Fascinating. It wasn't used as some sort of bell was it? I know that in the cowboy movies, Ma would summon Pa and the boys to their meals by banging on a wheel rim.
Looks to me part of an old belt drive system running off a statick steam engine, engine used just to power another bit of machinery, but what do I know, Great image Babs well spotted;)
As a guess maybe it was used to roll up something, like hose?
Thanks for all your great ideas on what this could be, but I think Peter and Marnie are probably closest. Definitely looks like an old belt drive system and my favourite is a from Marnie - a wim-wam for a gooses' bridle. I'll go with that ha ha.