A new Canadian mystery

Another Canadian mystery 

On a recent hunting trip in North Western Ontario, I noticed these two large drum like objects by the side of the road. Naturally enough, Australians would tend to think of them as water tanks - but no, this is Canada and they don't need water tanks. So what are they? And what purpose do they serve? 

Here are a couple of clues to help you along: 

1. Both 'barrels'can turn easily on their base.

2. The bases are cantilevered to allow the structures to move apart and return.

The last piece of information is less a clue than it is a recognition of the maker - some bloke in Thunder Bay invented these.

So, what's your best guess?