It's An OCD Thing, You Wouldn't Understand

[inVERt'D]

Yeah, a double cardan at each end of that section of shaft. It allows you to wrap the driveshaft into multiple compound angles without vibrations. Look up LP magazine driveshaftology. They have a good example on an offset diff being fed from a Dana 20.

I'll look into it. I have a couple I could probably use.

Worth on the street is that two piece driveshafts on the front suffer from reliability problems.

If that's the case, there's a reason for it, and possibly a good solution too.

[inVERt'D]

Another thing I had to work out was the shape of the LCA tabs. Below is an unfinished version 1 drawing. It was designed for to get some decent ground clearance, and hopefully not too much anti-dive geometry (the front counterpart of anti-squat). The larger circle is the outside diameter of a ballistic joint ~3”. This design doesn't protect the joint very well. I drew some different versions of this that protected the joints better, gave better anti-dive (AD) numbers, etc., but I'll spare you. Note that the bottom of the crossmember tubing is flush with the bottom of the frame.


After doing some more research and playing with the 3-link calculator some more, I realized that the best AD numbers (according to prevailing thought) would require me to place the brackets where they would hang up on the rocks. I screwed around with a design that would allow me to raise and lower the entire crossmember, but decided it wasn't worth it. I decided to go with the best AD numbers. Since the crossmember is removable, I could make a high-clearance version later and compare the performance. I'd rather start with better performance and know what I'd given up for better clearance. That would be educational.

As a side-note, another way to improve AD geometry would have been to move the brackets back quite a bit further, but I don't like the options that leaves me with for a crossmember.

Below is the v.2 link tab, which is used on the v.1 crossmember. The v.2 crossmember will probably mount the link ends somewhere in the neighborhood of the v.1 tab's positions.


Comparison of versions 1 & 2

[inVERt'D]

Scrap Metal Art

Floor board for an old fork lift is some great 1/4” scrap.



Some of the nicer scrap metal around here. Left over scraps from a bridge project or something, and the anti-rust paint/primer really works. 1/2" high-quality mild steel = medium-duty tabs. I can't make the rocks duck, but maybe I can make some of them wish they did. Also in view is the 2x2, .250" tubing that will form the core of the crossmember.


Saw a bit of rusty steel in the dirt, kicked it, and up popped some 1/4" plate. Lucky day! It's good to be a redneck.

[inVERt'D]

Scrap metal art/ Front LCA Crossmember (cont.)

Made the basic frame bracketry first, since it would help with checking fitment. Did I already say it's going to be tight in there?


Cut some notches out for the body mount brackets. This is just the rough shape I used for early mockups. They will be more streamlined and the square access holes will be cut into the bottoms.



They go kinda like this. I think I moved the vertical part to the middle after these were taken. There will be fully tied to the frame rails before it's all over.


Drilling holes in tabs. LCA tabs on the left, and v.1 frame-side brackets on the right. At this point I was still entertaining the idea of making the crossmember height adjustable. If I stayed on that course, I would have eventually made 5-hole laminates to go over these. Instead of (5) 1/2” bolt holes, the brackets will have (2) 5/8” bolt holes. Like I said earlier, I decided the adjustability wasn't worthwhile. There just isn't enough room to go higher, and going lower means worse ground clearance. I decided I could later make a higher-clearance crossmember for rock crawling.


My first idea on how to configure the tabs. Ended up changing the tabs a little, and their configuration too. The ones with the thick vertical parts were moved to the outboard and aft sides of the crossmember. I'm just showing you this stuff to cornfuse you.


Some of you may hate this. Not a great pic, but here's a shot that shows an early mock-up. The crossmember is just resting on the bracket, and will be 1/4” lower as per the drawings. The fore-to-aft position is a close approximation. I plan to make ramps for the rears of the tabs to make them more slippery when backing up.


More on its way...

