Path: Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Fri, 26 Apr 2024 19:38:01 +0000 From: John Larkin Newsgroups: sci.electronics.design Subject: Re: OT: central limit theorem Date: Fri, 26 Apr 2024 12:36:09 -0700 Organization: Highland Tech Reply-To: xx@yy.com Message-ID: <960o2j9atnupo1orp1kk6lquchg4p3g5g7@4ax.com> References: <662bf69c$0$8484$882e4bbb@reader.netnews.com> X-Newsreader: Forte Agent 3.1/32.783 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 30 X-Trace: sv3-m138gOLaoXa4LGzvswe8Pcq/iqSv5EwBnlpU7UBBsd0UVtM1521CXWxYGn2PIjTWiJO3sT2xkN5fT7s!mZjnQrQLmat9OE9BtEHx+zzfaos/Rrl6YgBgj3Vg3qLOoVhgJQCv5yL4qTquRF7tfiOadJNDTmoR!kNRLYQ== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 2392 On Fri, 26 Apr 2024 14:46:52 -0400, bitrex wrote: >I have one of these inexpensive Ikea bookshelves for storing some of my >electronics books: > > > >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.