Category Archives: Engineering

Kids longbows

Posted on by
Reply

My eldest daughter asked me if we could make a bow and arrow for her. She’d done some designs and wanted to make them.

We watched some videos on YouTube on how to make bows and had a go. The first attempt broke.

Broken bow. Wood wasn’t great and was too thick when I test pulled the bow.

So we tried a different approach. I’d cut down an Ash sapling in the garden a few months ago – we’ve got Ash trees at the bottom of the garden so we get saplings growing everywhere. The top of this was about the right stiffness for a bow. So we cut off a suitable length and started work.

Trimming the side branches with an axe – watch those feet!

There are some key design points to making a bow. Any wood that is weak enough to bend is likely to break, so the idea is to trim the wood in such a way that it is still strong, bendy but doesn’t break.

Continue reading →

Vitruvius on lead pipes

Posted on by
Reply

I recently received a copy of Vitruvius’s On Architecture. This is a guide for professional engineers written in about BCE10. Vitruvius worked for Julius Caeser and was granted a pension by Augustus.

The first impression is of a modern attitude towards engineering. Whilst some of the conclusions are not in alignment with modern thinking the overall impression is that you could take this book, follow the instructions and the results would be satisfactory. The theory as to why you should do certain things is dubious, but the conclusions seem sound.

I’ve only browsed the book so far, but my biggest surprise is that he says lead pipes are poisonous:

Besides, water from terracotta pipes is much more healthy than that taken through lead pipes, which seems to be particularly damaging seeing that white lead, said to be harmful to the human organism, derives from lead.

…

So it is obvious that water should never be conducted in lead pipes if we want it to be beneficial to our health.

This was over 2000 years ago. I’d always thought that lead being toxic was a modern discovery. I grew up with:

  • Leaded petrol
  • Lead in paint
  • Lead water pipes (lots still around and in use)

So I am boggled that lead was known to be a problem over 2000 years ago!