outside of the chassis and a small adjustable mount maybe half the length of the control arms on top of the rear end. The rod ends allow the rear axle to "float" and maintain a reasonable pinion angle as the suspension goes into compression.
The shackle arc will limit the side sway with a buggy spring but if you run a panhard bar it will take over control until something breaks and then the shackles and spring will do the controlling as the broken pieces drag down the road. The shorter top link will cause the pinion to rise and fall through suspension travel but thats a geometry thing. Ed Howe was the brains of 3 link circle racing back in the 70's. What I liked about it was that it could be adjusted to do about anything including steering the back of the car and it could be adjusted to changing track conditions. Supposedly its obsolete now on dirt.
The links travel in arcs. For the sake of learning, lets say the bars are level. As you hit a bump the suspension moves up putting angle in the bars. That point just moved forward in the car. With a four bar as you turn, let's say left, the right side bars are going up and the left side bars are going down as the body rolls. Now you have one side of the car trying to twist the rear one direction while the other side of the car is trying to twist it the other. On a street four link the mounts on the rear are normally welded to the axle tube so there is a huge bind. On our race cars the four bar mounts are mounted to bird cages that allow the axle tube to rotate inside the birdcage so there is no bind. Rear end wrap is then controlled by a torque arm or what would be the third link on a 3-link suspension. A good way to see how your suspension is going to work plot your suspension points to scale on a piece of paper then use a compass to mark the path that each link will follow as it goes through suspension travel, you will be surprised at how much your rear is going to move fore and aft. The shorter the rod length the more radical the arc. With the 3 link you don't have the top link fighting the top link on the other side of the car, so the rear is bind free. You can get a bind if a 3-link if your top link only allows up and down travel. My first third link was designed for an asphalt car with long arms. It didn't allow for the massive rear steer that my 14" arms generated. Once I'd hit the apex it was like the steering wheel was locked until I hit the straight and the body leveled back out. I replaced the third link with one that had a heim on the end and now it's like I have power steering. The anlge of the rods also generate traction. For a street car you'd want them running close to level. When I first started racing a driver once explained it to me this way. Imagine you are standing on a scale with your arms level push on the wall in front of you and the numbers on the scale don't change. Next put your hands higher on the wall and push again. The numbers on the scale are now going up. It's the same with upward bar angles, when you step on the gas the rear pushes forward using the bars to try and pick the car up. Too much angle you'll feel the car lift as you accelerate. Actually it feels pretty cool to feel the rear stand up then sit back down as you get on and off the throttle, but it's not real streetable.
Is there an optimal length for the lower and upper arms? Or are those "optimal lengths" related to some other measurement(s)? Is there an optimal height difference between the upper and lower arms? Thanks, gary
It's what fits. The longer the rod the less of a arc the rear will move during suspension travel. Too long and it will look like hell though. The top link controls your rear end wrap. Angled down to the front it will try to lift the body under acceleration planting the rear. The longer the rod here the more consistent handling the shorter the more it lifts. Unless it's mounted level that is. I ran one for a short time that was around 18" with 15 deg. of angle and it really stood the rear up when on the gas, but it really unhooked the car when I'd lift to set up for the corner. What benefits one end hinders the other end. My current third link is approx. 4' long and mounts between the transmission and the front of my seat, but I don't have any passengers. The picture a few post ago of the triangular top link will do double duty as the panhard bar and third link, but I'm curious as to how it drives while accelerating or braking on rough surfaces. It's mounted level so it shouldn't affect traction under acceleration, but being short so short it should really tweek pinion angle during suspension travel. On a street application I doubt if you'll notice the rear steer if you have to go to shorter arms due to the limited travel it will see. My arms are mounted at a fairly steep upward angle. When it rolls over in the corner it levels the right side out pushing the RR back approx. two inches and the left rear sucks forward even farther gaining even more agle. The LR moves forward approx two inches also giving me close to 4 inches of rear steer. It's a fun ride!
I built a 3-link for my Henry J. I designed it to give good hook-up on the track plus a smooth ride. 28,000 miles and many strip passes and it performed perfectly. I modelled it after the Buick GNX of the 80's (the new Mustang is similar). The center link runs parallel to the driveshaft and (in my case) was 28" long. I welded bosses to the 9" rear for mounting it. The arm goes on the right side of the driveshaft to correctly react the torque. I used late model mustang lower control arms and springs. I laid out the pivot points on CAD so that there would be no binding through the full travel. The suspension was also designed so that the instant center would be forward and below the car's center of gravity to plant the rear tires on acceleration. I used a simple panhard rod, as long as possible given the available space, and a shortened Mustang GT sway bar. I think I had all of $200 bucks into the suspension. PM for pics if you want to see what it looks like.
you know, it just seems that every time i'm going to ask a question about something around here it gets answered before i can. i have been toying with different ideas to use on my frame i'm putting together and don't like how most things look. i love the 3-link setup and my frame is already setup perfectly to put that in with very little modification. does anybody have any more detailed pics or possibly sketches or schematics of 3-link systems?
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