Tensile strength of all thread

[qmdv]

So if hanging a load from 1/2 13 all thread, I think I compute the max load this way. The tensile strength is 50,000 psi. So the tensile stress area from this chart
https://mechanicalc.com/reference/fastener-size-tables is 0.1419.

Guess I multiply that times tensile strength that is 7095 pounds. If I assign a safety factor of 25% and hang a pad eye with four pieces of 1/2 13 all thread I can hang 7095 pounds. Assuming my math is correct

 

[BillK]

Not sure exactly what you mean by this ....

hang a pad eye with four pieces of 1/2 13 all thread

But the 7095 lbs is correct for the tensile strength of the all thread.

 

[Ironcrow]

Yes, if the load is equally distributed. i.e. each all-thread is carrying its fair share. For an application like this I'd use a safety factor of 10 not 4.

 

[jkeyser14]

So if hanging a load from 1/2 13 all thread, I think I compute the max load this way. The tensile strength is 50,000 psi. So the tensile stress area from this chart
https://mechanicalc.com/reference/fastener-size-tables is 0.1419.

Guess I multiply that times tensile strength that is 7095 pounds. If I assign a safety factor of 25% and hang a pad eye with four pieces of 1/2 13 all thread I can hang 7095 pounds. Assuming my math is correct

That is correct, but assumes 100% tensile load and no rust, defects in the rod, etc. Also any side load could have a large effect the longer your all thread it. Typically anything rated for lifting applications has extra inspections and is engineered for a safety factor of 5 or more.

Also, if it was me doing the engineering, I would use the minor area instead of tensile area. You never know if the threads were formed perfectly to spec.

 

[qmdv]

The actual use is to hang a wide flange I beam on 12 foot centers frome engineered trusses. The I beam is 22 pounds per foot. So each truss will have to hold 264 pounds of beem. Pluss a hoist and trolly for about 30 pounds. Lets round that up to 300 pounds total. Using a factor or ten each truss will be able to carry 2838 pounds. Looks like the one ton hoist I h ave will be just right.

 

[qmdv]

Also, if it was me doing the engineering, I would use the minor area instead of tensile area. You never know if the threads were formed perfectly to spec.

Using a safety factor of 10 should more than make up for any of this.

I used to ride around in a fast attack submarine and it had a test depth and a calculated crush depth. When we went deep we could here the hull making terrible noises as the hull contracted. Safety factor is important

 

[matt_i]

The actual use is to hang a wide flange I beam on 12 foot centers frome engineered trusses. The I beam is 22 pounds per foot. So each truss will have to hold 264 pounds of beem. Pluss a hoist and trolly for about 30 pounds. Lets round that up to 300 pounds total. Using a factor or ten each truss will be able to carry 2838 pounds. Looks like the one ton hoist I h ave will be just right.

Imo the hanger rod is near last on the list of things to be worried about.

How to connect to trusses, was each truss designed for an additional 5000# point load, how to connect to the W-beam, was the W-beam selected for less than L/360 deflection, how to manage end-loading of the beam as the load is trolleyed, what load are you going to proof test it with, are a few things that come to mind. This is a good first step but its also a little more complicated than figuring out axial tension that can be borne by a threaded rod. I would pick Grade B7 over the garden variety Grade 2 (that's a guess, its unknown) that's widely available. I'm also impressed you found a hoist + trolley thats 1/2 ton rated for 30 lbs. Seems like the 3/4t trolley I had out a week ago was like 20 lbs by itself.

 

[qmdv]

Yeh I know it is harbor freight but it is the first that came up in the search https://www.harborfreight.com/1-ton-chain-hoist-996.html It is 21 pounds.

Not sure where 5000# additional load came from. Beam is 22 pounds per foot and will be supported every 12 feet. Trolly and hoist is 30 pounds. Max load is 2000 pounds. Looks to me 2500# is about right. A licence engineer designed the truss for the load.

