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Old 01-20-2019, 02:17 PM   #1 (permalink)
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In Design phase, 4-link question

I've been reading many posts on 4-Link design and what ends to use, lots of info out there, This may have already been ask somewhere, but I missed it if so.
I have never designed a 4-link before, I think from what I have found I can work out the lengths, separation angles, etc. my question is this, while keeping on a budget, I'm looking for link end recommendations for the following use:
This rig I'm designing is a V8 4 seater Crawl/Trail rig that will be street legal, I'm running D44 front 14B-FF rear. Double Triangulated 4-Link front and rear. Not interested in doing super aggressive or high speed rock bouncing, more or less just exploring mild trails, desert, forest, etc, maybe even overland style stuff.

I was thinking of using QA1 1-1/4" Rock End with a 5/8" thru bolt and a 2.625" Poly Bushing with 5/8" thru bolt at the other end that is welded to link end.

I was thinking of using a poly bushing at one end to keep the road noise and vibration down and reduce cost.

Thinking of using 2" DOM .250 wall on all links.

So, I'm looking for input?

Does this sound like reasonable configuration? and would you run bushings at axle end or frame end? for front and rear the same?

Thank you for any and all input!!!

Kevin
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Old 01-20-2019, 04:12 PM   #2 (permalink)
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I'm building basically the same thing, so while i'm no pro i'll pass along what my guidance was and what my thoughts.

Lower links, 1-1/4" joints and 1/4 wall 2" are plenty fine, but that is way overkill for the upper links. i'm running 1-3/4x1/8 wall for my uppers because, well that is what the rest of the cage is so i have a bunch. i'm also running a hodgepodge of smaller joints because the stress is different on the uppers. they don't see the direct abuse from sliding over rocks and such that the lowers do.

I wanted to go with bushings for the same reason you state, but changed my mind after taking apart some that had some years on them. the joint side came apart with no problem, the bushing on the uppers was no problem, but the bushings on the lowers had to all be torched out. annoying enough that it made me spend the extra for some cartridge joints.

putting the bushing at either the axle or the frame will be about the same, just pick one side and make them all that way. Others will chime in probably, saying they've had lots of success and no issues with bushings, but i'm happy to not have them.
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Old 01-20-2019, 08:01 PM   #3 (permalink)
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I'm building basically the same thing, so while i'm no pro i'll pass along what my guidance was and what my thoughts.....

Provience, so what sort of joints did you end up using? and do you have much noise/vibration transmitted thru them?

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Old 01-21-2019, 08:45 AM   #4 (permalink)
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Not sure how you are building a street legal rig with a double triangulated front suspension? I don't think it can be done.

2"x.25" wall is overkill for your uppers 1.75x1.20 wall is enough since they don't take any hits. I would base joints on your shock travel. Typically bushings are good for about 10" of travel then you get pretty good bind and wear. Metal cloaks joint will give you more misalignment but cost the same as a johnny joint.

If you are looking to save money and use bushings, the JK and JL factory bushings are a pretty good bushing and you can find take off control arms everywhere that you could repurpose the joints.

5/8" bolts just raise the costs an a good grade 8 9/16" is fine.
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Old 01-21-2019, 09:22 AM   #5 (permalink)
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Provience, so what sort of joints did you end up using? and do you have much noise/vibration transmitted thru them?
mostly Low Range Offroad Flex joints, weld on cartridge style for one end and thread in style for the other. huh, they just show their large size on the website now. but they have the smaller size currie joints in stock.

I've also got some ruff stuff heims that i'm using.

as far as noise, with proper grease and servicing, the joints won't be any louder than the coilovers or exhaust or sheet metal or engine or tires, so i'm not really worried about it. IF noise is a problem, then that is treated on the inside of the car with heavy sound deadner, carpet and trim instead of just thin aluminum.

this is about as close a picture as i can get from my build that show the different joints. i



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Not sure how you are building a street legal rig with a double triangulated front suspension? I don't think it can be done.
why not? in this crazy world of electronic steering and hydraulic steering there is no need for a mechanical link from the frame to the tie rod, so you don't "need" to run a panhard/3-link

https://www.law.cornell.edu/cfr/text/49/570.7

link to 49CFR concerning steering
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Old 01-21-2019, 01:19 PM   #6 (permalink)
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mostly Low Range Offroad Flex joints, weld on cartridge style for one end and thread in style for the other.
Thanks I had looked at those too, glad to hear the noise is manageable.

