Part 2 - The Arms

So I did some surfing, did some reading, did some calling around, and ended up talking to Ben Olson at OTT Industries in Vancouver, BC, Canada.

The Dana 60 High Clearance Steering Arms OTT produce stand alone at the top of the pile in my opinion, and that's why I decided to order them.

What makes them the best choice - that's what I'll explain in this section

Features of the OTT arms include:

• CNC milled out of a single steel billet, no welded parts
• Integrated kingpin bushing cap with grease fitting
• Angle-compensated for steering axis inclination - allowing maximum possible steering linkage travel
• Precision machined to use stock Dana knuckle studs and mounting nuts (no long studs and/or bolts required) - assuring the tightest possible fit, the only way to develop the required strength for steering from the top of the knuckles.
• Tapered for your choice of 1 ton TRE, high angle drag link ends or straight drilled for rod ends / heim joints
• Designed to fit virtually any tire and rim combo possible including stock Hummer rims, large tires and rims with custom offsets or backspacing.

The following pics illustrate the arms and their features:

Part 3 - Installation and Testing

Before I detail the installation, I should mention my one "beef' with the OTT arms. My beef is this: there are absolutely no instructions of any kind included. I know, you're thinking: "big deal, they're just bolt-on steering arms". And for those of you smarter than a box of hammers, that may well be true. But I have a gift - if there's any possible way to screw something up - I WILL find it. And sure enough, there were several "gotchas" I fell into during my installation.

In retrospect, I don't believe any of the issues that I stumbled onto are issues with the product - but merely screw ups that all could have easily been avoided with an instruction sheet. Whether they are product issues, my unbelievable ineptitude that could only happen to me and are therefore of no concern, or just things that you're glad I messed up and warned you about - you will have to decide for yourself!

Alright - I've made several references to mounting style / hardware, and it's importance, so let's get into it.

First, let me convince you of why this is such an important consideration.

To begin with, this is one of, if not THE, most important bolted joint assembly on you rig. Why? Two reasons, really. One, because obviously the entire steering system, and therefore your control over the rig depends entirely on this joint. If it fails, you're in the ditch....or worse, for sure.

Two, because it sees comparatively large loads for the size and number of fasteners involved. The size and number of fasteners is limited by design factors of the knuckle (i.e. there isn't room for more or bigger fasteners), and that is why use of proper fasteners (made from proper strength and hardened materials), proper torque spec, and the 60° tapered seat are absolutely critical - just the way GM engineered it in the first place. Believe me - if they could have gotten away with simpler holes (non-tapered) and bolts instead of studs (less parts, easier to install) with the factory parts, they would have. There's a good reason GM elected to spend the money to engineer and assemble the way they did, (and why we should retain that design)and I'll attempt to explain those reasons.

The first thing we need to do is to understand just how a bolted joint works. This is a huge topic itself that, according to legendary mechanic "Smokey" Yunick; "To thoroughly understand it all would require at least 4 specific engineering degrees and 20 years of hands on experience in each". Rather than delve too deeply at this point, let's just state some of the basics. If you want more information, a good place to start is the basic tutorial from Bolt Science. For our purposes we must understand that:

• Technically speaking, SAE (i.e. automotive) fasteners (bolts or studs, and nuts) in a bolted joint are not designed to carry a shear load. They are designed to clamp the 2 parts together, so that the friction between them carries the load - or at least the majority of it. In reality - SAE fasteners do do this but also usually carry some load in shear.
• That in order to carry out their duty as "clamps", they must deform (stretch) a fairly precise amount upon installation / tightening so that the resulting force that tries to return the fastener to its original length achieves the clamping force. The most common and easiest way of approximately measuring this stretch (and thereby being assured that the proper clamping force is achieved) is by measuring the torque with which the fastener is tightened in the assembly, as this has a direct, mathematical relationship to the amount of stretch.
• Fasteners of differing "grades", materials, and construction methods (hardening, tempering etc.) have vastly different strengths, ranging from SA grade 1 bolts with a yield strength of 36,000 psi to SAE grade 8 bolts with a yield strength of 130,000 psi. This directly affects the maximum stretch that they can endure without permanently deforming, and therefore the amount of clamping force they can develop. We see this as different maximum torque values for different bolts. Hopefully , we now see this as not just "how tight do I have to do it up", but rather, "when I tighten this fastener, how much clamping force can I develop"
• And finally, because of fastener preload (explained well in the Bolt Science tutorial) a properly tightened fastener is vastly stronger than a loose sloppy one.

