Triangulated 4 link

[Longstep70]

Im doing this on a 59 Apache, not a 67-72 C10 so the frame is straight and i think its narrower.
I dont want to have too much hanging below the frame because I want to lay pretty much all the way out at full dump. Im setting these renders up at a 5" ride height and so if i setup the lower bar under the frame it has to be able to articulate upwards enough to accomodate the 5" drop and not interfere with the frame; that's why I have been trying to tuck them into the notch front.
I asked about the thickness of your lower bars becasue you recommended making them beefier than the uppers but yours look thinner. I notice the angle of your articulation points is different than the shots of the satchell on the Jag up at the top here. What's the reason there?

[Twisted Minis]

The uppers on that truck are 1.75" OD because the bags are on those bars, so they support the weight of the truck. If the bags where on the axle, I probably would have run a 1" or 1.25" .120 wall link bar. It's going to be different for every application.

I'm not quite following you on the last sentence. Do you mean the way the bushings are angled?




I've been building links that way for a while. I think it looks cleaner, and when there are bushings on each side there is less wear on the bushings, especially during articulation. Also when I thread the rod ends in and out to adjust the pinion angle, it only adjusts the pinion angle. If they where at an angle, they would try to get wide at the axle, and either shift the axle, or change the angle of the link bar and add some stress/misalignment to the bushing on the front. If there where rod ends on both sides then the misalignment would be a non-issue. But I try to use bushings on one side of a link bar at all times on a street driven vehicle. And I can also squeeze a little bit more triangulation out of the bar, because I can push the bushing just a little bit closer to what is next to it. Like on this truck, I was able to change the angle of the bar from 34 degrees to 38 degrees by changing the orientation of the bushing from perpendicular to the link bar to parallel with the axle tube. Mostly though it's a style I picked up, that I stick with, because I like it, and it is recognized as my style. No one else out here (in my area) does it.

As far as link clearance goes, I am not sure what to tell you without seeing it. And even just seeing pictures, my ideas still may not work. Maybe you should consider a backhalf, or a creatively shaped notch, or a different link setup. I am kind of partial to parallel 3 and 4 links with a panhard bar. They are just about infinitely tunable, and very simple to build.

[Longstep70]

Oh I've been thinking about a parallel 4 as a simpler alternative this last few days, dont you worry .....lol
Your pictures answered my slightly unclear question about the pivots being parallel to the axle rather than the bar. Does this affect the articulation in any significant way? I can totally see how it would make your adjustments much easier, especailly with regard to the width at the axle. They do look clean too.
My images are a little rough but they are to scale. One grid square per inch. I played around with the bar lengths and the notch position and then ran the numbers through the 4-link analyser i found at Pirate 4x4 http://mysite.verizon.net/triaged/4l...tml/index.html
and I think I got some pretty decent numbers although I have no idea how they change under articulation. the performance trends analyzer demo version doesnt let you do anything useful so I cant see how things change as the axle moves.

These numbers are with 16" and 20" bars for the 80% upper to lower relationship and with the lower bars tucked in the front of the notch and the pinion back to the factory offset.
The driveshaft loop is wider and offset to match. The lower bar just tucks inside the notch:

Is the side offset on the pinion in addition to a front-to-back rotation on the housing or are these installed with the pumpkin face perpendicular to the ground instead of tilted up a couple degrees? From those pics of the jag with the satchell it looks like he centered his driveshaft and the pumpkin is offset to compensate. Its hard to be sure.
Maybe a parallel 4 and panhard is just the easier way out here. I was hoping for something a little different without getting too complicated and I liked the idea of no panhard or watts. I'm already in the realm of a custom notch and bars here with this design though.
I am planning a trip to the Pleasanton goodguys at the weekend to do some research and maybe there'll be something there that helps me decide.

[Twisted Minis]

The bars seem to be getting a little bit short, if you are planning on a 5" ride height. That sounds like you plan on 10 inches of total travel, which means your wheelbase will change a bit with bars that short.

