I bought a couple of DC motors a while back that were about the size of a 1/2 AA battery. Pretty small, I thought. Looks like they are monsters compared with this: http://www.bbc.co.uk/news/science-environment-14763223
"It is one of the happiest characteristics
of this glorious country that official utterances are invariably
regarded as unanswerable."
-Sir Joseph Porter, First Lord of the Admiralty (HMS Pinafore)