triangulated 4 link help

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brewil

brewil

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Hi everyone
Due to the extreme costs involved (bad currency/shipping/40-60% imoprt charges)
I am going to get a triangulated 4 link made in South Africa where I live.

Im looking for help with bracket templates and top bar angles and any other calculations.
It would be sooooooo appreciated.

Thanks
B
 
What is the car and what wil it be used for? Daily driver? Racing of some type? If so, which type of racing? Not sure I can help any but that is kinda important to know. Opps, Isee this is on another thread.....
 
Not seeing th other thread, so I'll post it here. Search the interwebs for "ExcelCAD", it is a 3/4 link design program used primarily for off-road rear suspensions, but will work for you as well.
 
Looking for a good handling/cornering setup but need templates
For the brackets and angles for the upper rods.
To give you an idea why im doing it here and not buying
The rod kit and brackets in the States:
($350 kit + shipping +/- $75 to $100) + (import duty 25%) + (10% upliftment fee) + (14% VAT)
 
Thanks guys looking at the cad program. Any other tips
Will be greatly appreciated.
 
Jo Diesel said:
Mad Dart has a complete build that is pretty impressive.
http://www.forabodiesonly.com/mopar/showthread.php?t=101437
Click to expand...

That's what I was going to suggest. I actually own that rear now and glad I didn't have to build it. I think he has all the info on how to make it. He's very knowledged and insightful on them and will always help out with advice. You may look at his new setup he's putting in his Scamp too. Not a triangulated setup though. One thing to note, my car was piss poor in the corners and rolled bad with the triangulated setup and /6 bars up front. I had to install an anti-roll bar on the rear to keep it somewhat stable.
 
Art Morrison has a triangulated setup ,even can get a sway bar for it :

[ame]http://www.artmorrison.com/instructions/tri4-bar1-Model.pdf[/ame]



http://www.artmorrison.com/rearclip-tri4bar.php

Not sure those dimensions could be used for a Dana though.

Video on a couple of their setups:

[ame="https://www.youtube.com/watch?v=aO2yva2JvAY"]Break-Down: Art Morrison Camaro - YouTube[/ame]
 
Since you are emphasizing cornering, I would suggest that you study up on rear roll center locations for this design. Triagulated 4 links tned to have high rear roll centers. Look here for the concept: http://cr4.globalspec.com/thread/66877

I would prefer a parallel 4 link with a panhard rod to get the rear roll center lower; the car will be less 'tail-happy'. You can more easily adjust the pivot point on one end of the panhard rod and tune the rear roll center height and thus tune over/understeer.

Thanks for the link to that program, ntsqd; I need to look at that.
 
Cool was thinking of a parallel but thought it was more for drags. The Chargers tend to be light in the tail and slide out.

I spoke to Mad Dart after seeing his work, it was actually the inspiration for what I want to do. The shell of my Charger is on blocks so want to do the rear and then eventually get one of Hemi Denny's k-members after stiffening up the body.

Anyone want to weigh in on the tri-4 link vs parallel with panhard? Curious what peoples
experiences are.

Thanks guys
 
I'll add this comment on the comparison: Any rear roll center height with a live axle is primarily determined by the height of the parts that provide the lateral locating function of the axle. It can be changed somewhat by link angles in a triangulated 4 link but the fact that the angled links are ABOVE the axle automatically moves the rear roll center well up in height. It can be lowered by chagning the links' verticalangles but you can only do so much with that. And, if you reduce the relative angle between the upper links you can lower the roll center more....but if you reduce the relative angles a lot to try to further lower the rear roll center, you lose the locating function and the rear starts moving around a lot sideways under the car. (And, think about it: as your reduce the upper links' relative angle to zero, then you have made a 4 parallel link design anyway!)

The use of a panhard rod instead for the lateral locating fucntion allows to move the rear roll center down a LOT; you can even get it below the centerline of the rear axle. You can add rod end mounting holes and move the rod (and roll center) up and down for tuning. Or use a jackscrew at the chassis end mount if you really want to get wild, like NASCAR. The one fabrication issue to get the rear roll center down low is to make the chassis end mount long and stick down a lot; that takes some fabrication but that has been solved many, many times for racing and production cars. (For a good production example, look under an Opel Manta A or B or the Ascona A or B. (And the Kadett C's also, if I recall right.))

