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Norwegian

Trad climber

dancin on the tip of god's middle finger

Mar 24, 2015 - 04:08am PT

your condition is
governed by block shear failure
at the hole from which the test
weights are hung.

this is a function of the angle
thickness, as well as the distance
from the hole to the edge of the angle.

also consider the placement of your
three holes: (2) at the bolted connection
to the main member, and (1) at the test weight.

i assume the test weight is hung
from the center of the 48" long angle, 24" from each end.
with your attachment holes 2" from the end,
your angle is subject to a simple span
of 20", with 1500# load at mid-span.

solve the beam diagram for the required
angle-moment-of-inertia.

make sure that the reactions (#) at the
bolts do not exceed their assigned capacity.

and then double check the resulting
angle thickness / leg size for
block shear capacity

ionlyski

Trad climber

Kalispell, Montana

Mar 24, 2015 - 08:58am PT

Thanks for that Norski. Wait a minute, I'm Norski.:)

OK, you pretty much busted me. I am not a structural engineer and have (safely I think) bluffed my way through a 30 year career by over designing/building. I'm a punter.

So if you tell me I can do it with 2X2X3/16's, I'm gonna make it with 3X2X3/8's. Can I?

Actually, there are four bolts employed, two as you say near the ends 2" in from the end and 1 bolt on each side of the beam flange 2" from the end of flange. Then the load is equal on each side of my angle.

Arne

Reilly

Mountain climber

The Other Monrovia- CA

Mar 24, 2015 - 09:04am PT

ionylski, the germane question for me is why are you on the hook for this call?
Did the architect punt to you?

ionlyski

Trad climber

Kalispell, Montana

Mar 24, 2015 - 09:29am PT

Because I'm rigging my gear frequently sometimes fixed, sometimes temporarily.
Implementing a new idea and had hoped I could avoid taking the project to a structural engineer for something I believed should be fairly simple.

I thought this could be fun taking it to Supertopo and see what kind of reactions I might get or how scared I can make people.

Arne

Edit: And I just lost my father this winter, an architect and structural engineer his whole life, who I used to bring these problems to for solutions.

nah000

climber

no/w/here

Mar 24, 2015 - 09:40am PT

^^^^

i will be your huckleberry, in part..

build a relationship with an engineer and that's a <$500 question... build that into your price and you're good to go.

or come on supertopo and tell us it's to see what kind of a reaction you'll get, playing some for schmucks and end up making yourself look like a shady fly-by-night contractor...

interesting professional choice you are making.

edit in response to your edit: i'm sending a pm with input that is less snarky. genuinely sorry to hear about your loss.

Steve Grossman

Trad climber

Seattle, WA

Mar 24, 2015 - 10:24am PT

Arne- I am also sorry for your your loss.

As long as you don't ask an engineer to design something for you and keep your assignment to component sizing you will get the information that you need without exposure. Design skill and engineering skill are distinct and the one doesn't presume the other.

It is always challenging to establish an efficient course of dealing with somebody new. Having your father fill this role too was easy but you definitely need to line somebody else up to do the work now that things have changed.

StefanS

Trad climber

Leavenworth WA

Mar 24, 2015 - 12:31pm PT

Hey Arne Sorry to hear about your dad, sounds like a great guy.
I am not exactly sure how this is configured from your description.
If the 4' angle steel was equal cantilever each side of the beam below, and had 750# at each end. A 3" x 3" x 5/16 angle would support that with a small margin of safety. Why are you wanting 7X the factor of safety?

ionlyski

Trad climber

Kalispell, Montana

Mar 24, 2015 - 01:12pm PT

Thanks Stefan,

If you ever drive the Going To The Sun Highway to the visitor's center at Logan Pass or St Mary's visitor center you can see some of his work. Or conversely, he used to jump the big hill there at Leavenworth, a daunting hill to say the least.

