Once again no need to get hostile.

Read your blurb from that book again. It's a "clutch," not a clutch. The author uses the word "clutch" so that the reader can understand the operation of the unit, not to state that a viscous coupling in fact has a clutch. Note that there is no mechanical contact. There is no such thing as a clutch which does not make some form of mechanical contact.

I'm not trying to school anyone here. I'm a moderator of this forum which means I'm supposed to correct what I feel is improper information. Please try and refrain from tossing around insults because I have disagreed with you.