NASCAR has gone this way years ago for this reason. And most or all of the successful RWD, live axle rally cars in the 80's used the 4 parallel link and panhard rod. It does as said with the rear roll center and is rugged. So all that should clue everybody into this concept... for street and track handling. (Roll centers usually become a very secondary thing if drag racing; they can be high or low and not have much or any effect on straight line weight transfer, etc.)

BTW, my racing experience is 95+% in rally, if that tells you anything. Rough surface handling is the holy grail there.
 
Mucho appreciado!

I'll look into the p-llel 4 link.
What if you use a rear sway bar on a tri-4 link though.

Want to test out the options
 
If one of the links in a 3 link is a 'Y' then it's attachment point will be the roll center for that suspension.
If it is not then it needs to be big and have strong mounts because it will be taking all of the torque resisting tensile forces from acceleration. BT, DT with a '60 El Camino street rod powered by a healthy 409.
 
How long is preferable for the third link.
Ive seen some centered and some off centered.

Will the 3 link handle 500hp?
 
Is a 3 link possible without chomping the floor pan?
So third link is 70% the 2 main links. Got that.
 
brewil said:
Mucho appreciado!

I'll look into the p-llel 4 link.
What if you use a rear sway bar on a tri-4 link though.

Want to test out the options
Click to expand...
Does not change the rear roll center, if that is what you are asking. The anti-sway bar can be tunable (as I suspect you know).

The advantage of a lower rear roll center is that there is less inherent weight transfer on the rear to have to control/manage/tune. You're just starting from an better design point for good cornering and end up with fewer compromises/ more flexibility.
 
My take on Roll Center is that the further away the CG is from the Roll Axis the more leverage it has to lean the vehicle in a corner. If the Roll Axis were to pierce the CG the vehicle wouldn't lean in a corner at all. In the front the linkage geometry that defines a desirable camber curve unfortunately places the Roll Center quite low.

If the CG is as low as you can get it then having a slightly elevated rear Roll Center to reduce the distance from the CG to the Roll Axis in the plane containing the CG and Normal to the Roll Axis may not be a bad thing at all.
 
Not sure why my last reply does not show.....IMO, your point is well made. And I should have thought my post out better...

There are other considerations for roll center height that tend to trump the distance between RC and CG. The relative height of the 2 roll centers is very important for a fundamentally good handling car. Successful designs tend to have the roll centers fairly close, which makes the basic chassic/suspension close to neutral in over/understeer. The basic Mopar design if not that way, the front RC is slightly below road level and the rear RC is fairly high above road level. Contrast that with the newer Challegner/Charger RC's' which are pretty close in height; there are plenty of other examples liike this.

Moving the rear roll center down gets them closer in these Mopars, which is desirable. Moving up the front RC would be good too (but that is not the discussion here.) Getting the setup this way and fundamentally closer to neutral steer is, in my mind, kinda like getting the F/R weight distribution close to 50/50; you are just starting from a fundamentally better handling point. Both of the cars I have raced extensively enough to appreciate (Opel Ascona A and Mitsubishi Starion) are both this way; the Opel in particular was a top notch stock road race car out of the box (for handling) in Showroom Stock A. It used a live axle with panhard rod set rather low that set the rear RC low, and the front control arm angles are such that the front RC is above the road surface, rather than below it like the Mopar suspension; the RC height match was much closer and anti-sway bars F/R were used for body roll. (But that same control arm arrangment resulted in poor inside wheel negative camber in cornering; typical production car compromise....)
 
brewil said:
anyone do a 3 ink bar setup?
Click to expand...
Check out my Dart build. I have a 3 link in that. Will add a sway bar later.
The reason 3 and 4 links sway more is you have freed up the rear suspension. Leaf springs do a lot to tie up the suspension so there is a definite need for a sway bar
 
It is not the linkage that does that, it is the lack of internal friction in the springs that subsequently require more damping that does that.
 
aaah that's a torque arm setup!! Nice! Looks well fab'd.

I would like to go with a 3-link, shorter top arm, offset to the passenger (US) side.

Just trying to figure out how to keep the pinion angle from rotating during suspension travel.

How do you work out the angle of the shocks from diff to frame?
 
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