2 Ton Jib Crane Design Questions.

Looking at cranes that meet these specs show a 16" mast diameter. Page 5 on the following pdf : https://www.gorbel.com/resources/products/jibcranes/Documents/Jib%20Brochure2010.pdf

Ah! I see. But what are their tubing wall thicknesses?

Looking at their specs and design that makes sense but they have a hollow tube whereas with a heavy walled tube with a reinforced concrete core would be substantially more difficult to bend so a somewhat smaller diameter would carry the same working load.

A buddy of mine has a big scrap yard and needs some work done one of these weeks so will see what he has for tubing in that size. 12" Vs 16" is not that big of deal to me.

That sounds adequate, but a lot depends on the mounting of the arm...

It would be similar to what is in the that brochure link. Arm and load bearing point at the top with bracing and rollers going 30" - 36" down the pole.

Nothing fancy.

Super! And a rare Tcmtech GA award for your efforts!

I checked my math manually, the pipe diameter in my previous answer was 14".

For 12"; I=231 in^4, so max stress for this is 14922 PSI ~ 2.1 safety factor for 32000PSI steel.

If you want to "fish" for yourself: For Pipe I= Pi*(D^4-d^4)/64 (D is outside diam in inches, d is inside diam).

Max stress is M*c/I were M is max moment, c is neutral axis distance (6" for 12" pipe) and I is second moment (convert M to inches as 48000 lb-ft is 576000 lb-in). This is the one equation I have stuck in memory for beam calculation. As it computes the stress in beam.

Sorry, my good answer was wrong.

All I was going to say is you would need a 20 ton crane to take this down if you ever had to if filled with concrete/re-bar.

4000 lb at 14' is a lot of moment alright as shown by others. How deep are you going to anchor?

My backhoe can go down to just over 9 feet so that's as deep as is possible. Realistically with the 20' tube section plus the top bearing assy I figured just over 6 feet would be enough.

~30" dia hole filled with concrete in hard packed glacial loam soil. The intent is that well after I have gone and turned to dust it will still be standing!

Thanks.

I got to looking at things and the old electric commercial hoist I have is only 1500#'s single and 3000#'s double line rated so that's obviously going to be my lift limit now.

The mast won't be a flat plate bottom with anchor bolts into the concrete design though. It's going the full 6+ feet right in the ground one concrete pour. Once its there its a permanent part of the property.

Given that the ground where my shop is at is a mix of heavy glacial loam and clay and some pretty hard stuff to dig in with no real give to it like the sandier soils we have lower in the valley have. From personal experience even a 8" dia tree that gets it roots into it is anchored well enough stop our 14 ton dozer dead in its tracks and has to be cut down and dug out. Anywhere else I can just push one of those over root ball and all like nothing.

Eventually a 5" - 6" thick concrete pad will be poured in front of the shop but not this year or any time soon.

It's my home shop not a commercial one and for me anything that calculates at over 150% lifting capacity is safety factor enough for me to sleep well at night so 3x plus is just wasting materials unless I already have them on hand. I'm by nature not a worrier so until something gives me reason to be concerned it is not a concern.

I trust the math and I trust my fabrication skills but if I can find a 16" tube for the mast I will use it but if not and I can get anywhere between 12 and 16 I'll call it good and more than sufficient for the work I will do with it.

Bigger is always better....