akitagandy
Member
Is there a min,max measurement between rear radius rod brackets that weled to the rearend , The frame is 26 1/2 wide,I am building from Spirit plans
radius rod brackets on rear end
- Thread starter akitagandy
- Start date
norseman
Member
I dont think there is a min max measurement. BUT your radius rods need to clear the bottom edge of the body so it would be a good idea to have a body handy. I would err on the side of being wider. In the world of car geometry things were meant to swing around centerlines. If you were standing behind your car in a perfect world the lines formed by your radius rods would come to a point somewhere about in the middle of the car, that would let the rear end pivot around the centerline without binding up. Same way for front radius rods. The more paralell they are the less efficently they work. ford had the fronts come right to a point on the centerline aka the "wishbone"..In t bucketworld the suspension really doesnt travel that far so we can get away with things that would cause a guy who builds rock crawling 4x4s cringe....Good luck!!....
Ted Brown
Member
Now it also depends on a big IF, you are lookin to get traction, then lift type radius rods are in order, and here is where big rubber bushings come into play, to help with the binding when the car leans in street driving, as the radius RODS are trying to twist the rear end housing when ever you go into a driveway at an angle, or the car leans in a corner... Now IF you want ride and are not worried about a race car start, and want smooth, non binding cornering, a 4 bar set up is now for you... No matter how wide you make your rods mount to the rear end (what looks best to you) make sure the mounting bolts are all square with the rear axle... a good amount of suspension travel is what you are looking for, remember leverage is the KEY to all things home built... VERY IMPORTANT, forgot to mention, when using Heim joints with either 4 bar link rods, or even with lift type rods, make sure the mounting bolts are square with the link rods, not the frame or the rear end, just the link rod itself, as this will eliminate side stress.. If the mounting bolts are square with the frame, and the link rod is not square with the frame, that is mounted wrong, as that will give side stress to the Heim joint... Hope that is clear
as mud?? hehe
as mud?? hehe
fluidfloyd
Active Member
norseman Ive ben contemplating switching from my radius rods over to an uneven 4bar setup. I think it would make a very noticeble improvement in my ride..
Norseman,
Before you jump into an uneven 4 bar you need to think about what you really want to do. If you just a looking for a nice ride then make the upper and lower link the same length and keep them parallel. If you want to do a little drag racing then keep them equal or close to equal length and angle the top one down. By keeping the bars an equal length you reduce the amount of pinion angle change as the rear housing moves up and down. Just think of a front arm system with a short upper a-arm. As it moves up and down it creates camber change. If you really want to design it for maximun drag dracing, there is a set of math rules to work it out. Just let me know and I'll be glad to help you out. Have fun.
George
Norseman,
Before you jump into an uneven 4 bar you need to think about what you really want to do. If you just a looking for a nice ride then make the upper and lower link the same length and keep them parallel. If you want to do a little drag racing then keep them equal or close to equal length and angle the top one down. By keeping the bars an equal length you reduce the amount of pinion angle change as the rear housing moves up and down. Just think of a front arm system with a short upper a-arm. As it moves up and down it creates camber change. If you really want to design it for maximun drag dracing, there is a set of math rules to work it out. Just let me know and I'll be glad to help you out. Have fun.
George
Ted Brown
Member
Just remember, there is no lift with any 4 bar set up.. Lift means planting the tires into the ground by lifting the whole car, not waiting for the chassis to settle down... If it squats, it is slower out of the gate, but you are not building a drag car, this is suppose to be a fun cruiser, and a looker, not a headache...
fluidfloyd
Active Member
[Ted Brown]; Just remember, there is no lift with any 4 bar set up.. Lift means planting the tires into the ground by lifting the whole car,
Ted,
Not sure what you mean by "lift." I can tell you this, every Pro Stock drag race car in the country runs a 4 link suspension with the top bar angled down. This projects a pair of lines forward of the rear axle centerline to some predetermined point known as the IC or instant center. This point is where the lifting force will try to plant the rear tires by lifting the car. It is determined by driveline torque, wheelbase, weight and center of gravity and nuetral axis. The more available torque, the longer the IC. These cars all have a number of adjusting holes to change the location of the 4 link tubes in order to best optimize that magic "sweet spot) IC. Along with these forces there are also rotational torque loads trying to roll the car around the drive shaft. These cars carry very large (stiff) diameter anti roll rars in the rear to help launch the car and keep both tires planted evenly. The IC point can be moved rearward or forward and vertically up or down by changing the angles of the upper and lower suspension links. If you have a 2400lb car then you ideally want to lift the car at launch and put 2400lbs of down force on the rear tires. These systems are built very strongly as are the chassis so as to resist any flex or torsional twist as they launch. This also requires very stiff rearend housings as shown below. I have included several pictures of a 4 link system I build several years ago. This is actually a lite weight altered car but the rear layout is the same. I just didn't have any digital pictures available here at the house. I am starting a new car in a few weeks and will be glad to post pictures of that suspension system at a later date. I have also included pictures of a Pro Stock housing so you can see how stiff they are. The super gas housing is designed to run in a less powerful car and weight is more of an issue. That housings is anound 30lbs. The Pro Stock unit is around 45lbs. If anyone would like to discuss 4 link suspension any further then please let me know. I hope this clears up any confusion as to 4 links, 4 bars and lift. I hope this will be of some help to some of you.
