Make: Tools by Charles Platt

Author:Charles Platt
Language: eng
Format: epub, azw3, pdf
ISBN: 9781680452501
Publisher: Maker Media, Inc
Published: 2016-10-01T04:00:00+00:00

Reinforcing the Shelves

Going back to my list of requirements, the second one cited the tendency of store-bought shelves to sag when books are placed on them. The 18" shelf in this project is very short, and little paperbacks are relatively light, so you won’t see it sagging. But just for future reference, how long can a shelf be, before it does start to sag noticeably?

Answering that question would require knowing what kind of wood will be involved, how much load it will carry, and how thick it is. However, if the length of a shelf increases, I can tell you how much more it will sag, relatively speaking. A bit of math gives the answer (you can skip this if you dislike math).

Suppose you double the length of a shelf, while the load per linear inch remains constant. The doubled length will cause the shelf to sag eight times as much. If you triple its length, it will sag 27 times as much.

This is because the sag is proportional with the cube of the length of the shelf. In other words, if L is the length, the sag is proportional to L x L x L.

But, there is some good news. If you double the thickness of the shelf, you divide the sag by 8. If you triple the thickness, you divide by 27, because, the sag is inversely proportional with the cube of thickness. So, if T is the thickness, the sag is proportional with 1/T x 1/T x 1/T.

Okay, that’s the end of the math.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.