[aw12345]

David, here is a constructive observation. Since you are plenty creative, lob the front of the frame of in front of your lower control arm mounts will give you better triangulation for the lower arms, lots more room for your creations and just tube the front end. Will make a lot of things in the front easier, including a nice front end stretch. Why limit yourself to the constraints of the frame in the front. Same goes for the control arm mounts, move them to the outside of the frame and you can run a one piece driveshaft. Which will make you a lot happier in the long run. Lot of people have reliability problems with 2 piece front driveshafts. It works fine for crawling, but for hi speed driving it isn't the best solution unless you have select able hubs. Not criticizing, just trying to help you along to the path of the dark side my Swiss cheese brother

[inVERt'D]

David, here is a constructive observation. Since you are plenty creative, lob the front of the frame of in front of your lower control arm mounts will give you better triangulation for the lower arms, lots more room for your creations and just tube the front end. Will make a lot of things in the front easier, including a nice front end stretch. Why limit yourself to the constraints of the frame in the front. Same goes for the control arm mounts, move them to the outside of the frame and you can run a one piece driveshaft. Which will make you a lot happier in the long run. Lot of people have reliability problems with 2 piece front driveshafts. It works fine for crawling, but for hi speed driving it isn't the best solution unless you have select able hubs. Not criticizing, just trying to help you along to the path of the dark side my Swiss cheese brother

Happy to have the constructive observation or criticism, Art!

First, I intend to do a "front-half" eventually, but as silly as it may sound, I can't afford it now. Maybe I'll find my way into a set of coilovers by then and make my life simpler. Second, as far as the crossmember goes, it's part of my overall plan to use this Jeep as an experimental platform for suspension geometry. It gives me more freedom to place and move links than I could ever get by simply attaching them to the frame rails. Except, of course, that I can't place them as far outboard as the frame rails, but doing so creates roll-oversteer geometry, and I don't see any benefit in that at all.

The front driveline was what concerned me most, but in short, I believe I can solve any issues pertaining to it. I don't have any first-hand experience with two-piece front drivelines, but I did do some research before committing to one, and I've done more since. From what I've been able to gather (i.e., the following is not the gospel), the problems are generally due to a number of factors, including, but not limited to:

Alignment/ vibration problems:
1) The overall driveline angle putting the first (t-case side) shaft at an upward angle so screwing up the vertical alignment.
2) Using a two-piece driveline to go around an engine and/ or transmission, and so creating significant lateral misalignment.
3) Using a single pillow-block style carrier-bearing/ slip yoke setup with in any setup where there is misalignment in the first shaft. The proper setup for this type of carrier bearing should have as close to 0* misalignment as possible.
4) Misalignment problems in the second (pinion-side) shaft which may or may not be related to the above issues.

For a long time, the standard way of running a two-piece front DS was to use a pillow-block style carrier bearing (like the one in the rear of my Chebby pickup). Some of the go-fast guys had problems with these because the grease overheats. Seems to be a potential problem with rear DSs too. For a little perspective, it would seem this same group has problems keeping grease in double cardans as well.

Now to give myself a little credit, I started designing a fixed-yoke, double-bearing setup in my head, but before I got too far, I googled it and found the go-fasters had anticipated me by around 2-1/2 years. So I didn't invent anything totally new, but the good part to learn was that I wasn't all wet, and racers have been using similar setups successfully. The other thing I learned was that the more successful designs were using tapered roller bearings in oil baths. I had fully intended to use tapered bearings, but hoped I'd get away with grease, since it works for my wheel bearings. Maybe not, since the DS spins faster.

Several vendors are now advertising these, but here's the earliest thread I've found on the subject. As far as I know this is the original. If you notice, he started with a zerk, but mentions abandoning grease for gear oil.
http://www.pirate4x4.com/forum/gener...aft-vibes.html

EDIT: This thread from 2009 is actually the oldest I've found, I just hadn't realized that:
http://www.pirate4x4.com/forum/gener...l#post10305755

[aw12345]

I had seen that at one time or another, way more trouble then it's worth, then there is still the thing that driveshafts should not run at more than 8 degree U joint angle. As fancy and good as that solution is I think the stock pillow block bearing of a 1 ton pickup is a better solution at the speeds you will travel provided the driveline angles are reasonable. They last several 100 thousand miles in pickups. Big rigs use a larger version that generally last close to half a million miles or more without any maintenance . The thing that lills em is running steep driveline angles to get around engines and crossmembers. In your case a set of warn hubs for your front axle would be a very good idea.

