Internal reinforcement in DIY backhoe boom?

[NearBeer]

Thanks for your time. I have access to some plate steel and have been sketching some ideas out for a stand alone mini-backhoe. Does anyone have any plans or pics of how they reinforced internally the boom? Seen lots of pics of a completed boom but none that shows where and what type of reinforcing pattern they used in fabricating the boom. Any help/advice is apprciated.

In search of my next cold one,

NearBeer

 

[J_J]

I am not sure what you mean by internal bracing. On my boom, each one of the rotating pieces had a DOM 1 in ID X 4 in tubing welded for the 1 in pins. On the bent section of the boom, 1/4 in steel plate was welded across the joint for reinforcement. It also depends on the thickness of the wall on the box tubing. For light duty, I believe they use 3/16. and 1/4 for med duty, and 3/8 for heavy duty in the DIY booms. If you have doubts about the strength of the tubing, you can add 1/2 in strap down all sides. I haven't done that yet, but might in the future. In my opinion, the box tubing should be 1/4 or better, and all end pieces and joints beefed up with 3/8 plate, with 1/4 in wall DOM tubing on all rotating joints, with grease fittings.

 

[NearBeer]

Forgive my lack of clarity in describing what I am trying to ask. If you were to take 4 equal width pcs of sheet steel and were to butt weld them to make a rectangular boom, would you add some type of bracing internally (attached to the inner walls/faces) prior to welding the final piece to complete the boom?

Still searching,

NearBeer

 

[kennyd]

No, the booms are hollow. Often a plate is welded over the butt-weld to reinforce the joint.

Maybe you should search for some plans instead of another beer

 

[J_J]

Butt weld a sheet metal boom , and lift WHAT????????

 

[NearBeer]

I haven't found the beer yet...wife is hiding it from me.

FWIW...not sure of actual fab procedures...my comment about butt welding was to better describe my question. Thank for the input

 

[Pooh_Bear]

You are talking about making square tubing?
And making seam welds?

If the steel is wide enough have it bent into a square channel.
Then weld the 4th side onto it.
Or have it bent into angle iron and weld two pieces together.
As long as the metal is thick enough I don't see why it wouldn't work.

Pooh Bear

 

[GT2]

I think he is refuring to fabricated booms etc. Like NH curved boom backhoes.
The booms are welded together from 4 pieces of pre cut steel plate ( not sheet metal! ).

 

[simplicityguy92]

you would have to stich weld the whole cuz of warpege and that would take awhile

 

[irvingj]

NearBeer-- from an engineering standpoint, you want to have as much mass as possible away from the axis of bending-- i.e., a hollow sructure. Unless you go for an intricate 3-dimensional internal triangle web construction (!!), you want to leave the inside empty.

 

[NearBeer]

Plate steel...sheet metal...cardboard...guess it might help if I were to use correct terminology

inrvingj...exactly the type of answer I was looking for! Thanks!

 

[Bedlam]

My guess and the way I took it was that he was wondering if there would be any benefit to weld some sort of diagonal braces of some sort INSIDE the tube as he builds it.If this is the case its an interesting one.Has me wondering why we wouldn't see more of them with an open concept like a crane boom.Most likely that would be too weak.
I would suggest using the heaviest possible material from the git go.

 

[J_J]

My guess and the way I took it was that he was wondering if there would be any benefit to weld some sort of diagonal braces of some sort INSIDE the tube as he builds it.If this is the case its an interesting one.Has me wondering why we wouldn't see more of them with an open concept like a crane boom.Most likely that would be too weak.
I would suggest using the heaviest possible material from the git go.

Lattice metal type boom??? I think it would be totally impractical. Has anyone seen a lattice built backhoe. You would have to be an engineer to develop the right spacing and angles for this type project, plus all the welding for all the little pieces, with the correct angle , cut to fit.

But, I guess it would be a fun project if you had time on your hands, and the equipment to cut and grind the angles and weld a couple hundred pieces of metal to form the boom design of your choice.

 

[zzvyb6]

Irving makes the bottom line point. The bridge/boom should have added section as far as possible from the shear center of the beam axis. That's why here is an "I" in I-beams. From a practical standpoint, a thickwall tube would be my suggestion for a boom candidate. Then add the gussets and shear walls.

If you are going to dig soft ground, pull up small trees for replanting, or bury a water line, you may not need too much added metal. Rocks, clay and concrete busting are another matter.

That's the engineer's opinion....