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4 Link Materials... Your opinion wanted

juanblzer

juanblzer

1/2 ton status
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Location
Chandler, Arizona
I am shopping around for a shop to do my 4 link setup for the rear of my blazer:
www.randyellisdesign.com wants $2500 without coilovers
a shop in phoenix called 4wheelers Supply wants $2500 without coilovers
and a shop called www.rpmfab.com wants $1500 w/o coilovers

I am wondering what materials you guys recommend the links be made of. RPM says they use 1-3/4 .120 wall mild steel and gusset it. They say that its plenty strong. Is this material strong enough?

Also, my current 4 link front built by randy ellis has bushings on the frame side and rodends on the axle side. Should this be repeated? What size rod ends?

I want to do it right the first time around and I hiway drive my blazer on a regular basis so structural failure is not wanted or appreciated /forums/images/graemlins/frown.gif

Also:
Kings or Sway aways? I'm running kings and wanted to stay same brand but RPM says they have the hook up for swayaways.
 
You might call FST. They are an offshoot of Fly-N-Hi Offroad. Flynhi sucks but FST is a good fab shop.

I personally don't think links out of 1.75 .120 wall would do. That is standard roll bar tube. I am pretty sure Marv had bent alot heavier stuff then that in the rocks on his buggy. Rocks don't forgive.

There is also another Fab shop I saw Arizona Offroad Design but I don't know anything about them. They might do the work, but I don't know for sure.

Harley
 
I would at least double the wall thickness to 1.75x.250wall for the lower links. The upper links will be fine at 1.75x.120wall.
 
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You might call FST. They are an offshoot of Fly-N-Hi Offroad. Flynhi sucks but FST is a good fab shop.

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Actually, these are the only shops that I really want to deal with. The guys at RPM (i.e. Ian Lilejebald) said they can do the links out of whatever I want but 1-3/4 .120 wall is what they normally use. I can get him to upgrade. Some interesting ideas thanks.
 
It also depends on what he means by "gusseting". If' he's talking about the double bar arms like the Wagoneer guys run, where each arm is made from multiple tubes, bent up for clearance, and plated or gusseted along the length, with perhaps some extra skid surface under the bottom, then it might be fine. If he's talking about some straight tube with joints on the end, then no, I don't think that would be enough...

Also, if they normally build for Samis and Jeeps, their perception of “plenty strong” may not work for your cut down K5.
 
Exactly!
that's my concern...
I know randy knows his stuff... but $1000 is a lot of money and this shop is pretty new. They build comp. rock buggies and one of the main guys there (actually both of them) used to work under/for Randy Ellis when he was at 4wheelers supply's fab shop. I would guess that they learned from him but... I want to make an informed decision.
ANy particular questions I should ask? Particular concerns?
 
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I am wondering what materials you guys recommend the links be made of. RPM says they use 1-3/4 .120 wall mild steel and gusset it. They say that its plenty strong. Is this material strong enough?

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I was recently talking w/ a fellow wheeler and he said that he had not seen a lower link that couldn't be bent /forums/images/graemlins/crazy.gif.... I'm beginning to agree w/ him, as the ones I have (that I thought would be tuff enuf /forums/images/graemlins/ignore.gif) are all bent outta shape!... Of course, our discussion was limited to "straight tube" links and we weren't considering "reinforced" and "gussetted" links. So, I guess the lesson here is "Go BIG"! I'd think that .250 - .375 wall would be in order....

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Also, my current 4 link front built by randy ellis has bushings on the frame side and rodends on the axle side. Should this be repeated?

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This is a good practice to follow if you don't want to transmit alot of vibration and look to "slightly dampen" the forces to the frame. The drawback is that this design concentrates almost all the angular twist into one rod end joint... and w/ a flexible suspension the joints can be over-rotated. This is why I used rod ends at both ends of my links.

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What size rod ends?

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As big as you can afford to go!

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Kings or Sway aways?

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I really have no experience w/ either as I have yet to cough up the coin for Coilovers.... But I would think it better to standardize w/ your front in the event you wanna switch coils or spacers or anything..... just an idea. /forums/images/graemlins/tongue.gif

Have you thought about what link design you like? Triangulated uppers, lowers, or both....? How much +/- squat you like? ....

What about sway.... Do you currently run a front swaybar? Coilovers on both ends may find you dragging your doorhandles around a 30 mph turn... Frisbee and Watson have alot of experience here.... /forums/images/graemlins/ears.gif

I guess if it was me.... I'd have a design in mind, then see who has experience and practical examples of making it work...

Marv
 
You comment about over rotating the ends brings up another related question.

This issue would be completely resolved if someone could find a reasonably priced source for a (preferably sealed) twisting joint like Brook used on the Freak. Basically he uses bushings in both ends of his links and it works very well. He built his using a lathe and some B7 all thread so that the bushings would not be hurt by twisting the link during articulation, but I think that's not ideal for general use. It would be great is there were a bushed joint that could be put into a link that would allow 360* rotation. Sort of like leaving the jamb nuts off of a rod end so that it can rotate past the orb’s limits. Sure would save on big beefy high-misalignment joints.
 
do you mean a link that twisted on itself? Namely you hold one end of the joint and can spin the other end 360 degrees? I've been thinking about building something like that just for curiosity sake. I was thinking of using ball bearings though simple greased and bushed would suffice.
 
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What about sway.... Do you currently run a front swaybar? Coilovers on both ends may find you dragging your doorhandles around a 30 mph turn... Frisbee and Watson have alot of experience here....

