A wristwatch is one of the most efficient mechanical marvels that I know.
Let's change that and build a large and powerful engine, revving at incredible speed, preferably with twin turbos; variable valve control; air injection and twin overhead cam, which is geared down to drive a set of hands.
Simply by filling up the tank, several times per day, it keeps reasonably good time.
Beside it is a cheap Casio digital watch as a reference.-- Ling, May 25 2008 Steam Clock http://www.youtube....watch?v=75sl0FVTOFA [Amos Kito, May 25 2008] Most powerful diesel engine http://people.bath.ac.uk/ccsshb/12cyl/108,920 HP! [Voice, May 26 2008] I am assuming that the clock is designed to be read through a telescope from Mars, just so the little green men know when we are asleep? It makes it easier to attack when no-one is awake.
+ for sheer crazy factor. But only if the said 800hp engine is a modern V8 with only a resonator either side for an exhaust.-- BLSTIC, May 25 2008 I think I'd prefer a hydroelectric clepsydra.-- MaxwellBuchanan, May 25 2008 But what kind of E.T.s could this clock run?-- MikeD, May 25 2008 //I think I'd prefer a hydroelectric clepsydra//It'd take a course of strong antibiotics to clear it up,though. Or yoghurt.-- AbsintheWithoutLeave, May 25 2008 How about a very-much geared down gas turbine ?-- 8th of 7, May 25 2008 I suggest you move this to category: clock: wristwatch: combination.-- zeno, May 25 2008 800hp isn't enough. Add a dozen transmissions and a precise timing device to a ship's diesel engine...-- Voice, May 26 2008 Nice. It stands to reason, that, for a reasonably sized clock face, almost all of the power (800BHP, some 600 kilowatts or so) will be consumed by friction in the gearbox. That's a lot. This thing'll be 90% oil cooler, 8% gearbox, and 2% engine.-- Custardguts, Jun 02 2008 random, halfbakery