Electronics > Projects, Designs, and Technical Stuff
Weight of Threaded Rod
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calzap:

--- Quote from: Gregg on March 12, 2020, 10:16:07 pm ---I have no doubt that two 3/8 inch threaded stainless rods will do the job installed as you described.  Some type of fastening to the wall like you stated will keep the load on the rods from weakening at any point they may want to bend if the shelf sways.
A few things to consider: Stainless nuts on stainless threaded rod can gall and bind; plated steel or brass nuts may be a better choice. Threaded rod has relatively sharp threads all around that can cause damage to anything that is put against them; you may want to consider covering them with plastic or stainless tubing.  If you do cover them, it may save a bunch of money to use steel threaded rod grade 5 or better; stay away from the grade 2 or lower junk that most hardware stores stock. 
The shelves are going to want to sag in the middle.  Installing a back of even something thin like 1/8 inch tempered Masonite will do wonders to help keeping them straight.  A lip on the back of each shelf would help if a back isn’t going to work for you.

--- End quote ---
Yes indeed, stainless threads can gall and bind ... very tightly ... and when and where it's hard to fix.  A few years ago at my ranch, we needed to extend the pipe that takes water out of a canal into the canal itself.  Previously, it ended in a well to the side of the canal, but there were silting problems there.  There was a big strainer to be fastened to the end of the pipe using large stainless bolts and nuts.  See the first picture.  We were doing this at the end of the offseason when the canal was dry, but knew the water could be turned-on at any time. It was a Thursday afternoon when we were installing the stainless bolts and nuts to replace the temporary zinc-plated ones.

Sure enough, the bottom bolt/nut galled and froze tight when part way on.  Decided to wait until Monday morning to cut it because would have no replacement bolts and nuts until then.  And there were more important things to do like installing the support brace for the upstream shield.  Figured irrigation district wouldn't turn on the water on a weekend ... but they did.  See the second picture.  Using an electric reciprocating saw was out of the question.  Waded in with a handheld hack saw, but soon gave up.  Decided the other bolts would suffice until next offseason.  The other bolts did the job.  Bad bolt and nut were replaced in the next offseason.   Water intake has worked flawlessly for more than 10 years.

Mike in California

coppercone2:
consider putting a floor in and using normal shelves. if you suspend from an attic beam consider the effects of snow load and wind load and deformation of the roof and damage that can be caused by falling trees ETC. This might make analysis further complicated.

Then you can use threaded rod as a spacer and put pipe sections between the pieces so the thread does not get compressed. (to avoid flanges).

Also, I wonder if it could lead to a expensive roof leak if its weighed down in a section. I would not mess with the roof. + fire department likes to cut them open if there is a fire, having a shelf suspended from it may cause problems, especially if they are working from a roof ladder arrangement rather then a truck.

Also, bolts near the roof will experience greater thermal cycling.
Mechatrommer:

--- Quote from: bostonman on March 11, 2020, 03:26:08 am ---...psi...

--- End quote ---
eee yucks !!!

P = 70,000psi = 483MPa
d = 3/8" = 0.95 cm
m = weight (kg)
g = gravity 10m/s^2

A = pi.(d/2)^2 = 7.1e-5 m^2
P = m.g / A
m = P.A / g

= 482MPa x 7.1e-5 m^2 / 10
=3441 kg

50% safety (like in aviation) = 1700 kg
4x rod can support 6800 kg evenly distributed.

whats next? torsion/shear/compressive/tensile stress analysis on the supporting rig.. so home will not collapse. ymmv.
bostonman:

--- Quote ---Also, I wonder if it could lead to a expensive roof leak if its weighed down in a section. I would not mess with the roof. + fire department likes to cut them open if there is a fire, having a shelf suspended from it may cause problems, especially if they are working from a roof ladder arrangement rather then a truck.
--- End quote ---

Not sure if I'm confusing my terminology. Attic joists as in the beams that go across the attic that the ceiling mounts to and you walk across when you're in the attic. I think you're referring to the beams (???) that are part of the A frame and what supports the roof.

I plan to lay the 4x4 across the attic joists, and agree, I'd be crazy to mess with the A frame (i.e. roof beams ????).
coppercone2:
I don't understand from your post if the thing is hanging or standing

if you have it hanging you NEED the strength of the rod, if its sitting its only aesthetic decision (you can slip pipe over it). (the idea being that flanged pipe is more expensive, but it would make threaded rod unnecessary)... but slipping pipe over threaded rod thats under tension might be pretty cheap, and look better, be easier to clean, polish, paint, etc. Especially if you make a tiny counterbore for the pipe to sit snugly in (1mm?)
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