Vertical torsion boxes for bookcase: good idea? - Router Forums
 
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post #1 of 8 (permalink) Old 07-26-2010, 11:29 AM Thread Starter
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Default Vertical torsion boxes for bookcase: good idea?

Hi - I am contemplating making basic bookcases from 1-1/2" thick material. Using solid wood would make the cases very heavy (and too expensive), so I was thinking of using some sort of torsion-box design. I know torsion boxes are often used for horizontal shelves, tables, etc., but I am thinking of also using them for the cases themselves, i.e., also for the vertical sides.

I was wondering if there is anything special regarding stability I need to consider. Obviously, a lot of doors are designed like torsion boxes, but I am not sure about attaching shelves to the sides. The skins will be rather thin (1/2" or even 1/4"), and so I will need to think carefully how to best make the shelves adjustable (ideally).

Perhaps it would be easier to simply use two layers of 3/4" plywood and dress up the edges, but that again would be very heavy.

Any advice?

Thanks! MM
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post #2 of 8 (permalink) Old 07-26-2010, 12:22 PM
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I would think by the time you have added in all the extra material for the torsion box and then skin both sides or one side then face frame the other side and I would guess the weight with all the extra wood would be about the same over all that it would be about the same as the standard style in price due to extra construction time and materials used, sometimes reinventing the wheel just is not needed and the basic construction of a dado bookshelf works just fine.

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Last edited by newwoodworker; 07-26-2010 at 12:25 PM.
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post #3 of 8 (permalink) Old 07-26-2010, 01:04 PM
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Originally Posted by xvimbi View Post
Hi - I am contemplating making basic bookcases from 1-1/2" thick material. Using solid wood would make the cases very heavy (and too expensive), so I was thinking of using some sort of torsion-box design. I know torsion boxes are often used for horizontal shelves, tables, etc., but I am thinking of also using them for the cases themselves, i.e., also for the vertical sides.

I was wondering if there is anything special regarding stability I need to consider. Obviously, a lot of doors are designed like torsion boxes, but I am not sure about attaching shelves to the sides. The skins will be rather thin (1/2" or even 1/4"), and so I will need to think carefully how to best make the shelves adjustable (ideally).

Perhaps it would be easier to simply use two layers of 3/4" plywood and dress up the edges, but that again would be very heavy.

Any advice?

Thanks! MM
This is very possible to build but (as was said) may require more time/work/effort to make it right. I bnought a shelf like this and I thought it was solid until I picked it up. it looked good and was not heavy. It was covered in 1/8" luan and it was painted to look like antique wood. It had adjustable shelves using small brackets in a slotted rail (like this: Shelf Support Strip).

I assume you want the 1-1/2 inch thickness for styling reasons but are asking about hollow construction because you don't want the weight. One other advantage about hollow construction is that you could use inexpensive pine (SPF) for the internal structure and cover it with a thin sheet of whatever you want.

Another alternative is to just make it using 3/4" stock as was described and add molding, or edging to give the appearance of the added thickness on the outside. When you look at the shelves on the inside, you would see that they extend past the molding but this might be acceptable. You could also fill this area but then you would loose the adjustment capability.

If the above will not work for you, you could build a frame latice out of 2x2, or double thick plywood with square holes cut out, and cover it with 1/8" thick sheet product of whatever wood you want. The 1/8" will seem a little flimsy if you rap on it but it will look fine. You could use thicker sheet product and a thinner latice frame but I think 1/4" sheet covering would be the thickest you would need. For whatever adjustment capability you build in (pins, brackets on a rail) just make sure it's located where your latice frame is.
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post #4 of 8 (permalink) Old 07-27-2010, 08:43 AM
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Considering the weight of books, I don't think the the weight of the case itself should be a consideration.

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post #5 of 8 (permalink) Old 07-27-2010, 10:20 AM
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Considering the weight of books, I don't think the the weight of the case itself should be a consideration.

Good point - but what if it needs to be carried up some stairs? People have reasons for specific requirements. A group of 10 people will have 12 opinions about the same thing.
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post #6 of 8 (permalink) Old 07-27-2010, 10:35 AM Thread Starter
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Thanks for the replies so far.

Indeed, it's all about weight. We have some 'normal' bookcases made from 3/4" material that already are quite heavy. The stairs to our second floor are long and steep. Also, we want to avoid using molding or face frames for style reasons.

I realize that using a hollow-core design will require more work, but that might be acceptable. I just want to do it right if I go that route. Another option would be to make smaller units that could be assembled in a modular fashion in all kinds of configurations. Ah, it's good to bounce off ideas!

Thanks again! MM
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post #7 of 8 (permalink) Old 07-27-2010, 10:48 AM
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I agree with the 3/4" ply solution. Two thick won't be much heavier unless you go with 1/4" construction. Another option would be increasing the thickness to 2". Two half inch ply with 1 1/2" frame in dadoes. The dadoes will give extra support internally and it would be rock solid. Last time i saw something like this, it had adjustable shelves with thick main shelves at the bottom, midpoint and top held together with pins and keyholes. I'll draw you up something if you'd like. For a better visual.

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post #8 of 8 (permalink) Old 07-27-2010, 08:05 PM
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You didn't say rather or not you intend on placing this "upstairs". Since, you did mention stairs, I'd like to point out that, many have "turns" that for certain objects just won't make those turns. Book shelves are no exception. You can build "in place", meaning a lot of trips up an down stairs or, as you mentioned. Smaller units that could be a "break-down" bookshelf.

Ken

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