Project Tech Snob

[kastein]

I like that trick for getting the tubing stubs out of the inner Cs. Never really thought of it because I always think "heating things makes them expand"... will have to remember that.

 

[EndlessMtnFab]

I normally am not a fan or proponent of the parts made & sold by Clayton's ... however, I have to admit these are the nicest coil spring mounts I've seen. I like the idea of no metal-to-metal contact offered by this setup. Definitely not cheap, but should keep squeeks and major clangs down. You can also see how I had to shorten and reshape the driver side of the truss to make room for a coil mount (and correct the twist in the truss body).


That shiny brass thing is my ARB port. I have tapped it from both directions so that I can use flared fittings instead of the supplied ferrules. Makes removal a cinch. :cheers:

Truss is welded on, as are the coil spring mounts. I have not fixed the track bar mount as this point.

Everyone knows how the factory UCA's mount to the axle. The bushing is pressed into the cradle and the arm sits around it. In my opinion, this isn't the best design. In particular, with the cast in mount (driver side) you are limited to one angle unless you choose to bent offset tabs or cope the tube differently. Bushing replacement is also a well documented aggravation.


As such, I decided to make my own design. The tab was made with additional holes to offer adjustable anti-dive properties (we will discuss this later in the thread). And I wanted to make sure I had the proper amount of vertical separation (again --- we address this later).


So ... we have tabs looking like this !

And, when welded up to the truss (with braces, of course) .... it looks like this

I am going to be using a LCA bushing in that bracket assembly rather than the smaller UCA bushing that is normally used. Take notice at the increased size of the bolts used for the UCA. 10mm is the factory size and is usually sufficient. For some folks, I will change to a different bushing that allows me to use a 12 mm bolt. But I went up to 9/16 for as much strength as I could. Such tabs could be made to utilize the smaller UCA bushings and you could revert to using TJ rear uppers (with joints) for even greater flex. And would probably be cheaper than the Currie UCA mount that is offered.

 

[dgrigorenko]

very nice work. keep it up, and thanks for sharing some awesome tech with everyone

 

[XJSnowMan23]

agreed^ this is a heck of a job

 

[CherBear]

This is darn nice build you have going! Keep up the work.

 

[Seiler]

I guess I won't have to wander over to Cherokee Forum to check it out. :looney:

Looks good.

Scott

 

[collkid]

Pretty sweet.

are you keeping the stock trans?

 

[EndlessMtnFab]

AX-15, yes.



Nothing going on there ... other than the need for a new bushing in the shift tower.




Joe

 

[BlueGerbil]

Looks great! Thanks for sharing!

Subscribed.

 

[JNickel101]

If I still lived back home in PA, I'd be tempted to drive up I-81 and check this build out - if you didn't mind of course - this is amazing....

 

[EndlessMtnFab]

Definitely wouldn't mind if you came over (or anyone else, for that matter).



I could use some volunteers to help me finish this POS. I've got a lot left to show everyone and a LOT left to finish up.



Maybe I should do a NAC tech day?




Joe

 

[wolfpackjeeper]

nice build, I wish I had the time for something like this right now.

 

[EndlessMtnFab]

Next up ..... Front Suspension !




This post will be focusing solely on the theory & concepts behind what I have chosen to do for my XJ. Everything here is being described in rudimentary terms just for simplicity sake. I am very aware that a good portion of the readers understand more advanced suspension design. Pictures will be added later, as I go along.



I have chosen to go with a "3 link" setup. For those that aren't up on terms, it simply refers to the number of control arms I have chosen to run. In this case, 2 lowers and 1 single upper. I will retain the track bar for axle locating. To be more precise, there are actually four links holding this suspension in place (the already mentioned 3 control arms, and 1 panhard/track bar).


The factory front suspension has a total of five links (4 arms & 1 panhard/track bar). The additional link will "over constrain" your suspension and has the potential to create binding at increasing levels of flex.


There are generally two types of accepted long arm setups. One is the commonly known "Y link" which is also known as a radius arm setup. The second is the popularly termed 3 / 4 link setup (one or two upper links, your choice). Although the radius arm setup is simple to design & build, I prefer the link setup for several reasons. Some of them include: Less stress on bushings/joints, pinion angle changes as you cycle, less chance of the axle dropping away under extreme droop, and a potentially smoother street ride.


As a quick side note ... some people will build a front suspension where the UCA will mount to the same point as the LCA (shared bolt & mount). In my opinion, this is still a radius arm setup of sorts. The stress is distributed out further (a very good thing) but the suspension movement characteristics more closely mimic that of a Y link setup.


There are many commercially available kits offered in both link & radius arm setups. But none of them really had all the features I wanted and did not have provisions for some of the goodies I have already installed (and ones I haven't installed yet). And so we go the custom route again.


Okay .... so where does this leave us? Beats me. :gag:

 

[EndlessMtnFab]

Now ... we have to set some parameters down.


First ... I did not want the arms/joints to end under the frame rails. That's a major ground clearance issue. The factory LCA brackets sit at 5 degrees ... which puts the arm squarely under the rails if you make an arm with an square cut (no additional mitering). A mitered/angled cut is an acceptable way to change your arm location. But how about new brackets? Going this route gives you freedom to change many things.


