Making Control Arms (what is going to be stronger?)

[VAhasnoWAVES]

i plan to build my own 3 link while installing a HP44. plan to use heims all the way around (CAs, track bar, and steering). seems the standard is to use threaded inserts welded into DOM. but i just started working at a machine shop, and have a few options. one of which is directly tapping to accept heims...

concerning DOM, is a smaller diameter of XXX" wall stronger than a larger diameter of the same XXX" wall thickness? i would think a smaller overall diameter (direct tapped) of the same wall thickness would be stronger and resist bending better than a larger diameter piece with the same wall thickness and welded insert?

correct?




also, what about solid stock drilled and tapped for heims? is all solid stock created equal? is it stronger yet, than the alternatives?

 

[Vanimal]

iconcerning DOM, is a smaller diameter of XXX" wall stronger than a larger diameter of the same XXX" wall thickness? i would think a smaller overall diameter (direct tapped) of the same wall thickness would be stronger and resist bending better than a larger diameter piece with the same wall thickness and welded insert?

correct?

no, you are very far off. a 2" diameter .1875 wall tube is far stronger than a 1.5"dia .25" wall tube. probably like 40-50% stronger, without doing the math.

also, what about solid stock drilled and tapped for heims? is all solid stock created equal? is it stronger yet, than the alternatives?

bad idea, just stick with the tubes and threaded inserts

 

[DeftwillP]

I've been talking to ironman4x4fab about doing a 3-link using 1.75 .281 walled lowers direct tapped for 1.25 Johnny's. I can't imagine that it's not strong enough but I suppose strong enough is relative.

 

[VAhasnoWAVES]

him or dan at ruff stuff may be the guys to talk to.

what have they told you?

 

[Vanimal]

I've been talking to ironman4x4fab about doing a 3-link using 1.75 .281 walled lowers direct tapped for 1.25 Johnny's. I can't imagine that it's not strong enough but I suppose strong enough is relative.

that very well may be so, but i was refering to the fact that he thought that smaller diameter tubes were stronger, and the fact that he mentioned using solid bar stock.



FWIW, i severely bent one of my rubicon express arms my first time out with them.

 

[Rawbrown]

there is an excel based 3 link and 4 link calculator out there. the 4 link calculator very specifically has a link calculator function that can let you compare tube size and different types of tubes from cold rolled to titanium.
structurally as an example. I did the math for my internal cage. Most people were using 1.5 .120 wall tube. But I wanted to save weight so I went with 1.75 .095 wall tube. Which was structurally stronger and had a higher resistance to bending but it was also lighter. The only downside to .095 wall tube is that its abrasion resistance was not as good as the .120 wall tube. But in my case, most of my cage was internal. only in the areas like the boatside rails did I opt for .120 wall.
How does this translate to control arms? Same theories apply. for UCA's, you can run a lighter thinner tube, or smaller thicker tube. UCA's are not susceptible to bending in the middle unlike the LCA's. In theory also, The magic # for LCA's that is most critical is the resistance to bending. It needs to be able to IIRC take 1.5 times to weight of the jeep or front of the jeep or something like that.
All #'s that your able to calculate with the excel 4 link calculator. oh wait, its been a while. try this.
http://mysite.verizon.net/triaged/4linkcalcv15html/index.html
have fun.

 

[jeannies_driver]

7075 solid aluminum drilled and tapped to fit your heims. It will bend and return straight better than steel.

Why do you want heims over a johnny joint ? Heims will be very harsh on the ride.

Larger tube in the same or slightly less wall thickness is always strong than smaller tube.

Vanimal, If you bent RE's lower links than you bent .250 wall chromoly. Did you run it off a cliff ?

 

[Rawbrown]

My LCA's are solid, non adjustable. If you engineer it right, you don't need to adjust. I used RE superflex joints for my LCA's.

 

[Vanimal]

7075 solid aluminum drilled and tapped to fit your heims. It will bend and return straight better than steel.

Why do you want heims over a johnny joint ? Heims will be very harsh on the ride.

Larger tube in the same or slightly less wall thickness is always strong than smaller tube.

Vanimal, If you bent RE's lower links than you bent .250 wall chromoly. Did you run it off a cliff ?

7075 does have a higher yield strength, but if it bends, i would never use it again as it will work harden and fail. plus the threads won't be nearly as strong, so you'd have to use heims or JJ's with LOTS of threads. Which leaves Currie out.

They were radius arms. i tried climbing over a 4 or 5 foot rock, goosed it at the top to try to clear the control arm bracket since i kept getting hung up on that, and it put probably a 15 degree bend in the arm when i came down on it. it's not .25 wall chromoly, i can promise that.

 

[jeannies_driver]

Large johnny joints have 3 or 4" of thread. We use them along with 2.5"(?) 7075 links on a competition buggy and have yet to have an issue with the joint pulling out of the link itself. We've blown the joints into pieces and bent the housings on them but never had a thread failure. We've even bent the shank on the joint but no problems with the links.

Sorry, I was thinking you had RE's long arms which are chromo, not the short arms. I have no idea what they are made of.

 

[Vanimal]

Large johnny joints have 3 or 4" of thread. We use them along with 2.5"(?) 7075 links on a competition buggy and have yet to have an issue with the joint pulling out of the link itself. We've blown the joints into pieces and bent the housings on them but never had a thread failure. We've even bent the shank on the joint but no problems with the links.

Sorry, I was thinking you had RE's long arms which are chromo, not the short arms. I have no idea what they are made of.

interesting... i'm just paranoid about fine threads in aluminum.



they're 3 feet long.