[inVERt'D]

That's more or less what I was saying about the pickup truck pillow blocks. From the factory basically 0* angle from the output. It's not that it's bad tech, it just has its limitations.

If clocking my t-case front output down doesn't work out, I think the fixed yoke carrier is my best bet. One thing that will work in my favor with the front output is that my driveline angle is almost flat--the output yoke will not be pointing up like most do. Also, that sketch is not to scale. Even as it is, the angle of the first shaft would be fine with the fixed yoke setup. If that's the solution that gets me where I want to be, then it will be worth the trouble. My second/ lower shaft will still be longer than the stock TJ rear shaft even with the HP 30. At any rate, there's a solution. At worst, if it doesn't work out, oh well, I got more practice designing and building stuff out of old scrap metal. It's a hobby. Keeps me sane. Sorta. Until I prove myself wrong, the front crossmember is a go.

As for lockouts, that would be a last resort for me. I don't like them.

[inVERt'D]

Back to the progress. This thread is still a few months behind.

Main parts of frame brackets welded and trimmed. The angled parts face inboard. The larger parts sandwich the frame rails. I had intended to trim the one on the left like I had the one on the right, but forgot to scribe the additional lines before I cut. Oh well, it will work. The cut outs are to where the crossmember goes in.

I welded the crap out of them. The joints were V-notched, first pass 6011 for its superb penetration, and a second with 7018 for its weld quality and the strength of is alloy. Can you see the distortion? They're allowed to do that. They're not allowed to break.


Here's a bracket with the 3/8” side plates and bolts mocked up.


Crossmember tubing cleaned up pretty nice. Bo (or should I say “Beauregard”) dropped in for the shoot...


...and to remind me about dinner. He calls this look “Blue Steel.”


Well, that's what I get for naming him Beauregard.

[daniel_buck]

You are a mad scientist! :-)

[inVERt'D]

You are a mad scientist! :-)

Yeah, but more mad than scientist

[inVERt'D]

Of the things I've made for the Jeep, this crossmember easily has the most individual pieces. I'd had the basic design already worked out before I started cutting, and once I'd settled on the tab configuration, the particulars kind of came in a rush. A big part of the fun has been watching the vision come together like a snowball. As of now, the crossmember has been basically complete for for over a month. Over the past few days I've been making some additional gussets and pieces, bringing the talley of individual, hand-fabricated parts to 50 and climbing. Some parts of the design are required, some are optional, and all have a priority level of sorts. Depending upon how many optional mini-gussets I add, there could easily be 70 or more individual parts welded to the crossmember before it's finished. :geek:

One of these days I'd like to get my hands on some good 3D CAD software, but until then, I'll have to settle with staring off into space slack-jawed. Not that I mind that.

Welded the two main tubes together. At this point I'd like to share a little story about distortion. You'll notice the bolt sleeves. Those were welded in-place after the two tubes were at least tacked together and perhaps had one pass of hot 6011 between them (I don't remember for sure). Those tubes didn't have much wiggle room, but just to be sure I welded them in-place (from the inside) with bolts going through them and the tight holes of the 3/8" thick brackets. Everything lined up. You'll notice from the earlier pics that this tubing has large radii on the corners. I figured I'd more or less fill it up. After doing the first passes with 1/8" 6011 at probably 160+ amps (don't recall exactly), I went back with two more passes of 3/32" 7018. Now here's the kicker: when it had cooled, the bolt holes were about 1/16" closer together . So there's a lesson in distortion for me :homer:

So, not the prettiest welds, but the joint is stupid strong and deep, and will be covered up anyway.


Locating the tabs. I'd already had them tacked on, but as I alluded to before, the vertical parts were getting in the way. I reconfigured them so the inners had no verticals, but rather flat shelves on the fronts, and the outers had verticals in the rear.


