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From: John Larkin <jjSNIPlarkin@highNONOlandtechnology.com>
Newsgroups: sci.electronics.design
Subject: Re: OT: central limit theorem
Date: Fri, 26 Apr 2024 12:36:09 -0700
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On Fri, 26 Apr 2024 14:46:52 -0400, bitrex <user@example.net> wrote:

>I have one of these inexpensive Ikea bookshelves for storing some of my
>electronics books:
>
><https://www.ikea.com/us/en/p/laiva-bookcase-black-brown-40178591/>
>
>I noticed the center shelf was starting to sag a few degrees. :( The 
>assembly manual specifies a weight limit of 33 lbs evenly distributed 
>which seemed like an oddly specific number. So I weighed the books on 
>the shelves, which aren't particularly well organized other than to 
>fully fill the available space widthwise on each shelf.
>
>A random assortment of hardbacks and paperbacks, some are tall and 
>skinny, some are short and fat. And each shelf was clocking in at 33 lbs 
>+/- 2 lbs.
>
>So I guess a heuristic for filling these shelves is just fill 'em up 
>then remove the heaviest book, and de-rate the center shelf by maybe 5- 
>10 lbs because it's unsupported by a backing.

Composites, like the Ikea particle board, tend to sag. I got a nice
barbeque table where the propane tank can sit on the lower shelf, but
in a matter of days it took on a serous sag. It's some plastic
composite.

Like many things that one buys these days, the first thing is to
redesign it.

Add a center support of some kind.