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Do think about this. I currently am not running swaybars on my buggy but I have low unsprung weight compared to a chopped K5. Stephen did put a swaybar on the rear of his and has liked it alot. His is setup well enough that the sway bar only limited his travel on a test ramp by about 2 inches.
Every link that is on a vehicle can and will get bent. My rear lowers are 1 1/2" .250 wall sleeved with 1 3/4" .120. I bent one at easter this year. Both of Stephens rears are bent in a long gradual bed throughout their length.

My front lowers are 1 1/2" .375 wall and I have bent two of these.
I am trying to decide what to do different with the front lowers. I thought that I could drive different and get them to hold up but that hasn't worked either.
I don't think that anything more is needed for the rears as the one I bent took a big hit, and Stephen has gotten his to last with only a large bow to them mostly from sitting on rocks not hitting them.
Stay with the Kings
My .02 /forums/images/graemlins/thumb.gif
 
That leaving the jam nut off idea is what started a current design I have rolling around. Picture a large thread (like 1.25") rod. the rod slips inside of a link and screws in at a certain point. It has a torsion spring to allow it to have some sort of static centering ability. The threads are LH and RH to allow the links to lengthen and shorten as the suspension cycles in articulation but no change in length on flat compression. The length change keeps the axle perpendicular to the frame and takes away rear steer issues. I have yet to figure the amount of force it would take to actually build (probably not gonna happen due to large forces) but it is an idea I have been playing with.

As for the link material, think about what a .120 wall driveshaft can take (not much in a fullsize) that is what you links will be seeing on a regular basis. I say at least .250 for lowers on a full size.
 
I don't think that the rotating link idea is really all that neccasary. I have 16" travel coilovers on the rear of my buggy and use a Rod end on each end with moderate mis-alignment spacers and have not ever in all of the cycling that I have done come close to using all of the rod end travel.
I also think that the bushing Idea is good,on the frame end to take some of the harshness out of the links but you should be able to use some of the larger Johnny Joint type joints to get some mis-alignment out of that end. That should be all that is needed unless you want feet of travel out of your suspension.
 
The reason I like the twisting link idea is to avoid having to run misalignments, or even rod ends for that matter. With misalignments, you wind up with a smaller bolt, and to keep the bolt size constant, a larger end must be bought, which is still more money. If a bushing is used on one end, then the high misalignment is even more critical on the other end since you just removed most of the twist from the other end. Johnny/Jimmy joints are nice, but have their own high cost associated, and some do not have the misalignment capabilities of rod ends.

The easiest way to make a functional yet inexpensive link would be to use poly spring bushings on the end with the threaded rod in the link. That would support an essentially unlimited amount of misalignment along the axis, and a full 360 would only have the effect of just running out one thread longer. But I don't like the idea of leaving a jamb nut off a rod end or the stud in the link due to wear/slop issues. I suppose you could slip a piece of bicycle inner tube or something over it to seal it, but it just does not float my boat.

It would be sweet if we could come up with a budget link setup that used common (read inexpensive) parts to provide a tight, rotating link joint. Something sort of like the trailer hub mounts for spare tire carriers, but that could hold together under compression and tension. I think poly bushings have plenty of flex to deal with the forces and flex in any other plane without significant bind or damage, it's that twisting on articulation that is a problem. They’ve held up on “The Freak” rather well last heard.

Maybe I’ll just use the 1” B7 stud and some coupler nuts turned down to form inserts. I’ve got some 1.5 x 0.250 DOM and some 1.75 x 0.120 left over from my tie rod, so that would be a start. Add on some angle welded to the bottom to provide a skid surface and it should be fine for what I need. Better tenability, flex, and MUCH better than 4 sets of leafs in 2 years. The only thing I’m missing is a few spring bushings and the B7 studs. Well, that and the custom tank to make room for the bridge…
 
You've basically got a linear force system in the links. I think Acme thread is called for in that situation. Screw thread typically wants to bind up when used to transmit power, Acme was designed for power transmission.
Look at older IFS cars (like 50's era & Merc's) they use an Acme type thread for their inner pivot points. How about that? They were getting a little gain in Caster in the Bump part of the cycle way back then.
 
Actually, ACME thread was my first thought. But have you ever tried to find high grade ACME thread in 1" (or there about)? /forums/images/graemlins/crazy.gif Can't get it from our local fastener supplier.
 
Have you checked out Industrial Pipe and Steel ? I get their catalogs periodically, and I definitely recall seeing ACME-threaded stock for sale. Whether it's stout enough for this app is unknown to me though... /forums/images/graemlins/dunno.gif
 
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You've basically got a linear force system in the links. I think Acme thread is called for in that situation. Screw thread typically wants to bind up when used to transmit power, Acme was designed for power transmission.


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Acme (Power Screw) threads are designed to convert rotary motion of a nut to an axial force - Jacking.... Though links are assumed to be 2 force members, they withstand an alternating load - a frequent reversal of compression/tension. Any thread that doesn't bind has slop. That slop will only get worse as it wears/fatigues in this application. /forums/images/graemlins/shame.gif Then the worst thing will happen when you land on a rock... This threaded joint subjected to bending is loading it in the worst way....

Teraflex did this exact thing for TJ's in the 90's..... Their links were known for "clunking"....

Hope I don't seem to just have a bad attitude about a suggestion here.... just I've thought about this one for a long time.... and I've never been able to convince myself it'll work /forums/images/graemlins/dunno.gif.

Marv
 
can someone post up a pic so i can understand what you are talking abought ??? /forums/images/graemlins/whistling.gif /forums/images/graemlins/thinking.gif thanks /forums/images/graemlins/waytogo.gif

/forums/images/graemlins/bow.gif Sorry I read this section to increase my 4x4 brain /forums/images/graemlins/bow.gif
 
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