Homemade scales

Last month, I mentioned that I was selling a lot of stuff using eBay – mostly games, but also DVDs, books, phones, etc. By using the Royal Mail’s online postage printer, I was able to avoid visiting the Post Office. The only problem is that I don’t have my own scales.

For most items, you don’t need scales. The Royal Mail has a nifty weight comparison guide that tells you the approximately how much common items like books, DVDs, CDs and phones weigh. It tends to overestimate weights, but it’s good enough. When it comes to uncommon items, however, you need to find another solution.

I eventually hit upon the idea of using my steel ruler as a beam, a bed railing as a fulcrum, and an object of known weight as a counterbalance. A good source of objects with known weight is the kitchen, but if you’re looking for something lighter than a bag of sugar or tub of margarine, you have to be a bit more imaginative. It turns out that pretty much all modern consumer electronics such as digital cameras, mobile phones and MP3 players have their exact weight recorded on the web, typically in product reviews and specifications. The weight of my Nokia N73, for example, is exactly 116g. Put the N73 on the ruler, put the object whose weight you want to know on the other side, and you can figure out whether it’s lighter or heavier.

If you want to be exact about it, you can always start measuring the moment of the forces and so on (which is why it’s useful to use a ruler) but I find that only a certain amount of precision is required.

One of my abandoned ideas was simply weighing two objects in either hand and trying to figure out which was heavier. Apart from being a rather boring and unscientific solution, I decided that I would be too vulnerable to the size-weight illusion and gave it up.

All of this was rendered moot when my girlfriend bought me a very shiny electronic balance for my birthday, but here it is, mostly to be a service to the scale-less among us, and partly to convince you that there’s more to my life than tirades against publishers and the BBC…