As to the 7:1, I used to assume a 5:1 and in recent years have noticed manufacturers involved in the entertainment industry will often spec their gear at 7:1. I just want to have a good margin above SWL to accommodate any shock loading.

Arne

cragnshag

Social climber

san joser

Mar 24, 2015 - 01:57pm PT

How about hanging the load from a beam trolley? This one is lightweight and adjustable to fit the 12" wide flange. If you don't want it to move you can duct tape a couple of doorstops next to the wheels.

And when no one is looking you can zipline yourself across the room...

http://www.lewiscontractorsales.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=T17426&Store_Code=PAL&gdftrk=gdfV26118_a_7c3199_a_7c12391_a_7cT17426&gclid=CO33iPbtwcQCFciGfgod7WEAPw

If you want something a little more beefy, then get a standard beam trolley with the non-standard 12" width option:

http://www.harringtonhoists.com/products/pdf/catalog/PT_GT_rev7.pdf

johntp

Trad climber

socal

Mar 24, 2015 - 02:09pm PT

A sketch would help. Your description is confusing.

edit: Why not support the load off the wide flange rather than a separate angle?

Tvash

climber

Seattle

Mar 24, 2015 - 04:32pm PT

I can calculate that. Will get back to you when I have a moment (of inertia).

KabalaArch

Trad climber

Starlite, California

Mar 24, 2015 - 05:40pm PT

build a relationship with an engineer and that's a <$500 question... build that into your price and you're good to go.

TGT

Social climber

So Cal

Mar 24, 2015 - 06:33pm PT

http://bit.ly/1C93vqD

ionlyski

Trad climber

Kalispell, Montana

Mar 24, 2015 - 09:49pm PT

TGT,
Thanks but none of them are goin a do it.
A

Tvash

climber

Seattle

Mar 24, 2015 - 09:52pm PT

Is there a dimensioned sketch available?

ionlyski

Trad climber

Kalispell, Montana

Mar 24, 2015 - 09:54pm PT

Your description is confusing.

I don't really think it is. My description seems accurate.

Why not support the load off the wide flange rather than a separate angle?

Because I need to create two separate rig points from the one beam, that are 3 feet apart from each other. one in front of the beam and one behind.

Arne

StefanS

Trad climber

Leavenworth WA

Mar 24, 2015 - 10:54pm PT

Hey Arne
As you add strength to your angle steel to get to your factor of safety, you will add alot of weight by making the steel thicker. Angle steel isnt the most efficient shape for the kind of loading you are going to have.

If you can change that, I would recommend going to a W wide flange shape. It is much stronger in beam action than the angle L shape. You probably wont have such a heavy piece and it might be more stable in dynamic loading.

I am hoping to take my kids there this summer, it will be fun to check out you dads projects.

Thats so cool he jumped here BITD, its burly. Speaking of structure the big jump is getting pretty rickety.

Good luck on your project.

Tvash

climber

Seattle

Mar 25, 2015 - 08:08am PT

a 6x6x3/4 steel angle will give u a 6,5 safety factor, but without a sketch to verify your description thats just a shot in the dark. sketch, scan or pic, post. pretty simple. personally? i would never trust any analysis withoiut such a verification. verbal descriptions are not a sound way to communicate this kind of thing.

ionlyski

Trad climber

Kalispell, Montana

Mar 25, 2015 - 03:10pm PT

OK Tvash,
Thanks and I appreciate it. 6X6X3/4 does seem HUGE.
I'll try to put together a sketch, although my description is not verbal is it? I consider it a written description.

Arne

Edit-I did in fact fail Stickman Drawing 101. Really. I can't even draw a stick man.

Banquo

climber

Amerricka

Mar 25, 2015 - 04:44pm PT

Angles are tricky because they are not symmetric. Since they are an open section, they twist pretty easily. Since the center of rigidity lies outside the section, torsion is pretty much guaranteed. Most people use double angles so that there is at least one axis of symmetry. Unless you can resolve the torsion, they suck for spreader beams.