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Originally Posted by Provience View Post

why not? in this crazy world of electronic steering and hydraulic steering there is no need for a mechanical link from the frame to the tie rod, so you don't "need" to run a panhard/3-link

https://www.law.cornell.edu/cfr/text/49/570.7

link to 49CFR concerning steering
Thanks also for the reference, I will read up up this
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Old 01-21-2019, 01:53 PM   #7 (permalink)
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Not sure how you are building a street legal rig with a double triangulated front suspension? I don't think it can be done.

2"x.25" wall is overkill for your uppers 1.75x1.20 wall is enough since they don't take any hits. I would base joints on your shock travel. Typically bushings are good for about 10" of travel then you get pretty good bind and wear. Metal cloaks joint will give you more misalignment but cost the same as a johnny joint.

If you are looking to save money and use bushings, the JK and JL factory bushings are a pretty good bushing and you can find take off control arms everywhere that you could repurpose the joints.

5/8" bolts just raise the costs an a good grade 8 9/16" is fine.
Thanks Dirt Man, I haven't heard that having triangulated front was not able to be made street legal, do you know why that is? or what it is that makes it not legal?

Thanks again!!
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Old 01-21-2019, 02:20 PM   #8 (permalink)
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A quick search didn't turn up the actual law, but there has to be a mechanical connection between the steering wheel and the wheels. No purely hydraulic or electrical steering.

If you use a conventional steering box and drag link with a triangulated suspension, you will likely have bump steer. The axle needs to move in an arc that matches the motion of the drag link. Side steer may work better than cross steering, depending on the link geometry.
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Old 01-21-2019, 02:20 PM   #9 (permalink)
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Just to echo everyone else I use 2x.25 DOM for the lowers and 1.75x.120 DOM for the uppers. I run Barnes Enduro's for my lowers and Heim's for he uppers. I'm not really a fan of bushing but if I really wanted them for some reason I'd run these (https://www.barnes4wd.com/Forged-Chr...ds-_p_419.html) and (https://www.barnes4wd.com/Forged-Chr...ads_p_721.html)
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Old 01-21-2019, 02:24 PM   #10 (permalink)
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What are you building off of? Is it a full tube buggy from scratch? Going to run out of real estate real quick up front for a 4-link if youíre building off a licensed vehicle.
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Old 01-21-2019, 03:39 PM   #11 (permalink)
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Quote:
Originally Posted by Quick & Dirty View Post
A quick search didn't turn up the actual law, but there has to be a mechanical connection between the steering wheel and the wheels. No purely hydraulic or electrical steering.

If you use a conventional steering box and drag link with a triangulated suspension, you will likely have bump steer. The axle needs to move in an arc that matches the motion of the drag link. Side steer may work better than cross steering, depending on the link geometry.
that is what i have yet to find.

NHTSA specifies that you must make it so that there is passanger protection from the steering. i.e. collapsable steering shafts so that you don't get impailed.

49 CFR talks about joint slop and steering input slop.

unless there is a state specific thing, i am very interested in finding a federal requirement. there does not seem to be one.

edit: this article talks about the infiniti Q50 that uses "steer by wire" https://www.wired.com/2014/06/infini...steer-by-wire/ and is road legal
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Old 01-22-2019, 05:15 AM   #12 (permalink)
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I have read one state that has on the books for mechanical connections for steering. Most just have how much slop the steering can have. Not one state has no hydraulic steering laws that I have found.

Not sure if they have special rules but some big trucks and cranes ect use hydro steering on the street.
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Old 01-22-2019, 05:23 AM   #13 (permalink)
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What are you building off of? Is it a full tube buggy from scratch? Going to run out of real estate real quick up front for a 4-link if youíre building off a licensed vehicle.
Rally Sport, I am working on a full tube frame design, from scratch. To be honest, I have never built one of these, so I'm in a huge learning phase.

If not a 4-link for up front, what else would work good? would have some flex, be road worthy, and not drive terribly?
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Old 01-22-2019, 05:37 AM   #14 (permalink)
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Originally Posted by Quick & Dirty View Post
A quick search didn't turn up the actual law, but there has to be a mechanical connection between the steering wheel and the wheels. No purely hydraulic or electrical steering.

If you use a conventional steering box and drag link with a triangulated suspension, you will likely have bump steer. The axle needs to move in an arc that matches the motion of the drag link. Side steer may work better than cross steering, depending on the link geometry.
Q&D, I was going to use a conventional steering box for this project. Since I'm new to this, I guess I need to look into side steer. Would you have any references for laying out the 4-Link and making a conventional steering box work properly?