George
prodesigns1@yahoo.com
Ted,
Not sure what you mean by "lift." I can tell you this, every Pro Stock drag race car in the country runs a 4 link suspension with the top bar angled down. This projects a pair of lines forward of the rear axle centerline to some predetermined point known as the IC or instant center. This point is where the lifting force will try to plant the rear tires by lifting the car. It is determined by driveline torque, wheelbase, weight and center of gravity and nuetral axis. The more available torque, the longer the IC. These cars all have a number of adjusting holes to change the location of the 4 link tubes in order to best optimize that magic "sweet spot) IC. Along with these forces there are also rotational torque loads trying to roll the car around the drive shaft. These cars carry very large (stiff) diameter anti roll rars in the rear to help launch the car and keep both tires planted evenly. The IC point can be moved rearward or forward and vertically up or down by changing the angles of the upper and lower suspension links. If you have a 2400lb car then you ideally want to lift the car at launch and put 2400lbs of down force on the rear tires. These systems are built very strongly as are the chassis so as to resist any flex or torsional twist as they launch. This also requires very stiff rearend housings as shown below. I have included several pictures of a 4 link system I build several years ago. This is actually a lite weight altered car but the rear layout is the same. I just didn't have any digital pictures available here at the house. I am starting a new car in a few weeks and will be glad to post pictures of that suspension system at a later date. I have also included pictures of a Pro Stock housing so you can see how stiff they are. The super gas housing is designed to run in a less powerful car and weight is more of an issue. That housings is anound 30lbs. The Pro Stock unit is around 45lbs. If anyone would like to discuss 4 link suspension any further then please let me know. I hope this clears up any confusion as to 4 links, 4 bars and lift. I hope this will be of some help to some of you.
George
prodesigns1@yahoo.com
George, (fluidfloyd)
You do some beautiful work. You obviously know what you're doing. I wish that someday I can TIG weld like that! Thanks for the writeup. I hadn't really thought about it much, but the way you described how the four bar works, it makes sense. Again, beautiful work.
David
You do some beautiful work. You obviously know what you're doing. I wish that someday I can TIG weld like that! Thanks for the writeup. I hadn't really thought about it much, but the way you described how the four bar works, it makes sense. Again, beautiful work.
David
Martin
New Member
Beautifull work, very cool pictures!! I love looking at that kind of stuff, and I dont doubt the science behind it, but the world of Pro Stock drag racing is a long way from the world of the owner built T bucket. I suspect that Teds' comments were more in the context of whats available through the Speedway catalog, or what the typical owner builder is liable to fabricate at home.
fluidfloyd
Active Member
Martin,
Thanks for the comments. And yes, you are right about drag racing as compared to hot rods. I only meant to show the negative side of running a short upper bar and the pinion roll it causes. The subject came up and I felt it needed to be discussed. Coupled with a short driveshaft as most of these cars have it does cause accelerated u-joint wear and possible vibration. Most hot rod and OEM suspensions are a compromised design and work great. But if you are going to inject street/drag race into the car then these basic design princples still apply.
Now, about your ride. Truly a beautiful piece of work. I can't nail two boards together. But anyone who can do automotive wood work...well they are master craftsmen. My hat's off to you sir.
George
Thanks for the comments. And yes, you are right about drag racing as compared to hot rods. I only meant to show the negative side of running a short upper bar and the pinion roll it causes. The subject came up and I felt it needed to be discussed. Coupled with a short driveshaft as most of these cars have it does cause accelerated u-joint wear and possible vibration. Most hot rod and OEM suspensions are a compromised design and work great. But if you are going to inject street/drag race into the car then these basic design princples still apply.
Now, about your ride. Truly a beautiful piece of work. I can't nail two boards together. But anyone who can do automotive wood work...well they are master craftsmen. My hat's off to you sir.
George
Ted Brown
Member
4 rods that have a pivot at each end, can not LIFT, without them being able to lift, it does not act as quick, BUT, with todays tires, the cars probably do not need that much instant traction, and they are easier to load the rear tires... I have built MANY AG/Super cars, and I have tried them all... a 4 bar setup lets the chassis twist, without changing rear tire weight as much... So it is easier to make them go straight...
a 4 bar setup lets the chassis twist, without changing rear tire weight as much... So it is easier to make them go straight...
