Box frame at spring hangers only?

I never really had a desire to box my frame. Mainly because I don't want salt getting in there and sitting. Is it a good idea to box only where the spring hangers are? Maybe like a 4 inch wide piece of 3/16"? Or would this make it too prone to cracking and probably best left alone? I really appreciate any advice. :stout:

 

Your suggestion is exactly how the factory HD frame (such as used in my Renegade II) is boxed. I'll try to get some pics posted this weekend.

The stiffeners that Howard Eisenhauer used above are good, also. Notice how they are not filling the corners and they are only tack welded at the edges. There are probably many opinions here, but avoid welding in a stiffener with a full circumference bead as that can create a hard point and a possible crack start.

 

Like this.....

 

You do good work, Howard.

 

I like Howard's solution. Our project is a '69 DJ frame which was boxed from the front crossmember back to the front spring, rear hangers. When I extended the frame I boxed the rear spring front hangers with the factory insert from another postal frame.
Regarding the front and rear hangers (shackle ends) I plan to cut a piece of one inch square tubing to fit between the flanges vertically positioned diamond-wise with a vertical bolt to clamp it together, not welded. Does that make sense without pictures?

 

Ditto, I think I'll mimic that idea.

 

When I bought my '67' (in late 66) the dealers son did a lot of Jeep racing. They had a lot of tricks to make the vehicle tough. They welded a plate to the bottom of the oil pan, they welded 1" square stock to the bottom of the spring U bolt plates so rocks wouldn't break off the bolts, and they boxed in the frame at the spring hangers.

(I live in New Mexico, so salt isn't much of a concern. Water is so rare here that I don't worry about it either.

They suggested I do the same on my new Jeep. I told them to go ahead.

So far, so good.

John

 

Mine's boxed front to back with a stitch type weld. Working good with no hassles as of yet. I do like Howards solution also. When I had mine done, I figured I wanted the frame stiff and let the suspension do the work. Many different methods I suppose.

 

My factory bump stop frame stiffeners are the same way. These are a smaller section and really don't create a hard spot which might be typical of hanger locations. It's probably rare that they even get loaded from stopping a total spring flexure. In my case, the rear tire is rubbing the inner fender before the bump stop is contacted. R)

I try to be careful with frame design advice. I've had some training with structural anaylsis and work with frame loading for other types of vehicles. I've seen bad Jeep frame repairs and modifications that work well, and I've seen what should have been good modifications cause more trouble, too. Working with old Jeeps seems to be a continuous learning experience!

 

reviving an old post...

SEE WHAT HAPPENS HWNE YOU USE THE SEARCH FUNCTION!!!!!

I think this is a great idea and much more intuitive than strapping the whole frame..
In preparation for my inevitable protective coating I am planning on doing all my welding and fab work in short order..

If anybody is still around who had done this before are there any suggestions for where to place the vertical braces?
I have a 73 CJ… Not planning on jumping it over rocks… but might try and crawl a few here and there..

 

It's funny how you think of a question, and someone posts the same question with a picture that you could swear came from the Jeep frame sitting in your yard! My frame that I bought last year had the spring hanger reinforced like that picture, and I was wondering if I should cut it off? I like the way that Howard reinforced his hangers.... did you have to bend the metal yourself or is that a stock piece of steel?

 

I did my frame just like this at the rear spring mount. It's been holding up well for years. Not cracks at all.

 

I liked the way Howard did his frame.. makes more sense to me, but I’m not exactly a structural engineer.
It would seem to me that the plate would cause more stress over a shorter span than the vertical reinforcements...

Either way I am looking to add a little bit more beef to my frame for the long haul... just want to do it in the best way possible

 

anybody ever "fish plate" their frame rather than go inside the C or box? seems it would cause less stress

 

Stress is everywhere and the only proper way to cancel or help the stress is to triangulate the joint or point of stress. I assume you are asking about doing a "Fish Plate" on the outside of the frame rail? ............which at that point would really have no effect on the integrity or strength at the spring hanger.................by adding the vertical plate above the spring hanger inside........... it's effect in theory is to cancel the flex in the bottom leg of the open frame rail............another way to do that would be to add a longer plate that has angled sides going to the top rail...........thus spreading the force over a larger area............Hence why some just opt to box the complete frame on older Jeeps as Jeep engineers did later in its evolution.

 

I think the main reason for not boxing the frame completely is that you lose a lot of the flexibility of the rubbery CJ frame. The springs are stiff and the frame is flexible - you really see that when it's flexed out.

When I think about reinforcements like this, I try to think of how the new material changes the rigidity of the frame, sp. where the stress risers now are. When you have flexible into rigid, the transition between the two regions causes a concentration of stress, often called a stress riser. This is why the frame rail cracks next to the relatively stiff spring hanger. With this kind of plate



you have remedied the rotation of the spring hanger along the axis of the frame, but you have created a stress riser at each of the corners. This is due to the stiffer boxed frame section transitioning to the open frame rail. One advantage here is any added forces from the rotation of the spring hanger is spread over a long section of the frame. With D-plates like Howard shows, the rotational force is more concentrated, but his design gets a lot of strength by triangulating the stress from the bottom rail to the web of the C-channel. IMO that's a better design. You probably don't even need to connect to the top rail - just a triangular gusset to the web may be enough to keep the rail from rotating at the spring hanger.

Also, another rule is that you are not supposed to weld across the rails, perpendicular to the long axis of the frame. So both of these approaches satisfy that. The plate only has welds parallel to the rails, and Howard's plates are bent at a right-angle so they too are only welded parallel to the rails. Welding to the web is ok.

Just a few thoughts ...

 

Tim..............Good points......but in my experience Flex equals stress , which work hardens the joint, which ultimately equals cracks. Just part of the equation of owning an early Jeep.
Personally I think a better approach is to have a more flexible suspension system so that most if not all of the flex is at the spring and not the frame.

Of course we are talking about 1940's - 1960's engineering technology in an early CJ frame up to 1972-1973...........not to say that it should not be used the same way for which it was built , with a 4 cylinder, and 6 inch wide tires!

But if you opt to have larger tires , more Horsepower , lower gears and lift then perhaps that old frame also has to evolve some to also meet those new challenges.