 

[jmarkwolf]

McMaster Carr has 150,000 psi all-thread.

https://www.mcmaster.com/threaded-rods/threaded-rods-and-studs/high-strength-steel-threaded-rods-8/

 

[qmdv]

McMaster Carr has 150,000 psi all-thread.

https://www.mcmaster.com/threaded-rods/threaded-rods-and-studs/high-strength-steel-threaded-rods-8/

50,000 gives a safety factor of 10 Not sure I need a safety factor of 30.

 

[WNYflyer]

Imo the hanger rod is near last on the list of things to be worried about.

How to connect to trusses, was each truss designed for an additional point load

^This, 4 - 1/2 diameter bolts would typically be the least of the worries for that size hoist.

A licence engineer designed the truss for the load.

Good that engineer designed the truss for the load but did he tell you how and most importantly the location(s) on the bottom chord of the truss where you can make the connection ? Typically you try to have a panel point of a truss at the location of the monorail so to basically eliminate bending of the bottom chord due to a monorail/point load which would occur if the monorail was placed between panel points. Locating a monorail at a panel point of the truss more often than not doesn't work out layout wise so the bottom chord of the truss is designed for the bending induced by the monorail/point load placed between truss panel points. For existing trusses sometimes after the fact additional truss diagonals are added that meet at the monorail mounting point so as to minimize the bending in the bottom chord and transfer the monorail point load efficiently to truss vertical members.

 

[matt_i]

My 5000# was your 1000# working load x safety factor of 5. Appropriate for overhead lifting. There can be unintended things happen like jerk or bounce that induces larger-than-static loads, hence the safety factor to account for this. A crane system would typically be certified (load tested) at 125% of working so some is needed just for that as well.

Its also important to be concerned about the side loading that the rolling load places on the structure. If the hanger rods are more than say 2-3" long there is going to be sway in the monorail as the load is trolleyed, and that also transfers to the structure. X-bracing is a good way to solve it but make sure the structure is braced as well. The goal is to share the load amongst many members.

 

[BillK]

Just curious . . . . what exactly are you planning on lifting with this ?

 

[qmdv]

My 5000# was your 1000# working load x safety factor of 5. Appropriate for overhead lifting. There can be unintended things happen like jerk or bounce that induces larger-than-static loads, hence the safety factor to account for this. A crane system would typically be certified (load tested) at 125% of working so some is needed just for that as well.

Its also important to be concerned about the side loading that the rolling load places on the structure. If the hanger rods are more than say 2-3" long there is going to be sway in the monorail as the load is trolleyed, and that also transfers to the structure. X-bracing is a good way to solve it but make sure the structure is braced as well. The goal is to share the load amongst many members.

Beam will be held tight to bottom of truss so it will not be swinging back and forth. I have a one ton hoist so I want to be able (if only once) to lift that ton. Thanks folks. This all goes to engineer later this week. If engineer says limit it to 3/4 ton that is what I will do

Out

 

[BillK]

Considering that guys pull complete Big Block Chevy marine engines (easily 800 lbs) out of boats with a plate bolted to the intake manifold with four 5/16" bolts, I simply cant imagine what you are using not being strong enough

 

[rburke65]

Would like to see some photos of this project....please! Thanks BillK.

 

[matt_i]

Considering that guys pull complete Big Block Chevy marine engines (easily 800 lbs) out of boats with a plate bolted to the intake manifold with four 5/16" bolts, I simply cant imagine what you are using not being strong enough

This might not be as light duty as you think:

The 5/16-18 has a minor dia of .243" per tables.

pi/4 * d^2 gets us in the neighborhood of .046 in^2 minimum cross sectional area per fastener.

In 4 fasteners that's a total of .185 in^2 total area.

The 1/2-13 has a minor diameter of .404" per tables.

pi/4 * d^2 = .128 in^2 for a single fastener..