Caltrans falsework manual states that a c-clamp that can be tightened to 90 ft-lbs can be use to resist a force of 500 lbs in any direction. Use clamps and chains to lift. I've actually lifted heavy steel with C-clamps and chains. See appendix C-5
http://www.dot.ca.gov/hq/esc/construction/manuals/

Get a 4 point chain sling:
http://www.riggingwarehouse.com/products/LIFTSL01/LIFTSL01@@2e02.aspx

Or simply get a Crosby Beam Clamp:
http://www.thecrosbygroup.com/2014/06/18/crosby-clamp-co-offers-larger-size-beam-clamp/

Tvash

climber

Seattle

Mar 25, 2015 - 04:53pm PT

So's yer I beam :)

Tvash

climber

Seattle

Mar 25, 2015 - 04:53pm PT

Angle isn't ideal for the app, as has been noted.

Tvash

climber

Seattle

Mar 25, 2015 - 05:06pm PT

Woops. I had you cantilevered out 4 ft, not 2'

a 4x4x5/8 structural steel angle will give you 7 to 1 under that loading if you attach the load and the angle correctly.

See what I mean about the drawing? :D

A ruler and pencil works for making straight lines.

Norwegian

Trad climber

dancin on the tip of god's middle finger

Mar 25, 2015 - 05:23pm PT

my favorite constant
is the radius of gyration.

Reilly

Mountain climber

The Other Monrovia- CA

Mar 25, 2015 - 05:30pm PT

Janis Joplin was the Queen of Gyration. Jess sayin'...

Steve Grossman

Trad climber

Seattle, WA

Mar 25, 2015 - 06:47pm PT

I rather like the obliquity of the ecliptic...

ionlyski

Trad climber

Kalispell, Montana

Mar 25, 2015 - 07:44pm PT

Hey this starting to get fun. Thanks for working with me here. OK here's some clarifications.

Tvash-correct, not cantilevered 4 feet out but more like 18" each side of the edge of the flange.
Also in reference to the 6X6 seeming huge:
So's yer I beam :)
Yes, but my load isn't

Banquo, cool links. I do have several beam clamps similar to those, I think both 2 and 4 ton. But I can't use those for this application. I have to create these points from the top of the beam, not the bottom and I need to create these two different rigid points. Similarly I don't see how any of those 4 point slings can help me out.

A couple more challenges are that I typically only have about 4 inches between the insulated ceiling and the top of the I-Beam. I am using Wilton super duty c-clamps for attachment, rated at 12,500 pounds each. These are small clamps with an opening size scaled to my needs for this application. The spindle of the clamp is hardened and 3/4" diameter. Due to the restriction above the I-beam, the clamps will need to be inverted. This is why I started looking at angle. I am aware of the twist potential of angle. My first choice was channel but the inverted c-clamp will not reach over the side legs of channel.

Can I reduce some of the twist potential by moving the holes for the forged eye bolts off center, towards the vertical leg of the angle?

TGT

Social climber

So Cal

Mar 25, 2015 - 07:59pm PT

Weld a tab to the vertical on the angle. Drill a hole in it.

use that for an attachment point.

Two angles back to back with four clamps and a tab in the middle?

Those Wilton clamps are bomber. Clamp as close to the vertical leg as possible.

Clint Cummins

Trad climber

SF Bay area, CA

Mar 25, 2015 - 08:25pm PT

Your drawing is very good.
It's good to dust off those old skills that you weren't sure still worked!

Can I reduce some of the twist potential by moving the holes for the forged eye bolts off center, towards the vertical leg of the angle?

I think you are moving towards the suggestion of Banquo and TGT - weld a second angle onto the back of the first to resist the twist.
This is like the channel you wanted, but clampable.
I think you want the clamp points to line up with the eye bolts which suspend the load.
All could be closer to the vertical part of the first angle, but if you don't have it backed by the second angle, if the load swings past the vertical it might load the clamps a lot?

