BROR K20 Buildup

[BRORSAM]

Well, this couldn't be put off forever.....

I mentioned the radius arm pivot setup on Michael Niebuhr's Quagmyr. Not terribly complicated to replicate, but I was afraid it would limit wheel travel (Quagmyr's front airbabs were limited to somewhere around 9 inches of wheel travel I'd guess, and I knew I wanted much more than that).

Started thinking of different ways to do the pivot, and where the actual placement of the pivot point should be in relation to the center of the axle tube. Did several sketches, went through lots of scrap paper, considered the pivot on top, in front, behind, and below the axle tube, and couldn't make myself comfortable with any of those scenarios.

So....if top, bottom, front, and rear are all rejected, where else is there to go? Pivot has to be at the center of the axle housing. First thought was a large uniball (like 80 mm bore, such as an RBC MB80). Price of that little gem would be an issue---plus I'd have to hack it in half to fit it around the axle tube---plus replacing it if it ever wore out would be a headache.

Then I ran across something similar to this in an industrial parts catalog:



Shape was close to what I needed. This particular unit is made of Nylatron, which isn't all that flexible, but something similar made from a urethane might be the ticket. Such a bushing could ride directly on the axle tube, would be relatively inexpensive (compared to a 80mm uniball, anyway) and fairly easy to replace. I could easily fabricate flanges to weld to the axlehousing to keep the bushing from walking back and forth on the axle tube. All I'd need then is some sort of 2 piece "clamshell" style housing welded to the radius arm to accept the bushing.

Yes....we have a plan.....

[dirtygoat]

What happened to the other thread???

[BRORSAM]

Originally Posted by dirtygoat

What happened to the other thread???

TwinTurbo496 started that thread, but his version started in the middle of the build. I discussed with him, and we decided to delete that thread. This thread will tell the story from the beginning, have more tech, and explain the choces that were made during the build and the reasoning behind those choices.

I'm sure everything we mentioned in the original thread will be covered here, most likely with more backstory for a better frame of reference.

Was there anything in particular from the original thread that you would like to see more information on? I'd like to keep this one focused on the progression of the build, but I wouldn't object to starting another thread to cover other topics if desired.

[dirtygoat]

Originally Posted by BRORSAM

TwinTurbo496 started that thread, but his version started in the middle of the build. I discussed with him, and we decided to delete that thread. This thread will tell the story from the beginning, have more tech, and explain the choces that were made during the build and the reasoning behind those choices.

I'm sure everything we mentioned in the original thread will be covered here, most likely with more backstory for a better frame of reference.

Was there anything in particular from the original thread that you would like to see more information on? I'd like to keep this one focused on the progression of the build, but I wouldn't object to starting another thread to cover other topics if desired.

Right on...

I saved the other thread to keep updated and it disapearred...

Carry on...

[geo in a K5]

Now this is getting interesting

[HEAVY METAL]

lookin forward to updates!

[BRORSAM]

No one will ever accuse me of being a professional machinist, but I'm still pleased with the way these came out. Between the band saw, the drill press, the lathe, and the milling machine, I got about 9 hours worth of exercise.







One of these halves will be welded to the radius arm, and the other caps off the bottom. I'll have some U-bolts custom bent to hold the whole sandwich together, with the urethane bushing inside.

At this point I'm thinking that making the urethane bushing shouldn't be too complicated. I'll just need to build some sort of mold, and pour the bushing from a urethane rubber casting resin. Details of that to come later, but at least for now we're on our way with the radius arms.

[BRORSAM]

Also visible in the first pic of post #32 is the mockup of the transfer case. What we have here is a Chevy NP205 (gutted to make the mockup easier) clocked upwards to keep the bottom of the case above the bottom of the framerails. That was another one of the primary objectives of this build (keeping things tucked up better in the chassis). Looks as though a completely flat skidplate should be possible at this point.

At this point I'm entertaining options for the transfer case shifters, and thinking how convenient it would be if the transfer case shifters ended up closer to the driver's seat. Might be a little clumsy with a mechanical linkage---maybe a pair of push / pull cables instead? Actually, I think I have pair of cables in the shop that just might fit the bill....

By the way, you may notice a theme here---lots of useful stuff "just lying around". I'm a bit of a packrat and junkman (admitting it is the first step, I'm told) and have been gathering stuff that I thought might be useful for years. Here's my chance to put some of it to some use.

[BRORSAM]

At this point, I figured I had a workable plan in mind for the radius arms, so I decided to turn my attention to shock absorbers. I want all the wheel travel I can get (within reason).

Note: "Within reason" in this case means no Knight Stalker or Racesource monster truck shocks....not yet, anyway.

Based on some measurements taken from the mockup, it looked as though a 2 1/2" body coilover (like a King, or Sway-A-Way, or ???) with a stroke in the 16 to 18 inch neighborhood might be made to fit. This is going to be my first experience with coilovers, and it's reasonable to expect that I'll make some mistakes and destroy some parts along the way.