Second ... A baseline has to be established. Measure anything and everything you can on your suspension. Height from ground to LCA bolt (on axle & frame). Height from ground to UCA bolt (on axle and frame). Get those same measurements for your track bar. You'll need to get width measurements between the arms as well (at the frame and at the axle). The more information you have here ... the easier it will be to build a suspension that has similar characteristics to what you are used to (or perhaps want to change).


Third ... I need to be able to fit everything in one package. The doubler adds some extra DS length and changes the angles. And a D300 does not locate as far over to the driver side rail as a NP231 might. Lots of measuring & planning here.




We already know the doubler has already been in place for some time. Due to the extra weight and length ... some new crossmembers are needed. So it made sense to integrate the arm mounts to the crossmembers. That allows me to raise up the joints and tuck them out of harms way.



Bored, huh? Okay --- let's move to some fun technical terms and why we have to consider them. For the time being, I will only concern with terms related to the front suspension. For simplicity sake, I am going to give the definitions in lay man's terms. If anyone wants better or more technical definitions ... check Pirate4x4 or try google. irate1:


AntiDive .... The ability of your suspension to counteract nose dive during heavy braking.


Instant Center .... The imaginary point where the LCA and UCA meet way out in the distance (as viewed from the side). It can also be the imaginary point where angled upper or lower control arms meet in the distance (as viewed from above or below)


Roll Axis Angle .... How the body pitches/yaws/leans around the imaginary centerline of the chassis (Roll Oversteer/Understeer are related to this).


Roll Center ... Measured Height for where your chassis/body pivot laterally


Separation ..... The amount of distance between your UCA and LCA at either the body or frame. Will affect where your Instant Center meets and will affect your Roll Axis



Okay .... so what does this all mean? No clue !! I fell asleep half way through typing this. :speepin:

 

[EndlessMtnFab]

There are a few books that go into much greater detail how to calculate all those fancy terms I just posted. I'm not one for that kind of patience. Thankfully, Dan Barcroft from Pirate took the time to put all the necessary formulas into a very workable excel spreadsheet. Fellow tech junkies have helped to improve the calculator in terms of it's abilities as we push the envelope for designs.


Here is one of my preliminary designs of my front 3 link. The picture has already been resized once or twice. No squawking about how big it is. :moon:

This was probably one of maybe 5 different builds I tried. At this point ... I am trying to get workable numbers based on rough constraints (chassis height, crossmember location, track bar location, etc). Now you can see the usefullness of all those measurements taken before.


So what's wrong with this preliminary setup? Well .... a few things. The roll axis is " by text book standards " too high. I feel it should be closer to zero if not slightly negative. This will slow down how fast the chassis reacts around that imaginary pivot point. I'd also like to see the Anti Dive (labeled as Anti Squat in the picture) higher. And a slightly higher roll center will help keep the vehicle from wanting to flop.



But at least we have somewhere to start. Next is start laying it out and cutting !

 

[Menzenski]

Definitely wouldn't mind if you came over (or anyone else, for that matter).



I could use some volunteers to help me finish this POS. I've got a lot left to show everyone and a LOT left to finish up.

I'm only about three hours away. I'm no fabricator myself, but a good friend of mine is, and I've helped him build a hot rod and several choppers. If you need somebody to give you a hand, I'd love to come help out.

 

[EndlessMtnFab]

At any rate ... now that we have the fundamentals down *ahem* .... you folks ARE reading this, right? And not just looking at the pretty pics? :twak:


So we start with the crossmember. You already saw (earlier in the thread) the rusted metal mock crossmember. Here is a quick shot showing how it hangs below the rail.

As a quick reminder, I mentioned earlier that because of the NP203 clocking, I am forced to have a "less than flush" crossmbember & belly pan arrangement. With the gentle touch of a butcher, I ground about 3/8 of material off the both of the doubler case. A custom transmission mount will allow me to place the drivetrain at the height I needed.



The end result will be a crossmember that is no lower than the factory crossmember. Yet still protects the bottom of the doubler, in addition to being the mounting point for my suspension. Is it perfect? Hardly ... but it's all a compromise.



And this is the profile I am looking to attain

While the mock crossmember was in place, I wanted to get a feel for where the UCA mount would sit. I preferred to place it on the driver side because the floorpan afforded more clearance (even though there is a driveshaft & part of an exhaust running in the same area).


The picture below shows just how tight things fit. The short mount to your right would have been the ideal spot (room wise). However, there is not enough vertical separation or distance between the lower mounts and the upper mounts. If you go back to my "techie" post .... you will understand that the lower the vertical separation, the lower your anti dive will be (and your roll axis angle as well). The tall mount on the left obviously has to squeeze between the driveshaft and the transmission.

At any rate ..... new tubing was cut up and shaped to fit.

The pockets were angled and boxed in to fit the Ballistic joints. I tucked the joints as high as I could while keeping the geometry where I wanted. The joint sits roughly 2 inches higher than if I had mounted directly under the frame rail. I also ran the tabs/mounts lower so that even when flexed ... no part of the joint would stick out below the tabs or crossmember.

 

[DeftwillP]

Where do I send the check for my crossmember?

 

[buzzbombxj]

Great thread, looking forward to watching this whole thing come together.

Endless m_____n fab?

 

[FlexdXJ]

Great thread, looking forward to watching this whole thing come together.

Endless m_____n fab?

He's either doing a lot or its coming together really quick! This thing is gonna be SWEET though!