What if you built a really beefy bar with a light bend in it to clear the notch? You could get just as much triangulation and a bit more length.

[Longstep70]

I'm not sure how I'd go about doing that ; it might be beyond my capabilities.
Getting the lower bars much longer is tricky with the 45 degrees of triangulation and that offset on the driveshaft hoop unless I drop them way down below the frame. Having said that, even without worrying about the notch the absolute longest I can get with the bars right out by the wheel and the centers clear of the driveshaft is 24" long on the bottom. i dont know if that's long enough or not.
Maybe that parallel 4 is the wiser choice after all? I just want something with a decent ride and predictable handling; Im not building a race car but on the other hand i dont want to throw so mething together.

-Andy

[PBFAB.COM]

Originally Posted by Longstep70

I'm not sure how I'd go about doing that ; it might be beyond my capabilities.
Getting the lower bars much longer is tricky with the 45 degrees of triangulation and that offset on the driveshaft hoop unless I drop them way down below the frame. Having said that, even without worrying about the notch the absolute longest I can get with the bars right out by the wheel and the centers clear of the driveshaft is 24" long on the bottom. i dont know if that's long enough or not.
Maybe that parallel 4 is the wiser choice after all? I just want something with a decent ride and predictable handling; Im not building a race car but on the other hand i dont want to throw so mething together.

-Andy

Is the notch built already?

If not why not look into a slightly different notch design? As Twisted mentioned, it can be much easier to design the notch and or back-half to accomodate the link set-up one intends to use.

[Longstep70]

No the notch isnt built yet so it *is* the place where i can make room to accomodate the bars. I'd been kind of planning to buy a notch kit with the parts pre-fabbed but I think if I go this route Ill have to make my own. It will need to be deeper longitudinally and probably the front leg will have to be less vertical to open up that front corner a bit. I modelled it out in 3d and it was only a couple inches longer at the top of the bridge and a few degrees agled further forward at the front corner.
Once again I come up against my limited fabrication toolset though for making up the notch pieces and bars, which is why i was originally looking at kits.
Is the 24" link length I mentioned above long enough do you think? Even with a custom notch thats about as long as I can go with the 45 degree triangulation.
here are the numbers from the suspension calculator with the longer bars. Are they ok?


-Andy

[Twisted Minis]

24 inches would be plenty long if you can make it work. I would probably go with a 20~21" upper bar at that point.

I'm sure Nate or I could build you a custom notch if you don't feel like you're up to it. I think building the frame around the link setup, and not vice verse, is the best way to go.

[14U2NV]

Longstep70,

I think you are using an older version of the 4 link calculator. I noticed you mentioned not being able to see pinion angle change through travel. This is the link to the new calculator from the same guy and it has pinion angle change built in. It also plots the suspension for you in a graphical way.

4 Link Calculator

BTW it's a download and you have to have Excel to run it.

Chad

[Longstep70]

Thanks Chad, I'll give that a try.
Can anyone say whether those numbers I have posted are good or not because if they are I'll go ahead and work up a new render of the bars in place and the new notch dimensions. Is that Roll center too low? its right at the bottom of the pumpkin at ride height. Anti squat % seems to be an issue where I've seen disagreement as to whether its good to be near 100% or not.
As it stands I have the lower bars 5" below the bottom of the axle housing so that bracket is qoing to be quite long isnt it? If I tuck the bars up a little higher and shorten the mounting bracket I lose a little AS and bring the RCH up about an inch.
Twisted (sorry I don't know your real name..) I might just take you up that offer when I am settled on the design since I am within driving distance of you so I could presumably place my order then drive up to collect?

-Andy

[Twisted Minis]

My name is Seth, and yes you could pick it up from me.

I like setting the roll center up around the bottom of the pumpkin. I am doing a 3-link on an S10, and that is about where I will place the roll center height. As far as Antisquat, everyone seems to have their own preference as to what they like. And it depends on the type of driving you want to do also.

