Weight of Threaded Rod

[bostonman]

I don't understand from your post if the thing is hanging or standing

The bookcase is hanging, the threaded rods go through the ceiling, and through a 4x4 laid across the attic joists with nuts (maybe I'll use coupling nuts to catch more threads).

You were implying I was suspending it to the A frame (or at least  I thought you were), so I was correcting you.

[coppercone2]

I thought you were building a shelf hanging from the top of the attic in the attic

[bostonman]

No.

The bookcase will be on the wall in the computer room suspended by the rods going through the ceiling and into the attic - this is a 3D image of what it will look like.

[Mechatrommer]

i certainly wont make a bookshelf like that. its so non-portable and installation/removal is more difficult.. any decent house floor, concrete wall or studs can support 500lbs just fine. ymmv.

[ebastler]

The bookcase will be on the wall in the computer room suspended by the rods going through the ceiling and into the attic - this is a 3D image of what it will look like.

Oops -- hold on. All the time I was assuming that you were planning for long rods which go all the way down to the bottom of the shelf, through each of the shelf boards, providing direct support for each board. The way you show it, the top board of the shelf (or its frame, if you want to call it that) will have to carry the full weight, and it will see a significant bending force, not just a push/pull.

What material and dimensions are you planning for that top baord? (Sorry if you already wrote about this and I didn't pick it up; my "rods threaded through all the shelves" mental picture might have been in the way.)

[calzap]

The bottom shelf is close to the floor.  Why not extend the sides down, support it from the floor, and forget the rods?  It would be less work and more portable.   Good idea to have a couple of anti-tilt brackets from bookcase to wall.

Mike

[bostonman]

The picture is an error. The rods would go through all the shelves.

As for wby suspended? I’m just trying to keep things off the floor, make it more open.

[Gregg]

Masonite or tempered hardboard is thin stiff pressed wood fiber material available in 1/8” 3/16” and ¼” sold in any big box home improvement store.  It is available in one smooth side or both sides smooth and is easily painted.  It is good for things like shelf backs and drawer bottoms.
McMaster sells B7 zinc chromate plated medium strength (120K psi or about equivalent to grade 5 or 6 bolts) 
https://www.mcmaster.com/99086a192
To keep the part of the rod in the attic from corroding, just coat it with some grease (or fluid film if you want the best protection).  WD40 is too thin and short lived for this application. A light coat of grease covered with some heatshrink for where the rod goes through the 4x4 may be a good idea because the wood will tend to keep moisture in contact with the rod.

[CatalinaWOW]

So much angst over what appears to me to be a more than adequate approach. 

Just a couple of comments: 

The conversion to a metric calculation may be of use to those who have no access to traditional English units, but is an example of where the purity of metric actually complicates the calculation.  While the metric version eliminates confusion between pounds mass and pounds force, in this simple non-accelerated system there is no difference, hence no confusion.  As pointed out in several prior posts the answer is a the simple product of area times tensile strength in traditional units.

I don't really think a proof test is necessary, but you have seen the variety of opinions here.  Getting a solid theoretical answer will be more difficult than getting empirical results.

You haven't mentioned any interface to the wall.  I would recommend some form of attachment to eliminate any possibility of a rattle or bang from either air currents or vibration from passing traffic.  Such an attachment greatly complicates the theoretical analysis, but the need has often been demonstrated in practice.  There are ways to make said attachment theoretically sound (applies a load to the book case without supporting any vertical loads), but only one is worth considering in practice, which is placing the ceiling end of the threaded rod slightly closer to the wall than the penetrations of the shelves.   The problem with this approach is that I am not aware of any really good way to determine how much closer you need to be.  You can do the geometry to see how much side load is generated, but the data for how much is enough will be non-existent. 

Or you can do what most tradesmen would do and put a couple of wall anchors in and screw it to the wall.  The reality is that these anchors will deform as needed under the vertical loads and it will work.

[coppercone2]

i would just put a normal shelf there and modify it so its screwed to the floor with some molding so you can vacuum around it, its going to be better lol. I assume you want the vacuum cleaner to go around it nicely. IMO its ridiculous to try to save that space.

Or just screw it to the ceiling and route molding around it on a small face plate if it must float. You get more use out of it anyway, because there is no threaded rod in the middle of the top shelf blocking stuff?? Thats going to be annoying to clean anyway... flat surface wipes down nicely and you can poke your hand in there without going around threaded rods.. and its way cheaper then stainless hardware

I think this thread has so much discussion in it because it does not make sense to make it and it does not look that great IMO

oscillating tool + miter block + hand saw can do this really cheap with a few feet of molding without the craziness, you can make a angle block to press an oscillating tool into to make a angle cut in the molding without removing the entire piece if you please, you can probably even cut the pieces at an angle with the saw provided in home depot before you buy them if you bring the saw block to the store if you wanna save on a saw... or just cut a prism out of the shelf so it fits around the molding (possibly using a rasp if you want it snug tight against the molding).

So the top corner of the shelf would be / rather then |.. if you want it perfect you can buy a contour gauge for 5$ , if you don't want to do trim carpentry work with molding

[SkyMaster]

The picture is an error. The rods would go through all the shelves.

As for wby suspended? I’m just trying to keep things off the floor, make it more open.

Are you planning to use a total of four threaded rods, one near each shelves corners?

You could use 7/8" diameter threaded rods, especially if the rods are visible; this would give a "sturdier" look.

I designed and built several bookcases, all my bookcases are made of solid wood, with center dividers to prevent the shelves from sagging.

All my bookcases are floor standing, but I salute your approach to design a bookcase hanged from the ceiling.

 

[bostonman]

I'm using two rods (one on each side), centered front to back, and about 8" from each side.

A computer model showed that using the wood type (Poplar), thickness, weight, etc... the location of the rods (I think it was 8", but I'll need to check) will cause the shelves to sag very little with a full 100lbs on each shelf (which is unlikely since I only have about 250lbs of books).

All my bookcases are floor standing, but I salute your approach to design a bookcase hanged from the ceiling.

Thanks, some people really like this idea and thought my creativity is great. Many of them want pictures of it's complete.

[coppercone2]

it reminds me of a HVAC or something hanging off of factory ceiling beams