Mrs. Dvl and I are looking to build couple bookshelves to flank the fireplace in our parlour. Each will be eight feet long and a foot in depth. We’d like to use dowels for the vertical support.
We will drill six holes in each horizontal board, two near each end and two in the middle:
(looking down from the top)
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We will drill holes along the height of the vertical dowels, and insert pins in each one to create supporting crossbars (one for each level of shelving):
The individual shelves will then slide over the dowels, and rest on the pins.
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I hope that made sense… I’m not an ASCII artist.
I’ve seen this done with thick wooden dowels (stained closet rods, I think) as the vertical supports. What we’re trying to figure out is:
[ul]
[li]if copper tubing will be strong/rigid enough to support eight feet of books (divided among six support columns);[/li][li]if so, how to figure out the needed diameter of tube; and, [/li][li]whether or not driving pins through the tubes will throw all of the above out the window. [/li][/ul]
In compression, probably just fine. I’d be concerned about any side loads causing a tube to buckle, so forget all about using 1/2" pipe.
Just visually, I can’t imagine anything smaller than 1" looking right scale-wise, ignoring strength, and 1" ought to be pretty strong, even to a side load. Just to throw a little confusion at you, copper water pipe comes in strengths - Type K is thick-wall, and up the alphabet, the stuff gets thinner. For this, it’s probably worth seeking out Type K since you’re using it structurally, rather than just to carry water.
How were you planning to anchor the pipes at top and bottom?
The three failure modes you’re going to have to worry about are the whole shebang bending over sideways (like dominoes), with the tubes buckling at the holes you drilled through them; a possible bearing failure of the copper where the crosspins rest in the holes in the tubes; and shearing of the crosspins.
To prevent the first, you could either add diagonal braces to the backs of the shelves, or fasten the upper ends of the tubes to the ceiling.
To prevent the second, you would use fairly large-diameter crosspins (to increase the bearing area against the edge of the holes).
To prevent the third, you’d use large-diameter crosspins or make them of metal.
If it were me designing it, I’d use one-inch copper pipe, 1/4 inch aluminum rod for the crosspins, and I might reduce the distance between supports to help prevent the shelves from sagging. I’d use 3/4 inch thick pine for the shelves, with a piece of 1 1/2 inch wide strip glued (and rabbetted–I think that’s the term) to the edges to make them stiffer and to give them a more substantial look. I’d fasten the uprights to the ceiling using pipe flanges.
Disclaimer: IANA Engineer, but I do hang out and build random shit with a lot of them…
That would be my worry. Books are heavy, and you’ll have all that weight on the hole where the pins go through the tube, and copper is pretty soft… If your shelf wobbles a bit, it’ll be really hard on the tubing at that joint over time. I’m not sure how it could be reinforced or improved, though… maybe the use of some sort of plumbing joints that are soldered on, instead of pins? You couldn’t take that apart, though…
Perhaps you could get the desired cosmetic effect (which I wholeheartedly support… copper can look really good IMO) by using the normal wood dowel design, with thin walled (and cheaper) copper pipe slid snugly over the dowels. You’d have to come up with some variety of pipe with an ID that matches an appropriate dowel diameter, but I bet you could come up with such a combination without too much trouble.
I hate to admitted after all of your ASCII art, but I’m not clear where the copper tubing comes in. Are you planning on using tubes as the pins, or as the vertical supports, or what? I’m going to assume that you’re talking about them as vertical supports.
In any case, copper is really a rather poor structural material; it’s soft and prone to bending. It’s also rather expensive; from this price chart (warning: PDF) 3/4" OD copper tube (1/8" wall) of Type M hard tubing is $2.90/ft. If you use, say, 60 feet of tube then you’re well and beyond the price of an IKEA shelving unit, not even counting the cost of wood. And plumbing copper is going to have spec information preinted on the outside, so not all that decorative except in the post-collegate haven’t-discovered-real-furniture sense. Buckling of the tube would probably occur if you loaded up all the shelves, but for the sake of simplicity (and because all the stress concentrations you’re introducing will make an Euler buckling calculation totally useless) we can just consider the case of failure from bearing, in which case…forget about it; you’re definitely going to exceed the bearing strength.
One note about the design; assuming the vertical supports are each freestanding, you’re going to to make the holes in the boards with very tight clearances (and thus, very accurated reproduced on each shelf) or the thing is going to have a tendency to wobble. It would be best if you could either fasten the supports to the shelves, at least at the top and the bottom, or otherwise tie them together (perhaps with wire rope, tensioned by turnbuckles) to keep it tight.
