Truck arm set ups. Let see them.

While I cannot say with absolute certainty, I do not believe the stock "truck arms" are tempered steel, like spring. Most metals, certainly ferrous, have a degree of natural "springiness" to them and tend to return to their current shape when not bent too sharply.

I have a set each of OEM GM, and Stock Car Products fabricated arms, and do not think
either is made of more than a good grade of mild steel.

However, shortening them will reduce distance over which the twist can be absorbed and result in a torsionally stiffer arm and if twisted enough, could result in taking a new "set" . I suppose it depends on how much shortening needs to be done. Two inches probably wouldn't matter much, but the greater the amount, the greater the negative effect.

 

As far as I know, they are conventional mild steel.

If you must shorten them, do it at the bushing end, not somewhere in the middle.

Shortening them where they twist the most will create a rigid line in the arm, where the weld is, and could potentially lead to adjacent cracking.

Shortening them increases the torsional spring rate, which does deminish intended function, and could lead to shorter life, due to metal fatigue.

Of course, that could just be an arm that went from having a 1,000,000 mile service life, to a 750,000 mile service life.

Hard to say.

Just make sure you start with arms in the best condition you can find.

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And I am still waiting for an explanation from the "experts" that make and sell rigid arm systems, with threaded adjusters, as to how the laws of physics don't apply to their products.

 

Something like this. MW

 

Those are not rigid arms. Ladder bars twist torsionally, just like truck arms.

 

Curry Enterprises also sell Johnny Joints in various sizes

 

Answer to post #63:

For the same reason that some solid mount a Jag IRS center diff to the frame crossmember and still add trailing arms.

 

That does not make any sense, and does not apply tho this conversation.

The Jag IRS will not work without the trailing arms.

Take them out, and you will have an awfully floppy suspension setup.

 

I THINK ALOT OF HOT RODDERS WOULD DO GOOD TO SPEND ALOT MORE TIME LOOKING UNDER CARS AT A JUNKYARD THAN GETTING SUSPENSION IDEAS FROM OTHER RODDERS.

 

I'm glad I came across this thread there is some great info and great craftsmanship here!

 

Not completely correct. If you keep the cage, you need the trailing arms as they keep the cage from rocking (cage is mounted on soft rubber mounts) and they also provide a modicum of rear steering.

If you do not use the cage, then you do not use the trailing arms as the lower fulcrum arms are solidly mounted with tapered roller bearings so adding trailing arms introduces interference motion. The lower fulcrum arms are beefy and center mount points are wide; they are not at all floppy.

The only exception is if you add trailing arms that are pivoted up front on the axis of the inner fulcrum bearings. This is sometimes done on hi-perf road racing Jags that retain the cage.

 

Now tell me how this pertains to the thread.

 

You were citing common fabrication errors. I added one to the list. Simple.

 

Ahh. Thanks for the clarification.

 

NP.

 

I always pretend my project needs to have 20" of articulating suspension but I only use 4" of it

 

Maybe you don't, but...

 

My 67 bronco used to do pretty good but then I killed it...been sitting now for over 5 years...

 

A joint can move in any direction. It will not compress and I Don't see that as a problem.

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Joint movement is not the problem with a rigid arm setup.

 

Even square or rectangular tubing will flex some over a long length. Thick tubing won't flex as much as thick of course. I wouldn't use anything real thick, or too thin. 10 gauge is right at 1/8" thick and should be stiff enough and still flex a bit. It won't break unless it flexs a lot. I'm thinking of using 1 or 1.5" wide and 2 or 2.5" tall mild steel tubing with rubber bushings. The arms will be 5-6 feet long and angled in, should work well.

 

farna -

For the best results, I'd copy the originals (and NASCAR).
I did in mt Studebaker (Conestoga) and am very happy with the results.

ANY tubing it too stiff for good roll transition. Unless you don't want the suspension to work as well as it could.

Mike

 

Yup, but what do I know....

 

Been working on my 50 chevy truck for a while, there's more pics in my build thread. But I used factory truck arms and crossmember and rear mounted panhard bar.

 

Jimenez Bros Customs

 

No flex in square tube arms. Bad engineering.

 

take no offence to this but I dont know if i would tow anything with that set up. I have always followed the rule of thumb not to c notch a frame more than 50 percent of its height and be fully boxed.

Godspeed
MrC.

 

I have used truck arms on circle track race cars on and off for many years. Just to add about the discussion on flex. . While the were clamped on a surface plate I welded the seams top and bottom on a set of arms. I then installed them in the car. Same set up. The thing would not handle like it did. I was told the extra stiffness of the arms was the problem. The next week I installed a junk yard set and the car drove great. Same tires and same set up. If I had not done this I would not have thought it would be so. ................................ Many years ago a friend used truck arms to make ladder type traction bars for his drag car. The were mounted paralial to the frame. Back to a very good discussion

 

I ran across this a while ago, looks like a nice product line.
http://www.hotrodstohell.net/truckarm/truckarm_index.htm
We used to run them in Chevelle stock cars too, just like they came out of the truck except using spring buckets.