So......its actually more conservative (meaning lower stress on the steel) to lift an 800 lb fully dressed big block with 4 * 5/16-18 fasteners than it is to lift 1000 lbs with a single 1/2-13.....

 

[BillK]

So......its actually more conservative (meaning lower stress on the steel) to lift an 800 lb fully dressed big block with 4 * 5/16-18 fasteners than it is to lift 1000 lbs with a single 1/2-13.....

Yes but he is talking about using four 1/2" rods

 

[matt_i]

Yes but he is talking about using four 1/2" rods

I must have missed it in the design, I was thinking in a monorail that its entirely likely that one single hanger rod can hold the entire working load if the trolley is rolled right underneath.

If four rods are used per hanger then it should be very well supported!

 

[Showkey]

Material Strength – 60,000 psi J82 60M or Grade 1 or Class 4.8

5/16-18 0.3125 3,144 lbs

TS is Obviously not working load.

 

[nadogail]

Over Built is Under Rated or, as an old-timer once told me, "If you have doubts, Build For Stout".

 

[MoonRise]

A 'standard' safety factor might be 4.

(except for aircraft where it might be 1.25 but then it is inspected and reinspected regularly.)

For overhead lifting (cranes, hoists, etc) the usual safety factor is 5 or where a man-safe rating is required, then the MINIMUM safety factor is usually 10.

https://en.wikipedia.org/wiki/Working_load_limit

And proof testing is usually done at 125% of the rated load (WLL).

1/2-13 thread with a 36ksi yield should have a yield strength of 5652 lbs. No safety factor yet. Safety factor of 5 gives a 'safe' WLL of 1130 pounds. Overhead man-rated with a FS=10 means your WLL is 562 lbs.

Does your lifting scheme ever have all (or most of) the load supported by just one or two rods? Big difference if the load on the trolley is at an end of the beam and 'hanging' pretty much from just one threaded rod compared to a load case of a uniform load distributed over the entire beam and shared by all the threaded rods.

Dynamic loads? The weight swings a bit or bounces? Not the same load case as a completely static load.

And as mentioned by Matt above, there are the beam-to-truss connections, the truss-to-support-post connections, the support-posts-to-the-foundation connections, etc.

Why not just get a separate gantry crane and not deal with trying to make a crane out of your building?

Like this:

https://www.harborfreight.com/1-ton-telescoping-gantry-crane-41188.html

Or other gantry cranes?

 

[Steve_P]

Buy threaded rod from McMaster that is strength rated. Not Home Depot

 

[WNYflyer]

Buy threaded rod from McMaster that is strength rated. Not Home Depot

I just checked Ace Hardware's website and the threaded rod carried in the local store has an actual specification of ASTM A307 which is a very common material and similar to another common material of ASTM A36.

Have no idea why Home Depot doesn't show the material specification on their website for their like product, perhaps the store shelf indicates it but I highly doubt that. Given the choice I would be buying from the place that attempts to actually indicate the actual material.

 

[Borntoolate]

Without a sketch of all this it is very difficult to comment with much assurance. I am guessing that if a sketch were provided that half the folks on this thread might say something like "oh, that is not what I was thinking..." Not trying to be a **** but this is my experience with things of this nature. Dimensioned drawings go way farther than words when attempting to engineer a design.

 

[Borntoolate]

I just checked Ace Hardware's website and the threaded rod carried in the local store has an actual specification of ASTM A307 which is a very common material and similar to another common material of ASTM A36.

Have no idea why Home Depot doesn't show the material specification on their website for their like product, perhaps the store shelf indicates it but I highly doubt that. Given the choice I would be buying from the place that attempts to actually indicate the actual material.

Most bolting type materials have the specification stamped on one end of the bolt or head. All-thread may be different especially from the box stores... IT may be a letter or number...

 

[GMCGarage]

Over Built is Under Rated or, as an old-timer once told me, "If you have doubts, Build For Stout".

When in Doubt, make it stout.
Cant tie a knot, tie alot.
Just a few things that I use all the time.