bending 4x4x.250 sqtube

[muddstopper]

My 1960'sRyerson steel data book says 4x4-1/4" weight/foot 12.51 and will take 14.5 kips @ 6'

10x2-3/16" is a pound heavier @14.65#/foot but will take 27.4 Kips.

Go skinny and deep may help with visibility and Welding the ends?

I dont think I want to go skinny simply because the sideways flex, especially if I bump something, might be more than the boom can take. I took a good look at the 4x4 tube I was planning on using, it seems it already has a pretty good bow in it. Most likely, I will endup buying new steel for the boom. The hub I am using as a base is 8.5in in dia, so thats what the inside distance will between the uprights for the boom/cyl mounts. I think 5 inch tube will be what I go with. I have thought about using 2x4 tube and doubling the tubes.

 

[Mark @ Everlast]

I have a local company that can bend metal and make special "C" channel out of 1/4" steel. They can add an additional lip (about 1-2" depending upon your requirement) on the open side of the "C" so that it partially forms a box. It comes out very straight and true. I used to work with a company selling Mazzotti backhoes, a three point hitch mount. You'll see them sold now under Taylor Pittsburg name. They were using at one time the same type of metal and welding them with with the open faces touching each other and welding down the seam. This makes for an extremely strong setup and these units offered higher breakout forces than any other in their classes. I've seen other companies do this too...

But on second thought....This same company employs a laser cutter and can cut any pattern at phenomenal pricing. I can usually buy from them something already cut and bent than I can buy the metal myself... You could probably find a company similar where you are. Have them cut you out a boom pattern with the pin and bosses and everything and weld it up out of 4 separate pieces. hmmm....that's an idea I need to file away when/if I ever want to start building backhoes....

 

[Mark @ Everlast]

I have a local company that can bend metal and make special "C" channel out of 1/4" steel. They can add an additional lip (about 1-2" depending upon your requirement) on the open side of the "C" so that it partially forms a box. It comes out very straight and true. I used to work with a company selling Mazzotti backhoes, a three point hitch mount. You'll see them sold now under Taylor Pittsburg name. They were using at one time the same type of metal and welding them with with the open faces touching each other and welding down the seam. This makes for an extremely strong setup and these units offered higher breakout forces than any other in their classes. I've seen other companies do this too...

But on second thought....This same company employs a laser cutter and can cut any pattern at phenomenal pricing. I can usually buy from them something already cut and bent than I can buy the metal myself... You could probably find a company similar where you are. Have them cut you out a boom pattern with the pin and bosses and everything and weld it up out of 4 separate pieces. hmmm....that's an idea I need to file away when/if I ever want to start building backhoes....

 

[muddstopper]

I have seen a few Utube vids of homemade loaders. Most, if not all, of those have been built using either 2x4 tube doubled to make a 4x4, or plain 4x4 box tube. Of course, 2x4 tube welded together should be stronger than 4x4 tube. If one is looking for maximum strength and loading tons of material, it makes sense to design toward those goals. Bigger tube= stronger boom. In my case, I am wanting light weight. This loader is going to be mounted at the front of the trailer near the tongue. Trailer is double framed 4in channel. Tongue fits under the trailer bed all the way back to the front axle. Even tho i think this trailer is good enough for what I plan on doing with it, its not exactly how I would of built it if special building it for this application. I have hauled a 9000lb tractor on this trailer before and even tho that was a bit overloaded for the axles, the trailer frame never flexed. Still, 9000lbs spread out on the bed of the trailer isnt the same as 1000lbs right next to the tongue. Add to that the weight when picking up a load, thats a lot of stress. While out riggers will be used when operating the loader, driving down the road that loader is going to want to bounce. I can already see me adding extra bracing to the tongue. I havent even calculated the weight of the processor that is going to be on that same trailer.

 

[muddstopper]

another try at autocad drawing up the boom/cyl mounting points. Did I mention I hate autocad??

 

[Xfaxman]

Kinda hard to see the drawing, so I cropped it.

 

[jb1390]

I dont think I want to go skinny simply because the sideways flex, especially if I bump something, might be more than the boom can take. I took a good look at the 4x4 tube I was planning on using, it seems it already has a pretty good bow in it. Most likely, I will endup buying new steel for the boom. The hub I am using as a base is 8.5in in dia, so thats what the inside distance will between the uprights for the boom/cyl mounts. I think 5 inch tube will be what I go with. I have thought about using 2x4 tube and doubling the tubes.

Quick and dirty analysis for you......

Ends near the base are fixed in place, the whole arm is 16 foot long. Loaded with 1000 pounds at the end.

Design 1 uses 4x4 x .25" wall.

Design 2 uses 2x6 x .25" wall

Look at the maximum deflection, and maximum stress areas near where the lower cylinder would attach. You can see that the 2x6 is better when loaded in this manner. If you add support arm above the beam like suggested, the capacity will be increased.

If I had a better dimensioned sketch and size pistons you are planning I could get you better numbers is to whether it'll work. Forget that autocad stuff, I found it more confusing than helpful.

 

[Sodo]

JB, what it that program you are using? Also only engineers know that 1.44e+000 = 1.44 inches. I think Mudd is using 2,000 lbs as his limit. Also I think Sq tube has yield str 74,000 psi

Mudd how much "bow" does your sq tube have? Could you orient it upward such that by self-weight it becomes straight?

 

[jb1390]

JB, what it that program you are using? Also only engineers know that 1.44e+000 = 1.44 inches.
Also I think Sq tube has yield str 74,000 psi

Mudd how much "bow" does your sq tube have? Could you orient it upward such that by self-weight it becomes straight?

I'm using solidworks.....and I meant to change that unit display to "floating" so as to not confuse the masses, my apologies lol.

The yield strength is going to depend on the material, not the shape. 50,000-75,000 psi is probably a good guess for most tubing without knowing the exact material.

Another note: just the tubing is 205 pounds. Add in mounts for cylinders, the cylinders themselves, pins, some kind of grapple at the end, and you're talking some serious weight. You want that tubing to be as efficient as possible to make this manageable.

 

[Sodo]

OK solidworks. I thought that was about $5,000 program & $thousands per year fees, am I right? I've looked into that and wished for it but can't justify it.

The yield strength is going to depend on the material, not the shape. 50,000-75,000 psi is probably a good guess for most tubing without knowing the exact material.

I read somewhere that garden-variety Sq tube in the USA is generally A513, ~74,000 yield strength. I've built stuff and tested deflection and found that (the rect tube I have access to) does not bend permanently at ~74,000 psi stress. I'm inclined to believe my supplier is providing A513. YMMV of course.

Can you run that deflection test with the main boom made with doubled 2 x 4 x.25 in? How about a 4 x 4 x .25 with a 4" x 3/16 flatbar doubler welded ontop covering 3 feet of the high stress area?