Path: ...!news-out.netnews.com!postmaster.netnews.com!us3.netnews.com!not-for-mail X-Trace: DXC=ilES[39=CSHJ[86dk_ocUDU5[F2hIijDO7J470dMQQ7KJ4R`5ADBYnBZ7F X-Complaints-To: support@frugalusenet.com Date: Fri, 26 Apr 2024 16:15:48 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: OT: central limit theorem Newsgroups: sci.electronics.design References: <662bf69c$0$8484$882e4bbb@reader.netnews.com> <960o2j9atnupo1orp1kk6lquchg4p3g5g7@4ax.com> Content-Language: en-US From: bitrex In-Reply-To: <960o2j9atnupo1orp1kk6lquchg4p3g5g7@4ax.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Lines: 37 Message-ID: <662c0b75$0$8087$882e4bbb@reader.netnews.com> NNTP-Posting-Host: 127.0.0.1 X-Trace: 1714162549 reader.netnews.com 8087 127.0.0.1:50139 Bytes: 2628 On 4/26/2024 3:36 PM, John Larkin wrote: > 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. Ikea has made a number of nightstands over the years that for whatever reason seem to have openings very close to 19", add a couple Middle Atlantic rack rails and you can house all sorts of gear in them: