2-link suspension length?

what........?

 

4 link, yea......The silver Dodge ( diesel, that was bagged all the way around and 4 linked, layed frame when brand new ) had a goose neck in as well that he would pull a 27,000# bulldozer with sometimes....

 

Ditto the Watts Link

4TTRUK

 

I guess NASCAR and Chevy were both wrong. Thanks for the one-sided view. One disadvantage to a 4-link is room! The four-link set-up I had in a different car didn't allow any room for exhaust to run over the rear-end. Another advantage? COST.
Sometimes you don't need to over-design everything. Keep it simple.

 

There are so many BAD design truck arm suspensions out there it isn't even funny.
For starters, the should always be made of and I Beam style design, just like the original Chevy's. This can either be I beam material or back to back C Channel. The reason for this is they need to have some flex or twist to them to allow articulation. Square tubing and Round tubing should not be used. Neither one is the correct application for a twisting motion. This is the reason Chevy did them that way originally and a reason that NASCAR Mandates this design - tubing will eventually fail, or if the tubing is so thick walled as to resist twisting, the mounts will eventually fail!
Next, a threaded joint (heim or otherwise) should never be used in the front mount. because of the nature of the truck arms to try and twist during articulation, a threaded type end will cause the jam nut to come loose and then work the threads back and forth until they fail. Always used a fixed bushing or heim in the front end. If you need adjustment (you shouldn't on the street if you design the parts right), then a slotted mount with adjustment slugs is the best way to do it.
i know guys are going to scream that the have done it this way or that way for years and they work fine Yadda Yaddda yadda, but that doesn't mean that is is good, safe engineering - it just means they got away with it.

 

Finally, somebody gets it. I kept trying to get this across, but I gave up.

It does need to be done this way, or it is just plain wrong.

 

ABSOLUTELY CORRECT !!

I also like to add that 2 links should not be parallel , but point close together as possible at the point of origin.
This allows the front bushings to flex enough to allow some bodyroll.[with the added torsional compliance of the "I" beams ]


A wishbone ["A"frame ] is better, but properly designed 2 link with enough compliance is OK

 

There are plenty of folks out there attempting to, and even succeeding at selling 2-link setups, with non-compliant links. Some even pepper this board regularly with their "ads".

Not one single one of them has accepted my challenge to prove-out, using hard science, that their designs are fully functional, or even safe, over the long-term. I will give you three guesses why.

 

One sided view? ...ok...... The key word was - adjustable.

Trailing arms are not used in NASCAR, or developed for an adjustable set up to get extream amounts of travel than can be obtained w/bags. If all you care about is a non-adjustable suspension that only gets say, 3" of travel up or down of ride height then it's fine.

Also, if Chevy had it so right, and the design was so perfect then why was it discontinued after 1972??

There are tons of ways to set up the bars, top and bottom, so getting room for the exhaust should not a factor.

As for cost, I have never understood why would you want to skimp? I mean why spend all this time, effort, and money on a car only to save a few dollars, just build a suspension that does not perform as good as it could?

 

Lots of good advice above. Truck arm would be my first choice and I would stay with front mount point at u-joint even if I had to modify length of arm and add another crossmember. I would also keep mounting points as close as possible. The truck arms must flex to work correctly as posted above. The factory arm bushing helps with any binding issue. If building your own, it will be difficult to make one that will work as well as the original GM arm.

 

Because leaf spring suspensions are much cheaper to produce than a 2-link system.

GM is a publicly-traded, for-profit corporation, not a cutting-edge engineering charity.

 

They did continue with a variation of this! The Torque Arm used on Gen 3 onwards F Bodies.
They used 2 floating trailing arms each side for Forward location [ and underfloor clearance ]
The torque arm controlled all axle torque from power or braking.

The torque arm or 2 link has a disadvantage of continuous changing pinion angles with changing ride heights .

A cheap form of Drag Racing Ladder Bar that can also go around corners

 

Sorry to bring back an old thread but its the first one I came across when I googled 2-link suspensions so I figured others will probably see it as well. I keep seeing people say the closer the better as far as where the arms attach to the crossmember but how close is too close? Is it ideal to have two seperate arms or would a y-link be even better? There would only be one crossmember mount at that point making it exactly centered.

 

Stefan -

The arms need to "articulate" seperatly, so NO, no connected Y designs. While it "can" be done, like the early Fords, and if you carry out the Chevy design that far, the seperated arms handle much better than a one piece design. Less binding, easier to design and build than a single large...ball joint.
I used the same angle that Chevy used on my 54 Studebaker. While I haven't taken it to the drag strip yet, that is the plan when the hot rod Stude engine is done. But as of now, it rides great, handles as well as a 60 year old front suspension can be expected to. The rear axle is hung by a pair of coil over shocks (heavy, adjustable) in front of the Quick Change housing and has an anti-sway bar.

Mike

 

You can never get "too close"......You can connect the 2 arms into a true V, and have the resulting "wishbone" pivot at one point. You would of course require a locating "watts link" to keep the whole magilla from swaying around. Or, a transverse buggy spring, which basically does the same thing. Basically the best of both worlds, IMO; a fully articulating rear suspension with zero bind, while using all traditional appearing bits.

 

Thanks for the responses fellas. I was thinking about it and I guess the main reason for not using a y-link would be the interference with the driveshaft. So what spacing are most of you guys using?