I think it would work assuming that you braced it to prevent sideways movement, and yo made a minor change in the design of the side pins.
Instead of drilling for side pins, cut the tube, and install a copper cross joint.
Of course I can’t find a link, so they may not be available. Never mind.
3/4 inch threaded steel rods with washers and lugs nuts screwed to the same levels for each board for 5 boards was my bookcase for years.
You can use 1in. thin-walled copper tubing as a sleeve over 3/4 inch threaded steel rods for cosmetic effect. For your design specifically, you could still drill cross holes, and with the steel they would probably work (just a pain to drill through threaded steel - pay someone else to do it if you don’t have the right tools). But, with threaded lugs and washers above and below each level you can make the whole bookshelf rigid and secure. You can use two flat bars of metal for the washers of one level, on the back sticking out, and then attach a cross bar between those bars for added stability, or use to attach to the wall (which is what IKEA says to do with all of its stuff).
What type of wood are you going to use? Industrial with the laquered plywood, or ???
Fine steel wool, once a year, keeps it all gleamy. That’s on the copper conduit (1.5"D) towel racks I put up in my bathroom. Conditions there are probably harsher than in a parlour, however if it’s a real concern, you can polish the stuff, and then give it a spray of clearcoat.
I suspect Stranger is thinking something similar, but to expand, what is going to resist twisting forces on the whole shebang? You could fasten it to the wall, I guess.
One important note: it’s a good rule of thumb that you don’t want to ever drill a hole through a support that exceeds one-third of the support’s primary dimension. Quarter-inch steel is plenty strong (overkill, really - think if the 1/8" steel pins that come with an IKEA shelf) if you use it at all four corners of a given shelf, or take care to distribute the loads. If you wanted a shelf that looked very lightweight, you could put 3/8" steel stock inside 1/2" copper pipe, drill them both, and nest them. You need to be very worried about the “domino” mode of failure. Something at the top and bottom sets of joints needs to be a rock-solid right angle, or you will end up with books scattered around the base of a bizarre-looking modern sculpture in your living room.
Sure Bosda, if you’re will to settle for a cheesy semi-matte finish, and paint flakes on your towels.
Properly cared for copper gleams like nothing else.
On one of the home improvement TV shows, the designer built a hanging wood and copper shelf to hold some teapots. The copper and wood both “broke”, sending pottery shards all over the floor. :eek: It wasn’t clear whether it broke because the wood wasn’t strong enough or if the copper broke first under stress.
Thanks for all the input. Alas, it seems that copper support structures are looking more and more iffy—unless someone comes along and posts a nice, easy to use (i.e., with decades-old college math skills) sure-fire formula for tube strength, it sounds like too much of a risk. Who wants fifty linier feet of books, wood, and tubing crashing down in front of the fireplace?
We’re still looking to incorporate copper into the project. It seems to be one of those ideas that gets stuck in our craw and is looking for an outlet. We’ve moved to using wooden dowels (1" in diameter) for the verticals, with wooden pegs (i.e. cut from smaller dowels) as supports. For the copper look, we’re thinking to get tubing to clad the support pins (probably 1/2" thin-walled tubing, and sanding down the pins to fit the interior diameter).
As for stresses:
Since the horizontal boards (1" pine) are rigid, won’t six shelves worth provide enough stability to keep it from moving laterally? That is, for the whole structure to lay down sideways, won’t lateral forces have to overcome thirty-six inches (one inch per shelf, six holes per shelf) of wood? We’ll be using a drill press and some maniacal measuring to make sure the tolerances are tight. Are diagonal cross members needed?
As for it tipping toward us, we’re going the IKEA route – we’ll be placing a few hidden braces into the wall studs to keep the structure flat against the wall.
Now that we’re going all wood, would anyone care to comment on our thought that one-inch vertical dowels (six per shelf) with half-inch support pins will be strong enough?
Thanks,
Rhythm
Oh… since the bookshelves contain the Hitchhiker’s series, considerations about towels are necessary.
The problem is that you’ll basically need a press fit or the whole thing will tend to wobble and sag. For a lightweight table this might be acceptible, but for a large shelving unit not such a good idea.
Are there just two shelves, or more? I looks like you’re going to have a free span of 3’-4’ inbetween the supports; for a short pair of shelves that should be fine, but for a true bookshelf with four or more shelves I think you’re going to want more supports or more sturdy supports.