Yeah, that's the downside, I presume they just used a dimmable motor, but beware, some motors don't spin the same direction each time, you could be going back in time, not forward. If you do want to go down the path of motors have a read of
this thread, shoud give you some ideas. I know the giant clock esists, as I have seen them, they have about a 1m radius, it wouldn't be too hard to remove the current motor and replace it with a dimmable one.
Nick