Like I said, I'm still in the design stages, so any suggestions are are very much welcomed.
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Old 01-22-2019, 07:17 AM   #15 (permalink)
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Q&D, I was going to use a conventional steering box for this project. Since I'm new to this, I guess I need to look into side steer. Would you have any references for laying out the 4-Link and making a conventional steering box work properly?

Like I said, I'm still in the design stages, so any suggestions are are very much welcomed.
to get rid of the bumpsteer you would have to make the drag link match a suspension link in length and angles.

the part of the code here that would make what you propose illegal is in the brakes section, you have to be able to do a hard brake application and remain traveling straight
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Old 01-22-2019, 07:24 AM   #16 (permalink)
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A quick search didn't turn up the actual law, but there has to be a mechanical connection between the steering wheel and the wheels. No purely hydraulic or electrical steering.

If you use a conventional steering box and drag link with a triangulated suspension, you will likely have bump steer. The axle needs to move in an arc that matches the motion of the drag link. Side steer may work better than cross steering, depending on the link geometry.
people have been trying to find that law for about 20 years, so far no one ever has.
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Old 01-22-2019, 07:56 AM   #17 (permalink)
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to get rid of the bumpsteer you would have to make the drag link match a suspension link in length and angles.

the part of the code here that would make what you propose illegal is in the brakes section, you have to be able to do a hard brake application and remain traveling straight
MJ,
So is it that 4-Links don't break straight in this situation? or that most don't have a hand brake?
I have converted my 14Bolt FF to Disk with a mechanical parking brake, wouldn't that take care of this issue?

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Old 01-22-2019, 08:22 AM   #18 (permalink)
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Make your links as long as you can if you want to run a bushing at one end to reduce/avoid binding.

Genright did a double triangulated front that ran a steering box. Used a crazy linkage to get away form the bump steer.



I'm building a front double triangulated 4 like in my JK. Will be full hydro and driven on the street. Not worried about a law nobody can find, besides everything else I've done is technically illegal too.

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Old 01-22-2019, 08:46 AM   #19 (permalink)
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A conventional box requires a pan hard or track bar other wise the body and frame will move independently when steering. A pan hard with double triangulated is likely to result in ripping off the bracket or nasty bump steer.

The double triangulated 4 link keeps the axle centered thru out the suspension travel where the pan hard will pull or push the axle side to side. Running both causes the pan hard to rotate the axle during articulation. It will cause one side of the axle to drop and the other side to rise. This in turn will turn your steering wheel due to the drag link.
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Old 01-22-2019, 08:52 AM   #20 (permalink)
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MJ,
So is it that 4-Links don't break strait in this situation? or that most don't have a hand brake?
I have converted my 14Bolt FF to Disk with a mechanical parking brake, wouldn't that take care of this issue?
the guy above posted the answer.
a crossover drag link travels in an arc, a double triangulated hold the dif centered throughout its travel
combine the two and you get a steering change during travel.

that is why everyone that runs a steering box will be directed to a three link with panhard, with the panhard and draglink same length and angles
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Old 01-22-2019, 08:53 AM   #21 (permalink)
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MJ,
So is it that 4-Links don't break strait in this situation? or that most don't have a hand brake?
I have converted my 14Bolt FF to Disk with a mechanical parking brake, wouldn't that take care of this issue?
When you brake hard your front suspension compresses (brake dive), the double triangulation keeps the axles centered under the frame. With the compression the drag link flattens out and forces the steering wheel to turn. AS this is happening the track bar is trying to push or pull one side of the axle putting more down pressure on one wheel while trying to lift the other creating uneven traction/braking.
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Old 01-22-2019, 03:17 PM   #22 (permalink)
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What it sounds like is I should re-consider the 4-link front and maybe go to a 3-Link with Panhard bar front and a Double Triangulated 4-Link for the rear? or switch the rear to 3-Link Also?

Looking further, it sounds like the 3-Link would solve the issue with bump steer using a standard gear box. That seem to address most of the issues talked about here?

Then the next question would be, on a 3-Link, what sort of link ends are people recommending? and tube diameters?

Thank you all again for your help

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Old 01-22-2019, 03:29 PM   #23 (permalink)
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people have been trying to find that law for about 20 years, so far no one ever has.
Seriously. Itís like a damn urban legend. Brakes are hydraulic.

If you live in a place where you donít have inspections and things of that nature I wouldnít worry about it at all.
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Old 01-22-2019, 04:56 PM   #24 (permalink)
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you can run the same links and ends as on a 4 link.
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Old 01-22-2019, 05:52 PM   #25 (permalink)
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Check out this site. Is Full Hydraulic Steering legal

Several people on this site have Street Legal Vehicles that have Full Hydraulic Steering.


YMMV.
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