Welding on tabs. For awhile, I'd seriously entertained sleeving the lower tube with some 1-1/2", 3/16" wall tubing, but decided that would be unnecessary weight by the time I'd done everything else I planned. Welding 1/2" thick tabs to 1/4" thick tubing with substantial welds is going to distort the tubing some. I paced things to help control the distortion. Again, I beveled out the joints where I thought helpful; first passes with 6011 (burns very deep), and second with 7018.


A couple of observations about the crossmember core. Where it necks down it creates a stress concentrator or "riser." The control arm brackets are where stresses are going to be transferred to the crossmember, and they're right there at "neck". The control arm brackets being low as they are create a lever arm on the crossmember tubing. We can visualize the twisting forces this will put on the link when the weight/ inertia are trying to push the front wheels back. So, this stress riser needs to be dealt with. Material will be added to reinforce the neck as well as the entire crossmember, and distribute the torsional forces more evenly.

Found this rusty old 1/4" still plate laying around. Was a good find, but boy was it rusty and pitted. As you can see from the shape drawn onto it, it will be a laminate for the entire front of the crossmember. There will be complementary gusset-laminates on the rear, but clearance with the transmission won't allow one comparable to the front. Note also the flat tops of the control arm tabs.


Here's the front major laminate cut out and mocked up. Part of the leftover from that will be used as a reinforcing rib in the rear. Keyed between the front major laminate and the tops of the inner tabs is the front reinforcing rib: 3/8" thick and 2" wide. It's one of the few pieces of the crossmember that I bought new. I originally had in mind to use it as stock for custom tabs, but the entire thing went on the crossmember. As you'll see later, the wedges I cut off the front were used to gusset the rear of the LCA brackets. The symmetry was beginning to flow. Note how the neck has been reinforced. The new vertical neck-down (necessary for drivetrain clearance) corresponds to the horizontal widening.


Front 3/8" rib from the top.


For optimal strength, the end caps needed to be welded on before the laminates.


More on its way...

[inVERt'D]

Scrappy the Jeep gets some more cowbell

Lots more scraps to weld together. I've never been into naming automobiles, but I think around this time I decided to name my rig Scrappy.

Made a laminate for the back and a fish plate for the top. Later made copies of these for the other side.

Made gussets to go between the LCA brackets. Used a bender board techique for the curves. This is easier if your clamps have the same size foot (for lack of a better word).


Both of the gussets mocked up. I decided to open up the rear gusset a bit more, because, you know, it's all about ground clearance. :homer: Those two little 3/8" wedges on the deck there will be gussets in the rear.


Although it was too small for the front gusset, this Olympic plate turned out to be the perfect size for the rear. Checking it here--fit like a glove!


Decided the front gusset needed some cowbell. It's not welded yet there, just posing.


Stitch welded on the front stiffener and the rear stiffener, along with those wedge-shaped gussets.


Another shot of the rear stiffener. The front of the belly of the 4500 tranny has a pretty decent bevel in it, otherwise there wouldn't be room for that rear stiffener. Yup, it's tight up in there.


At this point I was mostly stick welding, but I did some selective MIG'ing too. I would have loved to TIG the whole shebang, but I was really low on argon and I was thinking I'd save it for welding the bracketry to the frame. The other issue was the rustiness of some of the material. There will be TIG, though.

A view of some cowbell. I did a little welding here and a little there, because although I figured some distortion was inevitable and acceptable, wonking out was not. This was a tricky design on account of the distortion issue.


If you'll recall the drawings, these 1/4" thick flat pieces on the ends will be bolted up to the bottoms of the brackets at the bottoms of the frame rails. They're welded all 4 sides, and even plug welded. Looks kinda neked though, don't it? Like a cow without a bell, if you ask me.


Got some cowbell coming right up...

[6spdYJ]

This thread is like opening an erector set, lots of metal pieces, lots of holes. Can't see what it is yet, but when the kid's done playing with it I'm sure it will be cool

[inVERt'D]

Glad you're enjoying it, Ted. Metal erector set? By the time I got mine in the '70s they were already plastic--bolts and all. I remember my dad telling me about the old school metal ones when my brother and I unwrapped it. I wouldn't mind having a metal set now, come to think of it. Hmmmm...:geek: