CR4 - The Engineer's Place for News and Discussion ®


Previous in Forum: Engineering Drawing   Next in Forum: Steel Wire Ropes Friction With Cast Iron Sheaves
Close
Close
Close
12 comments
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8125
Good Answers: 748

2 Ton Jib Crane Design Questions.

09/21/2016 9:37 AM

I've been cleaning up around the shop and I got to pondering on building a fair capacity jib crane for in front of the shop.

What I would like is it to be ~14' high with a 12' arm and up to 2 ton capacity at maximum reach.

Just not sure what colum pole dimensions I would need?

I'm thinking 12" - 14" dia 1/4" - 3/8" wall with a concrete and rebar core.

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Guru
Engineering Fields - Mechanical Engineering - New Member Fans of Old Computers - TRS-80 - New Member Popular Science - Weaponology - New Member Safety - Hazmat - New Member Hobbies - Fishing - New Member United States - Member - New Member

Join Date: Apr 2012
Location: Detroit MI, USA
Posts: 1701
Good Answers: 174
#1

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 10:19 AM

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

__________________
How we deal with death is at least as important as how we deal with life. --CAPTAIN KIRK, Star Trek II: The Wrath of Khan
Register to Reply
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8125
Good Answers: 748
#3
In reply to #1

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 11:38 AM

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.

Register to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 17678
Good Answers: 1009
#2

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 10:30 AM

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

http://www.ijrame.com/vol3issue1/V3i104.pdf

__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8125
Good Answers: 748
#4
In reply to #2

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 11:42 AM

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.

Register to Reply
3
Guru

Join Date: Sep 2012
Location: Iowa, USA
Posts: 559
Good Answers: 47
#5

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 12:52 PM

TCMTECH:

I used a program call beamboy. I simulated your 12" pipe with .375 inch wall thickness. I placed a 48000 ft-lb moment at each end (4000lbs * 12 ft), one clockwise at ground and one counter clockwise at 14 foot end. I had the program compute the second moment (I) for the beam using 30 million PSI modulus (steel) and with the 3/8 wall thickness came up with I=373 in^4.

It showed a max stress of 10.8 KSI which cheap steel is 32KSI so this would give a static loading safety factor of 3 without any concrete core.

Max deflection at 7 feet was 0.182 inch.

__________________
ignator -
Register to Reply Good Answer (Score 3)
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8125
Good Answers: 748
#6
In reply to #5

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 1:27 PM

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

Register to Reply
Guru

Join Date: Sep 2012
Location: Iowa, USA
Posts: 559
Good Answers: 47
#9
In reply to #6

Re: 2 Ton Jib Crane Design Questions.

09/22/2016 4:39 AM

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.

__________________
ignator -
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 10440
Good Answers: 128
#7

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 1:38 PM

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?

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8125
Good Answers: 748
#8
In reply to #7

Re: 2 Ton Jib Crane Design Questions.

09/21/2016 1:53 PM

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!

Register to Reply
2
Member

Join Date: Jun 2011
Posts: 9
Good Answers: 1
#10

Re: 2 Ton Jib Crane Design Questions.

09/22/2016 9:36 AM

We are an overhead crane company and install these jibs all the time. Reference charts I use, for this size jib, show the mast as 16" diameter, with heavier wall. Bottom of mast would have a flange welded to it with holes for anchor bolts. Two pours of concrete, one with anchor bolts embedded, then much larger pour ending up with 7' to 8' square base (depending on soil/concrete).

Cranes require safety factor of 5:1 for use in industrial settings. Soil pressure, concrete psi rating, #of anchor bolts, can all affect the design and size. A local Professional Engineer could help with this.

I'm a DIY type frugal engineer myself (and you are going to hate this answer) but IMHO, it's the usual scenario of risk of failure vs. peace of mind. You could "overkill" everything and hope for the best, or hire a PE to size/design it, or find a local qualified crane dealer (with good insurance), pay a little more, and sleep well at night.

cheers, flyingbrickz

Register to Reply Good Answer (Score 2)
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8125
Good Answers: 748
#12
In reply to #10

Re: 2 Ton Jib Crane Design Questions.

09/22/2016 11:02 AM

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.

Register to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 17678
Good Answers: 1009
#11

Re: 2 Ton Jib Crane Design Questions.

09/22/2016 10:49 AM

Bigger is always better....

__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Register to Reply 12 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Copy to Clipboard

Users who posted comments:

flyingbrickz (1); ignator (2); James Stewart (1); JPool (1); SolarEagle (2); tcmtech (5)

Previous in Forum: Engineering Drawing   Next in Forum: Steel Wire Ropes Friction With Cast Iron Sheaves

Advertisement