Similarly, if you can't guarantee that you load and unload both eye bolts at the same time, you load one of the clamps with 750 pounds multiplied by some torque factor at 2'.

Banquo

climber

Amerricka

Mar 25, 2015 - 09:00pm PT

You want to apply any forces through the center of gravity of the section. For the 4x4x5/8 mentioned above, the cg is 1.23" from the two outside faces. For your sketch, you will want the bolt holes and the clamps 1.23" from the outside face of the vertical leg and 3.77" from the free edge of the horizontal leg.

To check the bending stress is a subject not generally covered until graduate school. Summarizing an old textbook:

1) Locate the centroid of the section (from tables 1.23")

2) Calculate the moments and products of inertia

3) Determine the directions of the principal axes and the principal moments of inertia. With equal legs this is probably at 45 degrees.

4) calculate the bending moments and stresses in the principal axes. You have to divide the moment up to match the principal axes and calculate the extreme fiber distances.

Since the top edge of the vertical leg is in compression and has no flange, better check buckling. There is a whole series of things to check in the AISC specifications for buckling. It would take me a day or so just to figure it out. Buckling is notoriously hard to predict.

Why not use a rectangular tube and have somebody weld flat plates to it for your clamps? Maybe a 4x4x1/4 tube with two 6x6x1/2 plates welded to it for the clamps. Go to 4 clamps. Have somebody check the welds and stresses. Nice easy undergrad analysis. Keep your factors of safety to 2 - 3 or 4 if people are at risk.

Tvash

climber

Seattle

Mar 25, 2015 - 09:31pm PT

yeah, 4x4x5/8 will do the job. i'd bolt it to the i beam tho 2" inboard of the flange edge. knock one of those wts horizontally and those clamps could slip

Z = M/max stress
M = 750x(18)
max stress = UTS strctl steel/7
solve for Z
pick angle size to match Z
locate mounting holes per post above

if u must use clamps, add 4 more on i beam as hard stops to prevent rotation of angle

Banquo

climber

Amerricka

Mar 26, 2015 - 07:45am PT

Be careful, somebody could get killed.

Angle bending and torsion spreadsheet. Believe me, this seemingly simple problem is very complex.
http://www.excelcalcs.com/repository/strength/beams/single-angle-bending-with-torsion/

Local buckling:
http://www.steel-insdag.org/TeachingMaterial/Chapter8.pdf

johntp

Trad climber

socal

Mar 26, 2015 - 07:52am PT

I still question why you need a separate angle rather than supporting the load off the wide flange

Tvash

climber

Seattle

Mar 26, 2015 - 07:57am PT

Cantilevered angles don't appreciate having their loads sway back and forth perpendicularly. Not great in torsion.

ionlyski

Trad climber

Kalispell, Montana

Mar 26, 2015 - 08:32am PT

JohntP-How can you achieve two different points three feet apart from one beam? Not in the direction of beam travel but in perpendicular fashion.

Arne

johntp

Trad climber

socal

Mar 26, 2015 - 09:07am PT

Arne- your sketch doesn't show the loads. How do you intend to connect to the loads? I don't really understand what you are doing, but why not just run a cable over the wide flange beam?

Clint Cummins

Trad climber

SF Bay area, CA

Mar 26, 2015 - 01:16pm PT

The loads are attached to forged eye bolts, which go in the holes that are 2" from each end of the angle piece.
750 pounds on each point.
(Just read Arne's first post in the thread).

ionlyski

Trad climber

Kalispell, Montana

Mar 26, 2015 - 01:43pm PT

Thanks Clint for the clarification.
Yeah and the credit for the sketch goes to my daughter. No way could I sketch that but she forgot to show the forged eyebolts.

