Question about suspension.

[Stallacrew]

I was looking at another thread and a fella was using some axles out of what looked to be an old Bronco/F-150 and it used those control arms which are super beefy.

This rose a question in me........

Why is the spring where it is (coil springs) instead of up closer to the frame....

This is my mspaint attempt to show what I mean.

Obviously you would need a high spring rate since there would be more leverage on the spring.




so those of you who know what you're talking about, let me know. It might be a HORRIBLE idea all together, but I just didnt know.

Where the black spring is obviously the stock spring location, and the red one would be new one. Of course the new spring would be on a perch that would be perpendicular to the frame.

 

[h2opete987]

your control arms (as well as all mounts) better have some serious beef to it. the way it is now, (nearly) all weight is transferred directly down the spring to the axle. with the spring part way down the arm (like the red spring) you get a large upward force at the spring/body point, as well as a HUGE downward force at the body end of the arm. after that, especially in a long arm setup, you have a large cantilever to the axle.

long-version-short, if done right, can it work? yes, but there are many chances to taco things as well

 

[JeepFreak21]

Why?

I could see if coil springs limited your wheel travel, but they don't really. I've seen it used w/ things that do, like coilovers, airbags, and shocks. I just don't think there's any need with coils.

Billy

 

[whitneyj]

not only that, but the ford radius arms aren't that strong, go to fullsizebronco.com for some carnage pics. of how those things fold like a wet noodle. granted a bronco is twice the weight. . .

 

[ehall]

take a piece of metal and hold it between outstretched hands. move one end up and down like it is the wheel. now put your knee in between.

same concept.

 

[XJ_ranger]

I love purposely loading links in bending!

 

[Weasel]

I love purposely loading links in bending!

but all the desert racers do it!

 

[XJ_ranger]

but all the desert racers do it!

They don't articulate, and they don't plan on getting rock rash on the links!

 

[Weasel]

oh phooey my sarcasm insert that I typed in at work didn't show up..

 

[xcm]

from doing research on rear 4 links, it puts A LOT more stress on the control arms,
for example, look at rock crawler 4-links, their lower links are only tube, now look a race trucks rear links, theyre MASSIVE! the differance is a lot of rock crawlers mount their coilovers/airshox to the axle, and desert racing 4links mount the coilover/shocks straight to the control arm (i know, apples and oranges, but it might still come into play)
mounting the springs/coilovers to the control arms would allow you to more wheel travel, 20" stroke shocks arent available!
i think the weight hanging over the wrong side of the spring would be a problem, and i think its gonna fold like a taco, unless its tig welded chromoly like the desert racers use. even then, im glad its you thinking about it and not me!


it also puts a lot more math into the mix when initially setting up springs.
its a fair question though, and i hope someone else with more suspension design experience would answer it completely, just for knowledge if nothing else!

also, i think the design your talking about is called a radius arm.

 

[xcm]

Why?

I've seen it used w/ things that do, like coilovers, airbags, and shocks. I just don't think there's any need with coils.

Billy

absolutely! this wouldnt be worth doing w/ regular coil springs, this is 2008!
coilovers or bust

 

[XJ_ranger]

i think the weight hanging over the wrong side of the spring would be a problem, and i think its gonna fold like a taco, unless its tig welded chromoly like the desert racers use. even then, im glad its you thinking about it and not me!

Definitely needs to be chromoly and TIG welded... MIG welds probably wouldnt work there...

you might be able to get away with aircraft aluminum, but ONLY if its TIG'd...

and has lots of holes in it - the holes actually add strength on desert cars - but for most rock crawlers, its just for looks.



:gee::gee:

 

[Jump This]

- the holes actually add strength on desert cars - but for most rock crawlers, its just for looks.



:gee::gee:

I take offence to that remark!

 

[tbburg]

..,you might be able to get away with aircraft aluminum, but ONLY if its TIG'd...

Minor correction:
"aircraft grade" aluminum wouldn't be aircraft grade any more if you weld on it, no matter what kind of welding it is. Aluminum(any alloy) doesn't temper or "harden" like cro-moly as it cools. After you weld it, it has to be re-heat-treated to regain it's strength. Start with a piece of 7075-T3 and weld on it. it is now 7075-T0(dead soft) along the weld lines. Thats why all aircraft grade aluminum assemblies are riveted or bolted together.

 

[XJ_ranger]

Minor correction:
...

My whole post is in need of a MAJOR correction, but thanks... :laugh3:

 

[Weasel]

Minor correction:
"aircraft grade" aluminum wouldn't be aircraft grade any more if you weld on it, no matter what kind of welding it is. Aluminum(any alloy) doesn't temper or "harden" like cro-moly as it cools. After you weld it, it has to be re-heat-treated to regain it's strength. Start with a piece of 7075-T3 and weld on it. it is now 7075-T0(dead soft) along the weld lines. Thats why all aircraft grade aluminum assemblies are riveted or bolted together.

Yeah Ranger, no welding aluminum on that baja car and calling it aircraft grade on your design report.

Wish I knew that earlier...:confused1