Long Arm thoughts....

Here's somthing a friend of mine mentioned to me, and I wanted to see what people thought of this.

If you think about it, homemade long arms using 2" round or square whatever you may choose will work with poly or rubber bushings at each end, as long as they're adjustable on one end. (keep reading)

The expensive end "Johnny Joints" or large heim joints provide extra articulation becuase they twist and ease the movement of your suspension.

If you think about it, to avoid the cost of buying the expensive Johhny Joints or similar flex joint... you can use rubber or poly bushing at both ends and get the same effect by backing off each jam nut allowing the threaded portion of the one end twist as needed.

Its impossible for the adjustable portion to back out while offroad, the LCA isn't going to turn more than a small amount when needed, but this movement is essentially the same effect the expensive joint provides.

Loosen the jam nuts when off road, 1/2 a turn or so.
Then tighten them back down if you have to drive on the road just to be safe? What do you guys think?

you could do this. I built my own adjustable short arms, with stock rubber bushings at both ends. These have been on my Jeep for going on 3 years now, and the only problem with them is that the threads have started to get sloppy. This is because I used ACME thread, instead of fine thread. I thought that the sheer size of the threads on ACME thread would make them super strong. As it turns out, more threads per inch (fine thread) is actually where it's at. I couldn't recomend this for a DD, as mine never sees pavement anymore, but for off road only, I couldn't be happier with the twist (and bind free movement) it provided. FWIW- I didn't use a jamb nut, and if I recall correctly, JKS lower arms are built very similar to mine. (coincidence )

I was thinking the same thing as long as you have plenty of thread left on the bolt. i don't see why you wouldn't be able to.

Generally this is a bad idea. The constant "pounding" on the threads would cause them to strip out or pull out completly. You would be better off running all rubber or poly bushings. Or simply spending the money on safe suspension joints.


Of course, you can do what you would like... but I can tell you that it is a bad idea.

I built my 4-link long arms (FT style) using 4 Johnny joints, buying all the steel (a lot more than we used)all the nuts/bolts, a little machining, and a 3/4" RH tap for less than $500.

For the lower arms I used a wrangler spring bushing at the axle end because the wrangler bushings slide readily into a 1.5" ID tube. I welded a 1 1/4" bolt to the johnny joint housing. I used a 1 1/4" coupling nut (not easy to find) and turned down part of it to fit into the arm tubing. a 1 1/4" jam nut keeps it all tight.

For the Upper arms i used another johnny joint and this time welded a 3/4" bolt to the housing and tapped the tubing directly. using angle and one extra piece of steel i made the "C" shape to bolt to the factory upper bushing on the housing. cut the upper arm tubing at an angle and it will bolt up fine. again a 3/4" jamb nut.

The brackets were made from 1/4" flat steel and welded together into 2 main brackets.

so with what it's gonna cost in steel anyway, why skimp on an extra 100 bucks at the expense of safety and convenience?

You wouldn't build a roll cage out of exhaust tubing to save some cash would you? (if you would, do us all a favor and go play in traffic)

Dingo

Bushings will bind in more than one plane.....sideways as well as twisting. Having articulating arms only helps the binding of the bushing from twisting, not from the arm moving sideways relative to the mount. One of the reasons that johnny joints or large rod ends are popular for suspension links is because they last so much longer than bushings even if the bushings are on articulating links. The axle wrap that is allowed as bushings wear out is not a desireable thing.

I would not recommend doing what you want to do as a way to get articulating arms. One poster already said that he wore out the acme threads in his homemade articulating arms, and those acme threads are going to be much stronger than the small fine threads as discussed....not the other way around. You do what you like, of course it will work for awhile. However, I would not like to see this idea presented on this forum as a recommended way to build an inexpensive arm that will work well over time. What works well over time are the products that have been developed for this very purpose, and they are worth the price we pay for them.

A friend of mine had an RE LCA on which the jam nut seized on the threads, and he never bothered to tigthen it down. Even with the flex joint on one side, this left the arm to twist on the threads like you suggest.
As previously mentioned, the threads wore out, actually quite quickly, and the two sections of the arm pulled apart. Luckily he was pulling into an off road park as it happened, or at highway speeds he would have had trouble. I ended up welding the arm back together (it's now an expensive fixed length arm) for him, so he could wheel the day and drive home.

If you're gonna do something like this, I sure hope it's not a rig that sees any street time. Like Dingo said, with the cost of the other materials, I wouldn't skimp on two flex joints.

Goatman said:

You do what you like, of course it will work for awhile. However, I would not like to see this idea presented on this forum as a recommended way to build an inexpensive arm that will work well over time. What works well over time are the products that have been developed for this very purpose, and they are worth the price we pay for them.

Click to expand...

Agreed 100%.

Before I got into building my own stuff, I ran a set of TeraFlex lower arms that have the articulating joint in the middle. I always had good experiences with them so when it came time to build my first long arm setup I was going to use a similar design.

What I eventually came up with is the only way IMO to make this type of thing last, and it ended up being more complicated than I felt was worth doing, so I just bought johnny joints for $40 each and called it good.

The setup I was going to run was very similar to the backlash adjustment nuts on the leadscrews on a Bridgeport mill, if that helps anyone. I was going to use large-diameter Acme threaded rod on the long portion of the arm, and then on the frame-mount side I was going to have two Acme nuts set down inside a piece of DOM with about an inch of space between them. The bottom nut would get welded in with some space behind it to allow the rod to come through. The top nut would be approximately positioned in the tube, then the threaded rod would be taken out, and the nut turned just slightly so that the thread pitch would be a little off from the lower nut. The idea here being that the backlash and slop in the threads would be taken up by the misalignment. The two nuts would help with bending stress more effectively than a single one, and in the space between them I was going to have a zerk fitting to fill the cavity with grease.

After looking at parts, labor, and effectiveness, a 2.5" Johnny Joint with one-piece forged threaded shank and all hardware for under $50 seemed like a really good deal.

Mark, I dont think it sounds like a great idea. I had 2 of my jam nuts come loose on my front control arms, and even with Krawler Joints the threads started to strip out, and if i hadnt caught the problem, I would have ruined my arms!

I'd look into a long arm kit like Rock Krawler sells that is just the arms and mounting brackets. You can get them shipped for less then $500 (possibley less then $400), and it would be much easier and safer in the long run.

Give me a call some time if you want to talk about your project, I have done alot of research on building mine on the cheap, I can probably help ya out with the built. Might even have some parts laying around you might need.

Yea, you guys are right. They'll wear out.
Aaron, hook me up! I need a single UCA!! You got a Krawler one I can borrow to copy the design? I'll give it back!

I only have the single upper(didn't get a new one with the new kit) but I can get you measurements and pictures!