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Tvash

climber

Seattle

Mar 26, 2015 - 03:38pm PT

Hang 2 back to back 4x3x1/4 angles (long axis vertical) from the bottom of the I beam. Cut a hole through both 3" flanges of angles to hang load with a 1/2" screw pin shackle (2 to 3 ton rating).

Locate center of load mounting hole for screw pin shackle a minimum of 1.5" from bottom edge of angle flange.

Still more than 7 to 1 SF with regards to shear failure or crushing at load attachment point on angle flanges.

Bolting the angles to the I beam with 1/2"ers recommended. I don't know how to analyze clamping in that config.

ionlyski

Trad climber

Kalispell, Montana

Mar 26, 2015 - 06:28pm PT

Clint, Yeah I think the two forged eyebolts and short steel stingers to one eye would be better. U-bolts I don't think are high grade, certified and acceptable rigging hardware.

Tvash, I follow and that would be very simple as to running the shackle pin through the hole. That's creative! But, guys, I HAVE to rig this on TOP of the beam due to low trim height. Also, I'm not installing so no drilling through the building beam allowed.

So, right now I'm leaning towards back to back angle bolted together with grade 8 3/8" bolts, 6 of them down the length of the angle and two forged eye bolts at each end. I will loose maybe 10" by bridling back down to one point but maybe that's the way it goes.

Still listening and really appreciate the time and willingness to work on this. I'm not going to proceed with something dangerous. Someone else mentioned up thread about guaranteeing my load remains split between the two points and in all honesty I can't positively maintain that during the lifting process, so that is another consideration. I can try but I can't say I can insure that aspect.

Clint Cummins

Trad climber

SF Bay area, CA

Mar 26, 2015 - 07:51pm PT

Looks like a good plan. (I had noticed the U-bolts were mostly targeted to fastening pipes to things).
If only one end is weighted, at least you now have 2 clamps to take the load.
It would be one of the configurations that you would rate the system for and see what the safety factor is.

ionlyski

Trad climber

Kalispell, Montana

Mar 26, 2015 - 09:19pm PT

Best fix - Weld it!

Weld the backs of the angle together or weld the anchor rig point? Or both? I am a little more comfortable with using forged shoulder bolts than fabricating a ring of some type, with what I know not. Speaking of the U-bolt suggestion are there any of grade 8 type?

If I welded the angle back to back, how would I want to do that? Clamp them together, grind a trough on the bottom and fill that? And then run a bead along the top of the vertical legs down the length? Seems like bolting them together should be adequate doesn't it?

Arne

Tvash

climber

Seattle

Mar 27, 2015 - 12:02pm PT

U bolts aren't meant for that application - not advisable. They're meant for pipes where the stress is evenly distributed along their radius.

Slightly oversizing a single angle (from my suggestion above) is the simplest option presented so far - but I would strongly recommend using 6 clamps (4 hard stops to prevent rotation, 2 to do the clamping). Just make sure the eye bolt mounting hole is located at the centroid, as mentioned, to eliminate torsional stresses (other than those created by a swinging load).

Welding comes with a whole book full of engineering considerations - I wouldn't go that route unless you know exactly what you're doing. If you weld the angle onto the i beam or weld two angles together at their edges you're adding a weld at the point of maximum stress on the angle (best place to resists horizontal rotation) - the sizing of the angle will need to be upped to account for that.

If back 2 back angles are used, bolt them in several ODD NUMBERED spots (5 should do it) along their length at the vertical centroid - the point of minimum stress. Avoid bolting them within 2" of the edge of I beam flange - the point of maximum stress for the angle.

lemon_boy

climber

Mar 27, 2015 - 02:03pm PT

you would be way, way better off using an HSS section (square tube). like others have noted angles in bending aren't great to start with. having them double cantilevered doesn't help. i avoid using angles like the plague.

also, another thing to consider - are you going to be able to load (and unload) the 2 attacment points perfectly simultaneously? if not (which is probably the case?) just clamping it to the beam could be a problem.

given your scenario i would look at welding short pieces of angle, on each side of the HSS, and clamping the angles to the beam (assuming the clamping looks like it will work).

johntp

Trad climber

socal

Mar 27, 2015 - 03:02pm PT

I'm starting to understand. Consider using another wide flange in lieu of angle? Less opportunity for distortion.

Tvash

climber

Seattle

Mar 27, 2015 - 03:11pm PT

A big enough angle will do the job just fine. If no angle, whatever size will work, provide the math that shows that. That's what engineering is all about.

Clamping a square tube brings its own separate set of issues.

No free lunch here.

healyje

Trad climber

Portland, Oregon

Mar 27, 2015 - 07:19pm PT

I'd personally go with the back-to-back angles welded together. Square tube would be fine load-wise, but a pain to afix to the beam.

TGT

Social climber

So Cal

Mar 27, 2015 - 07:56pm PT

Geez!

BITD I would have gone broke If I hadn't figured out this one in about 15 minutes.

Fer cryin' out loud were talking 1500 lb, not 16 tons!

[Click to View YouTube Video]

ionlyski

Trad climber

Kalispell, Montana

Mar 27, 2015 - 08:22pm PT

God this is fricken great! You guys are actually taking the time to understand my problem. And I have learned through the process. I can't believe the sincerity and earnest efforts to help me with this. There are so many great points going on right now I actually have some selection options.

It is very true that as I grab my motor pickles and begin to lift the array that I have very little control in keeping the load equal. There could even be some swinging involved but really less and less as the load begins to climb. Motor bumps can cause a little shock loading too.