OK, so how big a load are we talking about then. Let's do some rough, back-of-paper-napkin calculations to get an idea - if only to get a rough order of magnitude and to convince ourselves that, yes, we better be pretty darn particular about how we assemble these joints (that is, with how we bolt the high clearance steering arms to the top of the knuckles).

So, if we plug in the following numbers, using my Wolf as an example:

W=2400 lbs, mu=0.35, B=14", E=6", we come up with a result on the order of 3500 ft lbs!!

Right - so you can't take that calculation to the bank, you can't design anything based on it, but hopefully it convinces you not to do a hack job and just bolt the steering arms on with any old half-inch fine thread bolts you have lying around.

Which brings me to my final point about using the proper hardware, specifically the GM studs and nuts.

What is the difference between a stud and a bolt? In the grossest of terms, the answer is nothing, both are merely clamping devices, as we have discussed.

However, there are some important differences, which are often critical in highly stressed parts such as this. They are:

A stud is frequently specified when one of the clamped-together members is an expensive cast or machined piece with internal threads - as is the case with the Dana 60 steering knuckles, especially if the assembly ever requires disassembly for inspection or maintenance, as is also the case with Dana 60 steering knuckles. This is because one wishes to avoid stripping the internal threads of the cast or machined piece at all costs - since repair may prove impossible or extremely costly. Each time an assembly is disassembled and assembled, one risks stripping or damaging the internal threads in the cast piece if a bolt is used. With a stud, one can tighten the stud in place in the cast piece, then need only remove the nut from the stud in order to dissassemble the assembly, rather than having to remove the bolt from the cast piece's internal threads; minimizing the chance of damaging the internal threads in the cast piece.

Also, in an assembly highly loaded in shear, as is the case with the steering arm to knuckle joint, the stud offers us an advantage as it will be full diameter (i.e. non-threaded), right at the joint interface, where the most stress occurs, giving us maximum possible strength in the fastener, and more importantly, the tightest possible precision fit between stud and hole. We desire a tight, precision fit in order to eliminate slop and play that would contribute to a weak joint. The OTT arms are a very tight fit on the non-threaded portion of the studs for this reason. A bolt does not offer us the same advantages, because either

• a) When tightened to spec either all, or a portion of, the shank that fills the hole in the steering arm will be threaded, and therefore a loose fit and weaker; or
• b) If we engineer the length of the bolt precisely so that the threads end just before the joint plane, as with a stud, then because the head of the bolt that we tighten is not free to rotate on the shank of the bolt, when we tighten the bolt to final torque we can not be sure whether the torque is rising due to the desired stretch being achieved, or simply because the threads have ended and the unthreaded shank of the bolt is bottoming against the internal threads.

Finally, studs can aid us in the assembly of tight tolerance parts in a way that bolts cannot, allowing us to set the part on the studs, and then sequentially toghten down the nuts, clampnig the parts together. Using a bolt in this manned can more easily lead to cross-threading the bolt in the hole.