I also expected that whatever brand of shock I chose, I'd inevitably find something I didn't quite like, and would probably be doing some modifications of my own.

With all that in mind, plus seeing some favorable reviews, I decided to give F-O-A shocks a try. I won't bore anyone with pictures or details---F-O-A has their own website and covers all that quite well. Price also is quite manageable, and I probably won't feel too bad if I pretzel one while working my way through the learning curve.

The "bigger is better" voices wouldn't leave me alone, so I ordered a pair of the 2 1/2" body 18" stroke remote reservoir coilovers.

Didn't buy any springs yet---they will be my last purchase before the truck is up and running. I'll need a truly accurate reading of the weight on each corner with everything else on the truck complete before I'm ready to make a decision on spring rates.

[MNtal]

Keep telling the story,

And don't forget to mention the tech about the 14b front, especially what we discussed in the other thread, and hopefully these jackholes will keep their mouth's shut...

[BRORSAM]

Originally Posted by MNtal

Keep telling the story,

And don't forget to mention the tech about the 14b front, especially what we discussed in the other thread, and hopefully these jackholes will keep their mouth's shut...

Not to worry, it's coming. As the story unfolds, that won't be the last major change brought on by one of my "minor technical oversights". I just don't want to ruin a good story by jumping around or jumping ahead too much. After all, that's why we deleted the first thread.

[BRORSAM]

With the plan for the front suspension pretty much figured out (at least in my head, anyway), it was time to start thinking about the rear suspension. The plan here is to transfer the rear suspension from the previous version onto the new chassis. It's a 4 link design that I'd been running for years with little trouble (until the frame gave way).

Here's a reminder of the carnage from post 6:



Clearly, the 4 link bar attachment points at the frame need to be beefier than the bolt-on bracket in the picture. Here's where the shape of that crew cab frame starts working to my advantage. The crew cab frame has a long straight section that extends back beyond the rear wall of the cab, so the lower 4 link bars will tie directly into the framerail rather than several inches underneath.

Overall view:



Detail of attachment points:



Rear view:



Yes, the plan includes boxing the frame in the mount area, so nobody get worried about the mounting points just being in single shear. That will change soon enough.

[frikenwoodro]

Tie rod ends? Never seen that before lol

[BRORSAM]

Originally Posted by frikenwoodro

Tie rod ends? Never seen that before lol

BIG tie rod ends. Yeah, I'm sure somebody out there is going to disapprove of them simply because they're in single shear, but this very same set has been on the truck since 1995. Haven't broken, bent, or worn out a single one. And they did spend a significant portion of that time on the front (way back when the front was 4-linked). They lived when they were in front, they lived in the back---it's debateable which end of the truck is the tougher application, but it's worked successfully on both ends. Heck---just look at what they did to the poor 1/2 ton frame.

If you think about it, it's not that unusual though. Lots of over-the-road trucks use basically the same setup for the joints on their rear axle torque rods (albeit bigger). Matter of fact, I believe the old CUCV (2 1/2 ton GMC 6x6's) used that setup too.

Internally, these are nothing like the typical el-cheapo discount auto parts tie rod ends. The ball is a full sphere, wheras the cheaper ones use a half-sphere. The ball is encapsulated in a 2 piece high density plastic race, and there's preload built into the assembly to be sure everything stays tight. On top of that, they're greasable and sealed, which (for me) makes them preferable to ordinary rod ends.

[dirtygoat]

I dig the strange and unusual as long as it works...

Any part numbers or a source for the TREs???

[BRORSAM]

Originally Posted by dirtygoat

I dig the strange and unusual as long as it works...

Any part numbers or a source for the TREs???

I'll have to look around and see if I can dig up the part number. Nothing stamped on the part itself. Let me check around...

[BRORSAM]

Sorry if I confused anyone, I should probably have mentioned this earlier.

Anyone who has seen the original thread before it was deleted knows that the build has progressed well beyond what I'm showing here. (But even those pictures were at least a month old or so by the time they were posted.) As I mentioned in an earlier post, the intent here is to tell the whole story from the beginning, not start off in the middle of the build.

The reason I feel I need to mention that is that parts of the story are about to be told that don't seem to make a lot of sense---until you consider that at the time I was doing the work, some information I was lacking then is common knowledge today.

I'll try to make mention of those moments as the story unfolds. Again, sorry if that throws anyone. Oh...that also means that in real time, the build is taking much longer than it would appear just by looking at the dates of the posts...

[DieselS10]

I've gotta sign on for this one. I love it when people think outside the box!

[Y5mgisi]

Pretty impressive! I kinda like it!

[BRORSAM]

Originally Posted by DieselS10

I've gotta sign on for this one. I love it when people think outside the box!

Outside the box??? Dude---I've seen pictures of your truck. Looks to me as though you've got it covered. I'm really impressed with your suspension setup---I suspect more than just a few minutes of thought went into that one.

Anyway, I do appreciate the thoughts.

[BRORSAM]

Got the 18" coilovers in, and discovered a few areas of concern (for me):

Something didn't seem quite right about one of the billet lower eyes, so I pulled it apart for a better look.