My chain hoist hooks attach directly to the eyebolts. I'll say it again, I can't simply loop steel around the beam for this application. The distance between the points and their relationship need to stay fixed at those dimensions. That's why.

Arne

ionlyski

Trad climber

Kalispell, Montana

Mar 26, 2015 - 02:28pm PT

I like the idea of back to back angle. Could I not simply bolt them together? That way too, I'd have 4 Wilton clamps involved.

What would be the best way to create a single eyebolt point , presumably in-between the two angles?

Arne

Clint Cummins

Trad climber

SF Bay area, CA

Mar 26, 2015 - 02:56pm PT

Always great to get help from the kids!

Would a U-bolt that connects to both angles be strong enough?
It would get you the symmetry.

Maybe better is 2 eye bolts connected by chain?

Not sure if you need to connect your load directly to the backing angle, though.
It might be enough to just use the second angle to prevent twisting.

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

Tvash

climber

Seattle

Apr 1, 2015 - 12:13pm PT

Oh, it was all good fun. Plus, who wants an engine on the head?

ionlyski

Trad climber

Kalispell, Montana

Apr 1, 2015 - 02:00pm PT

Plus, who wants an engine on the head?

Or one of my arrays!

Tvash

climber

Seattle

Apr 1, 2015 - 02:06pm PT

This is the closest I'll ever get to being a rock star.

BTW, I've got a BSME from Cal, but no PE license.

If it explodes, I don't exist ;)

It won't, though.

Banquo

climber

Amerricka

Apr 1, 2015 - 03:40pm PT

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.

One Chicago catalog I looked at rated the 1/2" for 2600 lbs straight and 650 lbs at 45 degrees.

http://www.chicagohardware.com/catalog/18_22_eyebolts.pdf

Another states 2200 lbs

http://www.chicagohardware.com/catalog/14_15_eyebolts.pdf

The second one also states that "Loads are based on a safety factor of 5 to 1." so there is no need to apply additional safety factors unless you are lifting people when, if I recall OSHA right, it should be 7:1.

Be sure to get quicklinks and bolts from reputable suppliers as there is a lot of Chinese junk coming into the country. I wouldn't be surprised to find Chinese knockoffs claiming to be Chicago USA.

I also have an MS in Civil Engineering. I do have a PE and I also taught structural engineering at a university for 30 years.

overwatch

climber

Apr 1, 2015 - 04:41pm PT

I work as an event high rigger and I have been following this thread but have hesitated to comment without knowing the structure you're hanging in. Is there some sort of extreme trim height issue that disallows you from bridling from adjacent beams?

ionlyski

Trad climber

Kalispell, Montana

Apr 1, 2015 - 08:21pm PT

Thanks Banquo and others. The angle on these shoulder bolts, which are aligned to take maximum advantage of the shoulder is probably more like 10 degrees and I can lessen that with longer bridles too.

Overwatch, yes extreme trim height is one of my reasons for this project. The other is to achieve front and back motor points from one beam, otherwise it's a pain in the asss to tether the array. And actually the beams are 20 feet apart from each other with zero rigging options in between. Bridling between beams wouldn't be an option.

Look, the two venues I will use these in are for events with MUCH smaller arrays than my outdoor photo above. In one, I can't even lift with motors due to low trim, so for years we've had to lift with Genies and dead hang right up to the beam. That one in particular uses 4 Vertec boxes per array totaling 500 lbs including motors at 250 per point.

Arne

Edit-And yes Banquo as I've always understood it Safe Working Loads which are stamped to the hardware are 5:1 above breaking strength.

overwatch

climber

Apr 1, 2015 - 09:47pm PT

understood thanks for the reply

Handjam Belay

Gym climber

expat from the truth

Apr 1, 2015 - 10:17pm PT

This whole thing took a turn into the 4th level of Hell when you said you were an audio guy.

We enter the 5 level of Hell when you add the outdoor roof structure.

Buy a roll of trickline and focus your cabinets that way.