Torsion-box shelves

[andsally]

Hi all.

I am designing a two built-in bookcases, using torsion-box shelves that will be permanently fixed to sides and rear.

The shelf span will be 1040mm (3ft 5ins) and the depth will be about 220mm (9ins). Each shelf will be filled; the typical load on each would be between 25kg (55lbs) to 55kg (120lb) with NO bowing.

Ideally, I would like to dispense with centre vertical supports and rely upon the strength of torsion boxes. Have posted an initial plan below: top and bottom faces are 12mm MDF, with a timber core framework of 18x28mm. Instinct suggests this may be ok for the lower load but I am unsure about the higher figure.

It has been a while since I last worked with torsion-box shelves with heavy loads. Can anyone please assist?

Thanks


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[chippie244]

Google The Sagulator

 

[andsally]

Thanks for that - I did try the Sagulator page but it couldn't specifically help with torsion-box construction.

I have now made and fixed ten of them, each 1020 x 260 x 36mm, using 6mm ply top and bottom skins, with 28 x 18mm battons. I can stand on them and have confidence that they will not sag with the books they will house.