It was a giant stroke of luck that at the time of this installation, my father, the genius mechanical engineer, happened to be visiting, so that I could explain each of my half-baked ideas for him to shoot down, before I had to knuckle under and go and buy the proper parts. You know that if he hadn't been, I'd have screwed up again, and a bit further down the page you'd be looking at my pics of a sheared off steering arm and three broken home-made studs and a grade 2 bolt with a lug nut welded on! Anyway, the results of our teamwork are (just in case you're tempted):

• You can't use regular grade 8 bolts - they will not seat properly on the tapered mounting holes, they have no provision for a tapered interface, and the threads in the steering arm hole are too loose a fit.
• You can't source a stud from somewhere else, you won't find one with 1/2-20NF threads both ends. All the 1/2" studs I found (such as Chevy big block manifold studs) were coarse thread one end. This will not do, since you can neither re-cut the internal threads in the steering knuckle to coarse thread, nor find a 60° taper nut (required to mate to the top of the arm) in coarse thread - they are all fine thread.
• You can't take a 1/2-20NF bolt, run a die right down to the head, and then thread it into the back of a tapered lug nut and think you have cleverly made a "lug bolt" (embarrassing picture of just such an aberration at left - bottom middle). When you went to tighten this into the knuckle, the nut that will rotate on the shank, combined with the head that will not will conspire to prevent you from achieving proper fastener stretch and therefore clamping force.
• You can't cut your own 1/2-20NF-threaded-each-end studs at home using a vice and parts store die set. The tolerances would never be right, you'd probably end up with threads inside the steering arm hole, and it would just be a flaky way to assemble the most critical joint in your rig. You could probably machine your own with the right tooling, training, and setup time, but by then you're saving nothing.

In other words - you simply have to use the GM studs and tapered nuts to do the job right.

Why the taper? Well, remember what I said about wanting to avoid any slop, looseness, or misalignment in the parts, as this would eventually lead to loosening and failure of the joint, both through loss of clamping force and subsequent loss of friction, and also component fretting and eventual failure?

No matter how well machined the parts are, if they are to be assembled and disassembled, there obviously has to be SOME clearance, otherwise you'd never get the parts together or apart again. The 60° taper seat in both the factory GM and the OTT steering arms, along with the tapered nuts, are the clever way of "removing" that clearance, as much as possible. As you tighten down the nut on the stud, over the steering arm, the tapered seats come together to achieve the tightest possible union that can still be disassembled easily. This is the same reason your wheels and lug nuts also use a 60° taper.

OK, allow me to summarize, and proceed with the actual installation.

***Use only the specified factory GM studs and tapered nuts for installation of these steering arms***

Phew - let's get on with it then!

I fully expect they will loosen and fall off! And with me being Mr Bean of the workshop - at least one will probably get sucked into the carburetor!

Note the marked up paint from the clamp used during installation. A by-product of not painting them early enough so that the paint could harden before I had to install them the day before a giant annual 3 day wheelin fest!

I expect you are beginning to see why I remarked earlier that I really would have appreciated some sort of instruction sheet - even for what appear to be "bolt on" parts. At least one should be included if these things are going to be sold to bumbling dim-witted three-thumbed garage monkeys like me!

Of course, being a military man - I have been rigorously indoctrinated with the mantra "Don't bring me problems, bring me solutions". So, with that in mind, I have created an instruction sheet for the OTT High Clearance Steering Arms, (it's really just a simplified version of this article) that may be viewed or printed from right here by current or prospective OTT customers.

You guys at OTT: Ben, Rick, Chris - feel free to save and print these and then include them in the box when you sell 'em - anything to help out my fellow Canucks! It is available in PDF

The following pics show the "final" installation in the Wolf, at least the first iteration. I was unable to move the tie rod up to the arms, as it would have then passed directly through where my track bar currently is. As I had hastily decided to install them the day before a major 3 day event, I simply didn't have time for the required re-design to make everything work perfectly. However, I was able to separate the tie rod and drag link, so at least I can bend the tie rod and just flip it around. Also, the drag link is raised way up so there is no longer any interference between it and the track bar bracket, so I am no longer at risk of tearing the track bar off again.