Brucer
New Member
in my redneck way of things,
what a 4-link set up does is change instant center.... moving it forward of the actual center of the vehicle... you can make it 10 ft in front of the vehicle if you want..
same as a ladder bar, except a 4-link does it even more drastic and is alot more adjustable... a 4-link actually plants the rear harder. basicly stabbing it into the pavement.. it does this due to the hinge point it creates with the angle and uneveness of the bars.. when the rear torques it throws the rearend into a rotation, and that makes the 4-bar throw the rearend down into the pavement..i guess they call it articulation..
a ladder bar setup stabs the rearend into the pavement due to its front mounting point..
i will usually set a 4links top bar at 10-15 degrees, and leave the bottom bar horizontal or up 3 to 5 deg. as a start point..
what a 4-link set up does is change instant center.... moving it forward of the actual center of the vehicle... you can make it 10 ft in front of the vehicle if you want..
same as a ladder bar, except a 4-link does it even more drastic and is alot more adjustable... a 4-link actually plants the rear harder. basicly stabbing it into the pavement.. it does this due to the hinge point it creates with the angle and uneveness of the bars.. when the rear torques it throws the rearend into a rotation, and that makes the 4-bar throw the rearend down into the pavement..i guess they call it articulation..
a ladder bar setup stabs the rearend into the pavement due to its front mounting point..
i will usually set a 4links top bar at 10-15 degrees, and leave the bottom bar horizontal or up 3 to 5 deg. as a start point..
Ted Brown
Member
George you show me a pic of the (rear) tire gap (either the body raises or squats down) when leaving the line, if it is a greater (higher) gap, not less, then I will eat my words, if the body sets down on the tire, this is what it is supposed to do with a 4 link, as it lets the body do it's thing, without disturbing tire traction, correct??? I would love to see a 4 link lift anything (at the rear end), and the front end, does not count... Look at a dragster chassis, with plenty of HP even they lift the front end.
Look at a dragster chassis, with plenty of HP even they lift the front end.
T4TWO
Member
OK, I got a question about the length of a radius or hairpins. Speedway catalog has them at 32". Nothing shorter or longer than 32".
Say you found dead center point on your frame, and you wanted to install one bracket for both front and rear hairpins/radius bars. You measure the distance and lets just say its 48" from center to either end of the frame. What would the pro's/con's of a longer/shorter hairpin/radius bar be?
The radius bars I have now that came with my bucket measures only 13". Its way to short. So, I'm going to attemp to make a pair myself. IIRC the type of tubbing used is called "dmo" or was it "dom"? I think it was "dmo"
Was thinking about welding in a 6-8" L, 1/4" T, 3" W plate along the outside of the frame with two holes to connect the front and rear bars. Or how about mounting it about 6" towards the rear end?
Any help will be appreciated. Scott
Say you found dead center point on your frame, and you wanted to install one bracket for both front and rear hairpins/radius bars. You measure the distance and lets just say its 48" from center to either end of the frame. What would the pro's/con's of a longer/shorter hairpin/radius bar be?
The radius bars I have now that came with my bucket measures only 13". Its way to short. So, I'm going to attemp to make a pair myself. IIRC the type of tubbing used is called "dmo" or was it "dom"? I think it was "dmo"
Was thinking about welding in a 6-8" L, 1/4" T, 3" W plate along the outside of the frame with two holes to connect the front and rear bars. Or how about mounting it about 6" towards the rear end?
Any help will be appreciated.
Scott
Ted Brown
Member
I use 3/8" plate min. for any suspension mounting brackets, as i only use 1 bracket, and then I even weld a short tube to that, to hold the radius rods away from the frame and body.. Yes a bit (6 inches) is fine closer to the rear end, that will make your bars nice and long, but keep them plenty strong, use a heavy wall DOM 1" x .188 wall or as RPM used .200 wall or so.. :} good luck with your build.
fluidfloyd
Active Member
Brucer, in my redneck way of things,
what a 4-link set up does is change instant center.... moving it forward of the actual center of the vehicle... you can make it 10 ft in front of the vehicle if you want..
You are right on the money in your thinking as to how 4 links work. You must either build or race door slammers. That's good to know my friend. What part of Western Kentucky are in?
George
what a 4-link set up does is change instant center.... moving it forward of the actual center of the vehicle... you can make it 10 ft in front of the vehicle if you want..
You are right on the money in your thinking as to how 4 links work. You must either build or race door slammers. That's good to know my friend. What part of Western Kentucky are in?
George
fluidfloyd
Active Member
Ted Brown, George you show me a pic of the (rear) tire gap (either the body raises or squats down) when leaving the line, if it is a greater (higher) gap, not less, then I will eat my words, if the body sets down on the tire, this is what it is supposed to do with a 4 link, as it lets the body do it's thing, without disturbing tire traction, correct??? I would love to see a 4 link lift anything (at the rear end), and the front end, does not count... :lol: Look at a dragster chassis, with plenty of HP even they lift the front end.
Ted,
First off I guess I don't really understand what your idea of lift is. If you would explain how you discribe lift then I would be happy to discuss this issue. I would like to know if you consider a ladder bar or hairpin a lifting devise? I will still be more then glad to explain my thinking but you will have to wait until next week. I am on a slow dial up connection today and I'm about to leave town shortly. But when I get back I will present my case. Thanks for your response.
George
Ted,
First off I guess I don't really understand what your idea of lift is. If you would explain how you discribe lift then I would be happy to discuss this issue. I would like to know if you consider a ladder bar or hairpin a lifting devise? I will still be more then glad to explain my thinking but you will have to wait until next week. I am on a slow dial up connection today and I'm about to leave town shortly. But when I get back I will present my case. Thanks for your response.
George
Similar threads
