I have tried to use rio gem to download a zip file (in windows) but it 
results in a corrupt d/l. I think this is because binary mode is not 
available in rio.
So I am now trying to use open-uri

require 'open-uri'
f = open (url)

f  is of class  tempfile.  How do I save this temp file to disk?
Does open-uri have a binary mode option, or is it the default?

Or is there a more elegant ruby way to d/l binary mode files ?

Thanks
Paul Fraser