[Longstep70]

Thanks Seth. Reading around a little more it seems for a street vehicle I should shooting for 50-55% AS.
Using the Excel version of the suspension calculator that Chad linked (thanks Chad) I have started tweaking but right now I have a RCH of 12" which is just above the bottom of the pumkin and below the pinion snout.
I can get it lower but to do so I have to drop the lower bars and I start to worry about how long the mounting tabs on the bottom of the housing are. Is 4-5" too long?
BTW the dynamic #s in the Excel calculator show the pinion angle changing by about 0.3 degrees per inch of bump so at the full 5" dump there will only be 1.4 degrees of change.
-Andy
Edit - one other thing: how much change in the RCH and AS numbers should I be aiming for?

[Longstep70]

So my research trip to Goodguys threw up very little but I did see a bunch of 4 links that seemed to be set up with weird geometry. Parallel 4's with no panhard and a tri-4 that must have had its IC way high and back behind the rear end.
I could stay simple and go for the parallel 4 but its seems a little boring....
-Andy

[spankbomb]

Very informative thread. Any updates?

[Longstep70]

Sorry i haven't been on here much lately - I started a new job and my parts runner 68 C10 has been off the road so Ive been trying to get that rolling again and haven't had much time for this. I have a wiring/electrical problem and i don't even know where to begin tracking it down.
I did tweak my 3d model some more and got the numbers a little better but since i never got any feedback on how good this last lot were I figured the thread was done and never posted them. I'm hoping to get back to this in the near future. I'll post pics when I do, if you like.
-Andy

[Ghostwhite]

I love this thread.....

Originally Posted by Longstep70

Is the side offset on the pinion in addition to a front-to-back rotation on the housing or are these installed with the pumpkin face perpendicular to the ground instead of tilted up a couple degrees? From those pics of the jag with the satchell it looks like he centered his driveshaft and the pumpkin is offset to compensate. Its hard to be sure.

I am wondering if anyone can answer this previous question.

Thanks, Ghost

[LONGHAIR]

I'm pretty sure I read that this was just a working drawing, and that the housing was going to be shortened before the final install. Then he will shorten more on one side to compensate.

[Ghostwhite]

It almost sounds like the offset differential may be kind of a substitute for 3* of pinion angle correction in order to keep the u-joints loaded. I am a newbie to drive line geometry.

[LONGHAIR]

I agree completely, but some people just can't deal with things being "off-center". As long as there is some angularity somewhere, it doesn't really matter where.

[fiddy9apache]

heres mine, this might or might not help. my loweres are striaght and are onr the out side of the frame.

[LONGHAIR]

The dreaded red X

[fiddy9apache]

hmmm thats odd, its a [img] code from photobucket.

[Longstep70]

Originally Posted by Ghostwhite

It almost sounds like the offset differential may be kind of a substitute for 3* of pinion angle correction in order to keep the u-joints loaded. I am a newbie to drive line geometry.

I have not been around here for a while... so I was surprised to see this thread anywhere near the top. I'm hoping to get back to this deal very soon.
I don't have an answer to your question but your quote above is pretty much my assumption. If anyone knows for sure I'd love to know one way or the other. I'd been keen to center the pumpkin to help with the arm attachment.
I notice last time i posted on here my 68 had an electrical problem i couldn't figure out - i can't remember what that was but i fixed and guess what? Right now it has another electrical problem I can't figure out and it's taking my time away from the "59.
Some things never change...

-Andy

[Ghostwhite]

I love reading all these old threads!(I'm currently browsing around page 150 of the suspensions category)

Very informative. I would rather bump this thread with an additional question and give someone else the chance to read this very informative thread than start a new one.

[slimneverdies]

Ok Im reading this and still trying to decipher a few things. Does it matter which of the bars (either upper or lower) is parallel to the ground at ride height? Also do I set the pinion angle at 0* or the opposing angle of the trans output? I know I have to setup everything inside the frame but the pics are just a mockup