View from one side:


View from opposite side:


My photography skills (or lack therof) aren't helping much to make my case here, but if you look very closely at the pictures, you would notice that the snapring grooves are not centered in the eye. The groove in the first pic is closer to the outer edge of the eye than in the second pic.

Beyond that, the spherical bearing seemed a bit loose in the bore. Not sure if that's a problem or not, I just expected it would be a tighter fit.


Much easier to see is this problem:



That raised "fin" on that crimp fitting is trouble just waiting to happen. Not sure whether others have seen something similar with their shocks, but I'll never trust a crimp that looks like this.

Aside from that, one of the shock shafts had a ding about midway up the shaft, and one of the shock reservoir tubes was dented on the end. I contacted F-O-A, and to their credit, they did provide a replacement shock shaft and reservoir tube.

I also mentioned the poor crimp on the reservoir hose at the time. I didn't make too big a deal of it at the time because I figured I'd be building my own reservoir hoses eventually (longer, and with proper crimps) so I could mount my reservoirs exactly where I wanted them.

I didn't bother mentioning the issue with the lower shock eye. The wheels were already turning to address that issue my way.

[BRORSAM]

I think I'd mentioned earlier that this is my first experience with coilovers. That said, I don't know if some of the things I'm seeing are typical of all brands or just the F-O-A's.

My understanding is that it is customary to use a lower spring with a free length equal to the stroke of the shock. So, in my case, these are 18" stroke shocks, and will therefore use a 18" lower spring.

Extend the shock fully, measure 18" up from the lower spring seat, and the coil separator falls here:



Now, the endcap on the shock body is a slightly smaller diameter than the body itself....so at full extension the coil spacer isn't fully piloted by the shock body, and recieves only marginal piloting from the body endcap.

I also don't know what I should expect from the springs, whether I can expect them to "take a set" and sag (shortening the free length) over time. I'm sure bad things would happen if that coil separator were to ever walk all the way off of the shock body, so I expect I'll be doing some sort of modification to ensure that can't happen.

I'm thinking I may fabricate a 3/4" long stop tube to be installed inside the shock body to limit extension of the shock. Doing that should make the position of the coil spacer at full extension look something more like this:



See the difference? Now, the full length of the coil separator is piloted by the shock body itself, and not depending on that (slightly smaller OD) body endcap.

I don't think I'm going to lose one bit of sleep over the little bit of travel I'm going to be giving up. If anything, it technically should make the shock rod less prone to buckling, as the column length becomes shorter, and the guiding of the rod at the body end is improved.

[BRORSAM]

Originally Posted by dirtygoat

I dig the strange and unusual as long as it works...

Any part numbers or a source for the TREs???

I was able to dig this up:

Left Hand: TRW L24SV8002K15
Right Hand: TRW L24SV8003L12


These are some older part numbers, and I wasn't able to find them on TRW's website. Looks as though TRW has a newer design that they're advertizing (the "DL Series")---allegedly a stronger, more compact, more cost effective design.

It's entirely possible that a good heavy duty truck parts shop would be able to find those parts or cross them to a similar offering in another brand. I was fortunate enough to purchase mine years ago from my employer. They were in production at the time on one of our product lines, but have since given way to a different design altogether.

[BRORSAM]

Things I didn't quite like about that F-O-A lower eye:

I wasn't impressed with the machining of the snapring grooves (not centered).
The bore for the spherical bushing seemed to be on the loose side.
The snap rings didn't seem to fit all that well.
The misalignment spacers didn't seem too cleanly made.
When it's all said and done, I'm still stuck with a puny 1/2" bolt.

On top of all that, it was starting to look like my front suspension design was going to come close to using up all the angularity available in the F-O-A lower eye. Rather than use the F-O-A pieces and hope for the best, I decided to look into alternatives.


First thought in my mind was to replace the F-O-A lower eye with a 7/8" heim joint with female shank. I'd then be able to use much beefier misalignment spacers and still fit a larger bolt. Unfortunately, 7/8" female heims are both uncommon and expensive.

On the other hand, heims with 7/8" male shanks are fairly common, and relatively inexpensive. So, a few minutes of internet shopping, plus some time on the lathe, and we end up with this:



The heim shown here has a 7/8" male shank and a 3/4" hole through the ball. The misalignment spacers shown allow more angularity than the F-O-A pieces, while still allowing a 5/8" bolt to pass, and the aluminum collar connects the heim to the end of the F-O-A shaft.

Yes, that means I'll eventually be trying to put a bigger mounting bolt in the top of the F-O-A shock as well, but that comes later.

[BRORSAM]

Not sure I've done the best job possible of describing what I have in mind for the radius arm pivot at the axle, and it may not be clear from just looking at the individual parts. Here's a snapshot of a CAD file that shows how I envision it all going together:



Next major task in the front suspension will be building a bushing similar to what's shown in post 26, but from a more flexible material---like a hard rubber or urethane. What could possibly go wrong?