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Norwegian
Trad climber
dancin on the tip of god's middle finger
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Mar 24, 2015 - 04:08am PT
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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
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ionlyski
Trad climber
Kalispell, Montana
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Mar 24, 2015 - 08:58am PT
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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
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Reilly
Mountain climber
The Other Monrovia- CA
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Mar 24, 2015 - 09:04am PT
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ionylski, the germane question for me is why are you on the hook for this call?
Did the architect punt to you?
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ionlyski
Trad climber
Kalispell, Montana
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Mar 24, 2015 - 09:29am PT
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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.
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nah000
climber
no/w/here
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Mar 24, 2015 - 09:40am PT
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^^^^
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.
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Steve Grossman
Trad climber
Seattle, WA
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Mar 24, 2015 - 10:24am PT
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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.
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StefanS
Trad climber
Leavenworth WA
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Mar 24, 2015 - 12:31pm PT
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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?
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ionlyski
Trad climber
Kalispell, Montana
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Mar 24, 2015 - 01:12pm PT
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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
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johntp
Trad climber
socal
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Mar 24, 2015 - 02:09pm PT
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A sketch would help. Your description is confusing.
edit: Why not support the load off the wide flange rather than a separate angle?
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Tvash
climber
Seattle
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Mar 24, 2015 - 04:32pm PT
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I can calculate that. Will get back to you when I have a moment (of inertia).
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KabalaArch
Trad climber
Starlite, California
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Mar 24, 2015 - 05:40pm PT
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build a relationship with an engineer and that's a <$500 question... build that into your price and you're good to go.
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ionlyski
Trad climber
Kalispell, Montana
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Mar 24, 2015 - 09:49pm PT
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TGT,
Thanks but none of them are goin a do it.
A
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Tvash
climber
Seattle
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Mar 24, 2015 - 09:52pm PT
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Is there a dimensioned sketch available?
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ionlyski
Trad climber
Kalispell, Montana
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Mar 24, 2015 - 09:54pm PT
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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
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StefanS
Trad climber
Leavenworth WA
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Mar 24, 2015 - 10:54pm PT
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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.
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Tvash
climber
Seattle
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Mar 25, 2015 - 08:08am PT
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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.
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ionlyski
Trad climber
Kalispell, Montana
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Mar 25, 2015 - 03:10pm PT
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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.
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