I'm kind of leaning towards back to back angle with 4 good clamps per apparatus. But Tvash's idea of over building the basic angle and then ensuring that they can't move through clamp stops is what I dreamed up initially in the first place. I just wanted input on what size of angle that might be but i think I could have sized it up "common sense like" anyway. It's the simplest and solves my forged eye bolt method too.

However, this has been great discussion and has caused me to give more consideration to problems like twist.

Thank you so much!

Arne

ionlyski

Trad climber

Kalispell, Montana

Mar 27, 2015 - 08:30pm PT

TGT, you're right. But I usually just guess and over build. My loads hang above people. And this one is a little different.

But I get what you're saying.

Arne

Edit: Where the feck did you find that Python clip? Hilarious

ionlyski

Trad climber

Kalispell, Montana

Mar 31, 2015 - 09:29pm PT

OK, well here's where I'm at. Getting ready to put to use. I ended up going with 3X3X1/4". The total length of the steel is shorter than I thought I needed, at only 30" instead of 48". So, on a 12" wide beam flange there will be just 4" cantilevered out to the forged eye bolts on each side. I think it's pretty stout for the job.

I used 3/8" bolts at grade 8, five of them in a W pattern, as you can see. The only trick, going back to back angle was using two eye bolts and bridling down to one point. Right now I have them oriented in line with each other and one thought was to use these 1/2" quick links to bridle. They are stamped at SWL of 3300lbs. I think my 1/2 ton chain hoist hook will attach to both quick links but I could also take it to a shackle (pin down) and then hook to the shackle. Any comments on that?

Or I could turn the eye bolts 90 degrees and then run the pin of a massive shackle thru both eye bolts. Not sure if I like that idea as much but not sure why. Comments on that?

In summary the unit will clamp down now with four active clamps. I'm thinking I don't really need the clamp hard stops with this configuration?

Arne

Tvash

climber

Seattle

Apr 1, 2015 - 02:32am PT

eyebolts and the quick links to be derated about 5% due to the angled load (which increases the force on them), so min rating is 2750 lbs. shackle rating 5250 lbs min for 7:1. if so you're good.

TGT's 'just shoot from the hip' approach is not only not correct, but dangerous. He's forgotten the 7:1 safety factor, which accounts for unplanned shock loading. With 7:1, the load is not 'just' 1500 lbs, but 10500...closer to the '15000!' than not.

Norwegian

Trad climber

dancin on the tip of god's middle finger

Apr 1, 2015 - 07:02am PT

i applaud the poise of iron.
it takes such a beating
without frown or smile.
it requests no fanfare
and endures no sagging esteem.

the inter-lacing of it's local elements
lattice into one pretty macro-dream.

me and iron, we learn from each other.

it teaches me that the moment
resists bending with it's own intertial will.

forever is too soon,
and never is not long enough.

i am on the outside
of this existence.
like imagine now inverting.

infinity implodes
and i am chuck, raised to the negative 1.

oh. and if now is the bowel of
time and most souls entertain
it's entrails shooting the tubes
in a fluid-state passage;
then i am a cyst upon
the see-thru intestinal walls,
killing the machine
as i hyper-reproduce
toxic thoughts and shout
them into the passing fray.

though i have no concrete purpose.

i only excrete i.
which is a disease.

if you put iron into concrete,
they well marry, and complement one
another's strengths;
at the same time compensating
for one-another's weaknesses.

iron's tough lesson:
i am the universal solvent.
and i found our structural dream.
the heavens are no longer safe.
and hell just got a retrofit.

ionlyski

Trad climber

Kalispell, Montana

Apr 1, 2015 - 08:18am PT

Never thought about a pad eye. You mean sandwiched between the Ls? That would require a different bolting scheme I'm sure.

Tvash

climber

Seattle

Apr 1, 2015 - 08:33am PT

So...some important considerations.

You need to use a shoulder style eye bolt, NOT a shoulderless (rated only for vertical loads)

The Chicago 1/2" is only rated to 2400 lbs - and derated to 2280 due to the angle. I think you read the wrong rating number on the table. This gives you only a 6:1 safety factor. Bump it up to 9/16" for 7:1.

DEFINITELY use the quick links. If you don't, the 1/2" eyebolt rating drops to only 650 lbs.

You'll also need to derate the screw pin shackle due to the angled load by 5%. For 7:1, you'll need 750*7*1.05 = 5500 lb rating. The right 1/2" shackle will give you 3 tons (and the wrong one 2) - so choose wisely.

Not a complicated design, but certainly not a '15 minute' design, either.

Pad eyes with a high enough SWL for your application are either designed to be welded or need 4 bolted attachments (2 in the seam), so that's probably not a workable solution here.

The simplest, safest approach would have been a single, correctly sized angle with a shoulder (to account for load swinging) bolt at the angle's centroid. More complexity introduces more failure modes.

ionlyski

Trad climber

Kalispell, Montana

Apr 1, 2015 - 11:45am PT

Hey Tvash,
Yeah I probably should have just gone with the single angle. That is what I wanted to do in the first place, except I would have used channel if I didn't have the space restriction. I think using four clamps in a perfect symmetrical fashion was what swayed me to the back to back angle. I felt like that was a little more redundancy.

I only use shoulder bolts, mostly Chicago. I think the quick links made a nice bridle with a low angle. My motor hooks fit nicely over the two of them. Perhaps I'll size them up.

Thanks so much for all your time and sincerity.

Arne